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tocMobile_ITEo"><button type=button class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><header><h1>Build a Logos C++ UI module</h1></header>
<h4 class="anchor anchorTargetStickyNavbar_Vzrq" id=get-started-building-a-ui_qml-module-with-a-c-backend-that-runs-in-a-separate-process>Get started building a ui_qml module with a C++ backend that runs in a separate process.<a href=#get-started-building-a-ui_qml-module-with-a-c-backend-that-runs-in-a-separate-process class=hash-link aria-label="Direct link to Get started building a ui_qml module with a C++ backend that runs in a separate process." title="Direct link to Get started building a ui_qml module with a C++ backend that runs in a separate process." translate=no>​</a></h4>
<p>This guide covers building a <a href=https://docs.logos.co/get-started/glossary#module target=_blank rel="noopener noreferrer" class="">module</a> that pairs a QML user interface with a C++ backend plugin. The backend runs in a separate <code>ui-host</code> process while the QML view loads inside the host app (<code>logos-basecamp</code> or <code>logos-standalone-app</code>), so a backend crash cannot bring down the host. This guide is intended for developers who have completed <a class="" href=/core/build-modules/wrap-a-c-library-as-a-logos-core-module>Part 1</a> and want typed, process-isolated inter-module calls from their UI layer.</p>
<p><strong>Before you start</strong>, make sure you have the following:</p>
<ul>
<li class="">Completed <a class="" href=/core/build-modules/wrap-a-c-library-as-a-logos-core-module>Part 1</a> — a working <code>calc_module</code> with the shared library built in <code>logos-calc-module/lib/</code>.</li>
<li class="">Nix with flakes enabled.</li>
<li class="">Basic familiarity with <a href=https://doc.qt.io/qt-6/qmlapplications.html target=_blank rel="noopener noreferrer" class="">QML</a></li>
</ul>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=what-to-expect>What to expect<a href=#what-to-expect class=hash-link aria-label="Direct link to What to expect" title="Direct link to What to expect" translate=no>​</a></h2>
<ul>
<li class="">You can scaffold, configure, and build a <code>calc_ui_cpp</code> module with a process-isolated C++ backend.</li>
<li class="">You can call <code>calc_module</code> methods from QML using a typed replica and <code>logos.watch()</code>.</li>
<li class="">You will be able to build, run, and live-reload the module using <code>nix run</code>.</li>
</ul>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-1-scaffold-the-project>Step 1: Scaffold the project<a href=#step-1-scaffold-the-project class=hash-link aria-label="Direct link to Step 1: Scaffold the project" title="Direct link to Step 1: Scaffold the project" translate=no>​</a></h2>
<p>Create a new directory and initialise it from the C++ backend UI template.</p>
<ol>
<li class="">
<p>Create and enter the project directory:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">mkdir logos-calc-ui-cpp && cd logos-calc-ui-cpp</span><br/></div></code></pre></div></div>
</li>
<li class="">
<p>Initialise from the template:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">nix flake init -t github:logos-co/logos-module-builder/0.2.0#ui-qml-backend</span><br/></div></code></pre></div></div>
</li>
<li class="">
<p>Initialise a Git repository and stage all generated files:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">git init && git add -A</span><br/></div></code></pre></div></div>
</li>
<li class="">
<p>Remove the template's example sources. The scaffolded template includes <code>ui_example</code> files with mismatched class names and IIDs; leaving them causes build errors or plugin-load failures at runtime:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">rm -f src/ui_example.rep src/ui_example_interface.h src/ui_example_plugin.h src/ui_example_plugin.cpp</span><br/></div></code></pre></div></div>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-2-configure-the-module-metadata>Step 2: Configure the module metadata<a href=#step-2-configure-the-module-metadata class=hash-link aria-label="Direct link to Step 2: Configure the module metadata" title="Direct link to Step 2: Configure the module metadata" translate=no>​</a></h2>
<p>Replace the template <code>metadata.json</code> with your plugin's details.</p>
<div class="theme-admonition theme-admonition-info admonition_xJq3 alert alert--info"><div class=admonitionHeading_Gvgb><span class=admonitionIcon_Rf37><svg viewBox="0 0 14 16"><path fill-rule=evenodd d="M7 2.3c3.14 0 5.7 2.56 5.7 5.7s-2.56 5.7-5.7 5.7A5.71 5.71 0 0 1 1.3 8c0-3.14 2.56-5.7 5.7-5.7zM7 1C3.14 1 0 4.14 0 8s3.14 7 7 7 7-3.14 7-7-3.14-7-7-7zm1 3H6v5h2V4zm0 6H6v2h2v-2z"/></svg></span>info</div><div class=admonitionContent_BuS1><p>The <code>calc_module.url</code> input attribute name in <code>flake.nix</code> must match the dependency name declared here in <code>"dependencies"</code>.</div></div>
<ol>
<li class="">
<p>Replace <code>metadata.json</code> with the following:</p>
<div class="language-json codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-json codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"name"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"calc_ui_cpp"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"version"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"1.0.0"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"type"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"ui_qml"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"category"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"tools"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"description"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Calculator C++ UI — QML view with process-isolated backend for calc_module"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"main"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"calc_ui_cpp_plugin"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"view"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"qml/Main.qml"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"icon"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"icons/calc.png"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"dependencies"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token string" style=color:#e3116c>"calc_module"</span><span class="token punctuation" style=color:#393A34>]</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"nix"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"packages"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token property" style=color:#36acaa>"build"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token punctuation" style=color:#393A34>]</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token property" style=color:#36acaa>"runtime"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token punctuation" style=color:#393A34>]</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"external_libraries"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token punctuation" style=color:#393A34>]</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"cmake"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"find_packages"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token punctuation" style=color:#393A34>]</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"extra_sources"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token punctuation" style=color:#393A34>]</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"extra_include_dirs"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token punctuation" style=color:#393A34>]</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token property" style=color:#36acaa>"extra_link_libraries"</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token punctuation" style=color:#393A34>]</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><br/></div></code></pre></div></div>
<p>Key fields:</p>
<ul>
<li class=""><code>"type": "ui_qml"</code> — tells the builder this is a QML view module.</li>
<li class=""><code>"main": "calc_ui_cpp_plugin"</code> — the backend Qt plugin library name (without extension).</li>
<li class=""><code>"view": "qml/Main.qml"</code> — the QML entry point.</li>
<li class=""><code>"dependencies": ["calc_module"]</code> — <a href=https://docs.logos.co/get-started/glossary#core-module target=_blank rel="noopener noreferrer" class="">core modules</a> the backend calls.</li>
</ul>
</li>
<li class="">
<p>Create the icons directory and add a placeholder icon (displayed in the <code>logos-basecamp</code> sidebar when the module is loaded):</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">mkdir -p icons</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"># Copy any PNG here - or generate a 64x64 placeholder:</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">echo "iVBORw0KGgoAAAANSUhEUgAAAEAAAABACAYAAACqaXHeAAAAmElEQVR4nO3QMREAIBDAsFeEN3ziCWRkoEP2XmedfX82OkBrgA7QGqADtAboAK0BOkBrgA7QGqADtAboAK0BOkBrgA7QGqADtAboAK0BOkBrgA7QGqADtAboAK0BOkBrgA7QGqADtAboAK0BOkBrgA7QGqADtAboAK0BOkBrgA7QGqADtAboAK0BOkBrgA7QGqADtAboAO0BN/SiO/PatoIAAAAASUVORK5CYII=" | base64 -d > icons/calc.png</span><br/></div></code></pre></div></div>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-3-define-the-remote-interface>Step 3: Define the remote interface<a href=#step-3-define-the-remote-interface class=hash-link aria-label="Direct link to Step 3: Define the remote interface" title="Direct link to Step 3: Define the remote interface" translate=no>​</a></h2>
<p>The <code>.rep</code> file is the single source of truth for the interface between the QML view and the C++ backend. <code>repc</code> compiles it at build time into typed source and replica headers.</p>
<ol>
<li class="">
<p>Create <code>src/calc_ui_cpp.rep</code>:</p>
<div class="language-rep codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-rep codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">class CalcUiCpp</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">{</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> SLOT(int add(int a, int b))</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> SLOT(int multiply(int a, int b))</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> SLOT(int factorial(int n))</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> SLOT(int fibonacci(int n))</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> SLOT(QString libVersion())</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">}</span><br/></div></code></pre></div></div>
<p><code>repc</code> generates two headers from this file:</p>
<ul>
<li class=""><code>rep_calc_ui_cpp_source.h</code> — <code>CalcUiCppSimpleSource</code> with virtual slots the backend overrides.</li>
<li class=""><code>rep_calc_ui_cpp_replica.h</code> — <code>CalcUiCppReplica</code> with typed methods the QML view calls.</li>
</ul>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-4-write-the-interface-header>Step 4: Write the interface header<a href=#step-4-write-the-interface-header class=hash-link aria-label="Direct link to Step 4: Write the interface header" title="Direct link to Step 4: Write the interface header" translate=no>​</a></h2>
<p>Create <code>src/calc_ui_cpp_interface.h</code>:</p>
<div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>ifndef</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property expression" style=color:#36acaa>CALC_UI_CPP_INTERFACE_H</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>define</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property macro-name" style=color:#36acaa>CALC_UI_CPP_INTERFACE_H</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>&lt;QObject></span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>&lt;QString></span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"interface.h"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token class-name">CalcUiCppInterface</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token base-clause keyword" style=color:#00009f>public</span><span class="token base-clause"> </span><span class="token base-clause class-name">PluginInterface</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>public</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>virtual</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>~</span><span class="token function" style=color:#d73a49>CalcUiCppInterface</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>default</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>define</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property macro-name" style=color:#36acaa>CalcUiCppInterface_iid</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"org.logos.CalcUiCppInterface"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>Q_DECLARE_INTERFACE</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">CalcUiCppInterface</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> CalcUiCppInterface_iid</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>endif</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property comment" style=color:#999988;font-style:italic>// CALC_UI_CPP_INTERFACE_H</span><br/></div></code></pre></div></div>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-5-configure-the-cmake-build>Step 5: Configure the CMake build<a href=#step-5-configure-the-cmake-build class=hash-link aria-label="Direct link to Step 5: Configure the CMake build" title="Direct link to Step 5: Configure the CMake build" translate=no>​</a></h2>
<p>Create <code>CMakeLists.txt</code>:</p>
<div class="language-cmake codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cmake codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">cmake_minimum_required(VERSION 3.14)</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">project(CalcUiCppPlugin LANGUAGES CXX)</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">if(DEFINED ENV{LOGOS_MODULE_BUILDER_ROOT})</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> include($ENV{LOGOS_MODULE_BUILDER_ROOT}/cmake/LogosModule.cmake)</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">else()</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> message(FATAL_ERROR "LogosModule.cmake not found. Set LOGOS_MODULE_BUILDER_ROOT.")</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">endif()</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">logos_module(</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> NAME calc_ui_cpp</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> REP_FILE src/calc_ui_cpp.rep</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> SOURCES</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> src/calc_ui_cpp_interface.h</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> src/calc_ui_cpp_plugin.h</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> src/calc_ui_cpp_plugin.cpp</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">)</span><br/></div></code></pre></div></div>
<p><code>REP_FILE</code> tells <code>logos_module()</code> to run <code>repc</code> to generate source/replica headers, generate <code>CalcUiCppViewPluginBase</code>, and build a separate <code>calc_ui_cpp_replica_factory</code> shared library.</p>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-6-write-the-c-backend-plugin>Step 6: Write the C++ backend plugin<a href=#step-6-write-the-c-backend-plugin class=hash-link aria-label="Direct link to Step 6: Write the C++ backend plugin" title="Direct link to Step 6: Write the C++ backend plugin" translate=no>​</a></h2>
<p>The backend plugin inherits three base classes:</p>
<ul>
<li class=""><code>CalcUiCppSimpleSource</code> — generated from <code>.rep</code>, provides the typed source for Qt Remote Objects.</li>
<li class=""><code>CalcUiCppInterface</code> — standard Logos plugin interface (<code>name()</code>, <code>version()</code>).</li>
<li class=""><code>CalcUiCppViewPluginBase</code> — generated, provides <code>setBackend()</code> and <code>enableRemoting()</code>.</li>
</ul>
<ol>
<li class="">
<p>Create <code>src/calc_ui_cpp_plugin.h</code>:</p>
<div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>ifndef</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property expression" style=color:#36acaa>CALC_UI_CPP_PLUGIN_H</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>define</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property macro-name" style=color:#36acaa>CALC_UI_CPP_PLUGIN_H</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>&lt;QString></span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>&lt;QVariantList></span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"calc_ui_cpp_interface.h"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"LogosViewPluginBase.h"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"rep_calc_ui_cpp_source.h"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token class-name">LogosAPI</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token class-name">LogosModules</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token class-name">CalcUiCppPlugin</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token base-clause keyword" style=color:#00009f>public</span><span class="token base-clause"> </span><span class="token base-clause class-name">CalcUiCppSimpleSource</span><span class="token base-clause punctuation" style=color:#393A34>,</span><span class="token base-clause"></span><br/></div><div class=token-line style=color:#393A34><span class="token base-clause"> </span><span class="token base-clause keyword" style=color:#00009f>public</span><span class="token base-clause"> </span><span class="token base-clause class-name">CalcUiCppInterface</span><span class="token base-clause punctuation" style=color:#393A34>,</span><span class="token base-clause"></span><br/></div><div class=token-line style=color:#393A34><span class="token base-clause"> </span><span class="token base-clause keyword" style=color:#00009f>public</span><span class="token base-clause"> </span><span class="token base-clause class-name">CalcUiCppViewPluginBase</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Q_OBJECT</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>Q_PLUGIN_METADATA</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">IID CalcUiCppInterface_iid FILE </span><span class="token string" style=color:#e3116c>"metadata.json"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>Q_INTERFACES</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">CalcUiCppInterface</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>public</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>explicit</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>CalcUiCppPlugin</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">QObject</span><span class="token operator" style=color:#393A34>*</span><span class="token plain"> parent </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>nullptr</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token operator" style=color:#393A34>~</span><span class="token function" style=color:#d73a49>CalcUiCppPlugin</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>override</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> QString </span><span class="token function" style=color:#d73a49>name</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>const</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>override</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"calc_ui_cpp"</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> QString </span><span class="token function" style=color:#d73a49>version</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>const</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>override</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"1.0.0"</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Q_INVOKABLE </span><span class="token keyword" style=color:#00009f>void</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>initLogos</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">LogosAPI</span><span class="token operator" style=color:#393A34>*</span><span class="token plain"> api</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Slots from calc_ui_cpp.rep — return values directly. The QML replica</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// receives QRemoteObjectPendingReply; use logos.watch() in QML to get the value.</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>add</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> a</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> b</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>override</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>multiply</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> a</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> b</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>override</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>factorial</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> n</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>override</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>fibonacci</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> n</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>override</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> QString </span><span class="token function" style=color:#d73a49>libVersion</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>override</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">signals</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>void</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>eventResponse</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>const</span><span class="token plain"> QString</span><span class="token operator" style=color:#393A34>&</span><span class="token plain"> eventName</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>const</span><span class="token plain"> QVariantList</span><span class="token operator" style=color:#393A34>&</span><span class="token plain"> args</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>private</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> LogosAPI</span><span class="token operator" style=color:#393A34>*</span><span class="token plain"> m_logosAPI </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>nullptr</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> LogosModules</span><span class="token operator" style=color:#393A34>*</span><span class="token plain"> m_logos </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>nullptr</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>endif</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property comment" style=color:#999988;font-style:italic>// CALC_UI_CPP_PLUGIN_H</span><br/></div></code></pre></div></div>
<div class="theme-admonition theme-admonition-info admonition_xJq3 alert alert--info"><div class=admonitionHeading_Gvgb><span class=admonitionIcon_Rf37><svg viewBox="0 0 14 16"><path fill-rule=evenodd d="M7 2.3c3.14 0 5.7 2.56 5.7 5.7s-2.56 5.7-5.7 5.7A5.71 5.71 0 0 1 1.3 8c0-3.14 2.56-5.7 5.7-5.7zM7 1C3.14 1 0 4.14 0 8s3.14 7 7 7 7-3.14 7-7-3.14-7-7-7zm1 3H6v5h2V4zm0 6H6v2h2v-2z"/></svg></span>info</div><div class=admonitionContent_BuS1><p>If the interface filename or IID symbol here doesn't match the names in <code>src/calc_ui_cpp_interface.h</code>, you will get build errors or plugin-load failures at runtime.</div></div>
</li>
<li class="">
<p>Create <code>src/calc_ui_cpp_plugin.cpp</code>:</p>
<div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"calc_ui_cpp_plugin.h"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"logos_api.h"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"logos_sdk.h"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token class-name">CalcUiCppPlugin</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>CalcUiCppPlugin</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">QObject</span><span class="token operator" style=color:#393A34>*</span><span class="token plain"> parent</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>CalcUiCppSimpleSource</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">parent</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token class-name">CalcUiCppPlugin</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token operator" style=color:#393A34>~</span><span class="token function" style=color:#d73a49>CalcUiCppPlugin</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>delete</span><span class="token plain"> m_logos</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>void</span><span class="token plain"> </span><span class="token class-name">CalcUiCppPlugin</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>initLogos</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">LogosAPI</span><span class="token operator" style=color:#393A34>*</span><span class="token plain"> api</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>if</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">m_logos</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> m_logosAPI </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> api</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> m_logos </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>new</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>LogosModules</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">api</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Register this object as the Remote Objects source so the QML replica</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// can see its properties and call its slots.</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>setBackend</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>this</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token class-name">CalcUiCppPlugin</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>add</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> a</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> b</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token plain"> m_logos</span><span class="token operator" style=color:#393A34>-></span><span class="token plain">calc_module</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>add</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">a</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> b</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token class-name">CalcUiCppPlugin</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>multiply</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> a</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> b</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token plain"> m_logos</span><span class="token operator" style=color:#393A34>-></span><span class="token plain">calc_module</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>multiply</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">a</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> b</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token class-name">CalcUiCppPlugin</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>factorial</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> n</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token plain"> m_logos</span><span class="token operator" style=color:#393A34>-></span><span class="token plain">calc_module</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>factorial</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">n</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token class-name">CalcUiCppPlugin</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>fibonacci</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> n</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token plain"> m_logos</span><span class="token operator" style=color:#393A34>-></span><span class="token plain">calc_module</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>fibonacci</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">n</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">QString </span><span class="token class-name">CalcUiCppPlugin</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>libVersion</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token plain"> m_logos</span><span class="token operator" style=color:#393A34>-></span><span class="token plain">calc_module</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>libVersion</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><br/></div></code></pre></div></div>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-7-write-the-qml-view>Step 7: Write the QML view<a href=#step-7-write-the-qml-view class=hash-link aria-label="Direct link to Step 7: Write the QML view" title="Direct link to Step 7: Write the QML view" translate=no>​</a></h2>
<ol>
<li class="">
<p>Create <code>src/qml/Main.qml</code>:</p>
<div class="language-qml codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-qml codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">import QtQuick</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">import QtQuick.Controls</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">import QtQuick.Layouts</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">Item {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> id: root</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> property string result: ""</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> property string errorText: ""</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> // Typed replica of the backend running in ui-host (generated from calc_ui_cpp.rep).</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> readonly property var backend: logos.module("calc_ui_cpp")</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> // The ui-host backend connects asynchronously, so the replica isn't</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> // immediately usable. Track readiness reactively: isViewModuleReady()</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> // is a Q_INVOKABLE (not a property), so we re-check it on the</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> // onViewModuleReadyChanged signal and once at startup — never via a</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> // plain property binding, which would not re-evaluate.</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> property bool ready: false</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Connections {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> target: logos</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> function onViewModuleReadyChanged(moduleName, isReady) {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> if (moduleName === "calc_ui_cpp")</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> root.ready = isReady && root.backend !== null</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Component.onCompleted: {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> root.ready = root.backend !== null && logos.isViewModuleReady("calc_ui_cpp")</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> // logos.watch() delivers the result of a replica slot call via callbacks.</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> function callCalc(method, args) {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> if (!root.ready) {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> root.errorText = "Backend not ready"</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> return</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> root.errorText = ""</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> root.result = "..."</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> logos.watch(backend[method].apply(backend, args),</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> function(value) { root.result = String(value) },</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> function(error) { root.errorText = String(error) }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> )</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> ColumnLayout {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> anchors.fill: parent</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> anchors.margins: 24</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> spacing: 16</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Text {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> text: "Logos Calculator (C++ backend)"</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> font.pixelSize: 20</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> color: "#ffffff"</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Layout.alignment: Qt.AlignHCenter</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> // Reactive backend-connection indicator.</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Text {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> text: root.ready ? "Connected" : "Connecting to backend..."</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> color: root.ready ? "#56d364" : "#f0883e"</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> font.pixelSize: 12</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Layout.alignment: Qt.AlignHCenter</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> RowLayout {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> spacing: 12</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Layout.fillWidth: true</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> TextField { id: inputA; placeholderText: "a"; Layout.preferredWidth: 80; validator: IntValidator {} }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> TextField { id: inputB; placeholderText: "b"; Layout.preferredWidth: 80; validator: IntValidator {} }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Button {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> text: "Add"; enabled: root.ready</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> onClicked: root.callCalc("add", [parseInt(inputA.text) || 0, parseInt(inputB.text) || 0])</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Button {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> text: "Multiply"; enabled: root.ready</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> onClicked: root.callCalc("multiply", [parseInt(inputA.text) || 0, parseInt(inputB.text) || 0])</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> RowLayout {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> spacing: 12</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Layout.fillWidth: true</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> TextField { id: inputN; placeholderText: "n"; Layout.preferredWidth: 80; validator: IntValidator { bottom: 0 } }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Button { text: "Factorial"; enabled: root.ready; onClicked: root.callCalc("factorial", [parseInt(inputN.text) || 0]) }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Button { text: "Fibonacci"; enabled: root.ready; onClicked: root.callCalc("fibonacci", [parseInt(inputN.text) || 0]) }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Button { text: "libcalc version"; enabled: root.ready; onClicked: root.callCalc("libVersion", []) }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Rectangle {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Layout.fillWidth: true</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> height: 56</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> color: root.errorText.length > 0 ? "#3d1a1a" : "#1a2d1a"</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> radius: 8</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Text {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> anchors.centerIn: parent</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> text: root.errorText.length > 0 ? root.errorText</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> : (root.result.length > 0 ? root.result : "Enter values and press a button")</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> color: root.errorText.length > 0 ? "#f85149" : "#56d364"</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> font.pixelSize: 15</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> Item { Layout.fillHeight: true }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">}</span><br/></div></code></pre></div></div>
<p>Key patterns:</p>
<ul>
<li class=""><code>logos.module("calc_ui_cpp")</code> — gets the typed replica, with auto-synced properties.</li>
<li class=""><code>logos.watch(backend.add(1, 2), ...)</code> — delivers a <code>SLOT</code> return value as a JS Promise.</li>
<li class="">The <code>logos</code> object is injected by the host at runtime — no <code>QtRemoteObjects</code> import is needed.</li>
</ul>
</li>
</ol>
<h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-75-use-the-logos-design-system-in-your-qml-optional>Step 7.5: Use the Logos Design System in your QML (Optional)<a href=#step-75-use-the-logos-design-system-in-your-qml-optional class=hash-link aria-label="Direct link to Step 7.5: Use the Logos Design System in your QML (Optional)" title="Direct link to Step 7.5: Use the Logos Design System in your QML (Optional)" translate=no>​</a></h3>
<p>The QML view runs inside the <a href=https://github.com/logos-co/logos-standalone-app target=_blank rel="noopener noreferrer" class=""><code>logos-standalone-app</code></a> host app, which already has <a href=https://github.com/logos-co/logos-design-system target=_blank rel="noopener noreferrer" class=""><code>logos-design-system</code></a> on its import path. Use its themed components directly to automatically give your module a polished, consistent look.</p>
<ol>
<li class="">
<p>In <code>src/qml/Main.qml</code>, add the necessary imports and replace raw <code>Button</code> and <code>TextField</code> elements with design system equivalents:</p>
<div class="language-qml codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-qml codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">import Logos.Theme</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">import Logos.Controls</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">import Logos.Icons // optional shared icon assets</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">...</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">// Instead of Button:</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">LogosButton {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> text: qsTr("Add")</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> onClicked: root.callCalc("add", [parseInt(inputA.text) || 0,</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> parseInt(inputB.text) || 0])</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">}</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">...</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">// Instead of TextField:</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">LogosTextField {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> id: inputA</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> placeholderText: qsTr("a")</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">}</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">...</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">// Use theme colors instead of hardcoded hex values:</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">Rectangle {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> color: Theme.palette.backgroundSecondary</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> radius: Theme.spacing.radiusSmall</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> LogosText { text: qsTr("Result"); color: Theme.palette.text }</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">}</span><br/></div></code></pre></div></div>
</li>
<li class="">
<p>Explore available components by running the design system storybook in the logos-design-system repo:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">git clone https://github.com/logos-co/logos-design-system.git</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">cd logos-design-system && nix run</span><br/></div></code></pre></div></div>
<p>The sidebar splits components into:</p>
<ul>
<li class=""><strong>Controls</strong> — designed per Figma, production-ready (<code>LogosButton</code>, <code>LogosBadge</code>, <code>LogosCheckbox</code>, <code>LogosComboBox</code>, <code>LogosIconButton</code>, <code>LogosPaginator</code>, <code>LogosSearchBar</code>, <code>LogosTabBar</code>, <code>LogosTable</code>, <code>LogosText</code>, <code>LogosTextField</code>, <code>LogosToolTip</code>, …).</li>
<li class=""><strong>Controls (not designed)</strong> — placeholders with stable APIs but unstyled visuals (<code>LogosDialog</code>, <code>LogosDrawer</code>, <code>LogosScrollView</code>, <code>LogosSpinner</code>, <code>LogosTextArea</code>, <code>LogosSwitch</code>, …). You can ship with them; they'll get the polished look applied later without you having to change your QML.</li>
</ul>
<p><strong>Theme tokens</strong> (use these instead of hex literals or manual font sizes):</p>
<ul>
<li class=""><code>Theme.palette.-</code> — <code>background</code>, <code>backgroundSecondary</code>, <code>surface</code>, <code>text</code>, <code>textSecondary</code>, <code>border</code>, <code>primary</code>, <code>success</code>, <code>warning</code>, <code>error</code>, <code>info</code>, <code>hover</code>, <code>pressed</code>, …</li>
<li class=""><code>Theme.spacing.*</code> — <code>tiny</code>, <code>small</code>, <code>medium</code>, <code>large</code>, <code>xlarge</code>, <code>xxlarge</code>, <code>radiusSmall</code>, <code>radiusMedium</code>, <code>radiusLarge</code></li>
<li class=""><code>Theme.typography.*</code> — <code>pageTitleText</code> (36), <code>titleText</code> (30), <code>panelTitleText</code> (24), <code>subtitleText</code> (16), <code>primaryText</code> (14), <code>secondaryText</code> (12); <code>weightRegular</code> / <code>weightMedium</code> / <code>weightBold</code>; <code>publicSans</code></li>
<li class=""><code>Logos.Icons.LogosIcons.*</code> — <code>arrowLeft</code>, <code>arrowRight</code>, <code>refresh</code>, <code>install</code>, <code>trash</code>, <code>more</code>, <code>search</code>, …</li>
</ul>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-8-configure-the-nix-flake>Step 8: Configure the Nix flake<a href=#step-8-configure-the-nix-flake class=hash-link aria-label="Direct link to Step 8: Configure the Nix flake" title="Direct link to Step 8: Configure the Nix flake" translate=no>​</a></h2>
<p>The template already wires everything up. Update the description and point <code>calc_module</code> at your dependency.</p>
<ol>
<li class="">
<p>Replace <code>flake.nix</code> with the following:</p>
<div class="language-nix codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-nix codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">{</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> description = "Calculator C++ UI plugin for Logos - QML view with process-isolated backend for calc_module";</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> inputs = {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> logos-module-builder.url = "github:logos-co/logos-module-builder/0.2.0";</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> # Keep this placeholder as is - it gets locked to your real path in the next step.</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> calc_module.url = "path:/path/to/your/calc_module";</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> };</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> outputs = inputs@{ logos-module-builder, calc_module, ... }:</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> logos-module-builder.lib.mkLogosQmlModule {</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> src = ./.;</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> configFile = ./metadata.json;</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> flakeInputs = inputs;</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> };</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">}</span><br/></div></code></pre></div></div>
<p>To point at a published repo instead of a local path, change the <code>calc_module.url</code> input to a <code>github:</code> URL, for example <code>calc_module.url = "github:&lt;your-org>/&lt;your-calc-module>";</code>.</p>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-9-build-and-run-the-module>Step 9: Build and run the module<a href=#step-9-build-and-run-the-module class=hash-link aria-label="Direct link to Step 9: Build and run the module" title="Direct link to Step 9: Build and run the module" translate=no>​</a></h2>
<p>Before building, confirm the <code>calc_module</code> shared library is present from <a class="" href=/core/build-modules/wrap-a-c-library-as-a-logos-core-module>Part 1</a>.</p>
<ol>
<li class="">
<p>Confirm the shared library exists:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain"># Linux</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">ls ../logos-calc-module/lib/libcalc.so</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"># macOS</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">ls ../logos-calc-module/lib/libcalc.dylib</span><br/></div></code></pre></div></div>
<p>If the file is missing, build it first:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">cd ../logos-calc-module/lib</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">gcc -shared -fPIC -o libcalc.so libcalc.c # Linux</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"># gcc -shared -fPIC -o libcalc.dylib libcalc.c # macOS</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">cd ../../logos-calc-ui-cpp</span><br/></div></code></pre></div></div>
</li>
<li class="">
<p>Stage all files, then lock <code>calc_module</code> to your local Part 1 checkout. The <code>--override-input</code> flag resolves <code>../logos-calc-module</code> to an absolute path and records it in <code>flake.lock</code>:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">git add -A</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">nix flake update --override-input calc_module path:../logos-calc-module</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">git add flake.lock</span><br/></div></code></pre></div></div>
</li>
<li class="">
<p>Build and run the app. After the lock is in place, no override flag is needed on subsequent commands:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">nix run</span><br/></div></code></pre></div></div>
</li>
<li class="">
<p>Confirm the view loads with all controls visible, then click <strong>Add</strong> with values in the input fields to test it out:</p>
<p><img decoding=async loading=lazy alt="Operation buttons visible" src=/assets/images/calc-cpp-buttons-78885e103cdbbb8e471c0fbc6fbfdc01.png width=1024 height=768 class=img_ev3q /></p>
<p><img decoding=async loading=lazy alt="Result of 3 + 5 shows 8" src=/assets/images/calc-cpp-result-c33b1cae801fad3be492d3ad9b1a829d.png width=1024 height=768 class=img_ev3q /></p>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-10-update-view-with-live-reloading-optional>Step 10: Update view with live reloading (Optional)<a href=#step-10-update-view-with-live-reloading-optional class=hash-link aria-label="Direct link to Step 10: Update view with live reloading (Optional)" title="Direct link to Step 10: Update view with live reloading (Optional)" translate=no>​</a></h2>
<p>To enable live updates to the UI, set <code>DEV_QML_PATH</code> to the directory that contains your view entry's basename. This tutorial sets <code>"view": "qml/Main.qml"</code> in <code>metadata.json</code>, so the directory must contain <code>Main.qml</code> (here: <code>src/qml/</code>).</p>
<ol>
<li class="">
<p>Run with <code>DEV_QML_PATH</code> set so that QML is loaded from your source tree at runtime:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">DEV_QML_PATH=$PWD/src/qml nix run .</span><br/></div></code></pre></div></div>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=step-11-add-ui-integration-tests-optional>Step 11: Add UI integration tests (Optional)<a href=#step-11-add-ui-integration-tests-optional class=hash-link aria-label="Direct link to Step 11: Add UI integration tests (Optional)" title="Direct link to Step 11: Add UI integration tests (Optional)" translate=no>​</a></h2>
<p>Add automated UI tests using the <a href=https://github.com/logos-co/logos-qt-mcp target=_blank rel="noopener noreferrer" class="">logos-qt-mcp</a> test framework.</p>
<ol>
<li class="">
<p>Create <code>tests/ui-tests.mjs</code>:</p>
<div class="language-javascript codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-javascript codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token keyword module" style=color:#00009f>import</span><span class="token plain"> </span><span class="token imports punctuation" style=color:#393A34>{</span><span class="token imports"> resolve </span><span class="token imports punctuation" style=color:#393A34>}</span><span class="token plain"> </span><span class="token keyword module" style=color:#00009f>from</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"node:path"</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// CI sets LOGOS_QT_MCP automatically; for interactive use: nix build .#test-framework -o result-mcp</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>const</span><span class="token plain"> root </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> process</span><span class="token punctuation" style=color:#393A34>.</span><span class="token property-access">env</span><span class="token punctuation" style=color:#393A34>.</span><span class="token constant" style=color:#36acaa>LOGOS_QT_MCP</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>||</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>new</span><span class="token plain"> </span><span class="token class-name">URL</span><span class="token punctuation" style=color:#393A34>(</span><span class="token string" style=color:#e3116c>"../result-mcp"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token keyword module" style=color:#00009f>import</span><span class="token punctuation" style=color:#393A34>.</span><span class="token property-access">meta</span><span class="token punctuation" style=color:#393A34>.</span><span class="token property-access">url</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token property-access">pathname</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>const</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> test</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> run </span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword control-flow" style=color:#00009f>await</span><span class="token plain"> </span><span class="token keyword module" style=color:#00009f>import</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>resolve</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">root</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"test-framework/framework.mjs"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>test</span><span class="token punctuation" style=color:#393A34>(</span><span class="token string" style=color:#e3116c>"calc_ui_cpp: loads and shows title"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>async</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>(</span><span class="token parameter">app</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token arrow operator" style=color:#393A34>=></span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword control-flow" style=color:#00009f>await</span><span class="token plain"> app</span><span class="token punctuation" style=color:#393A34>.</span><span class="token method function property-access" style=color:#d73a49>waitFor</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>async</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token arrow operator" style=color:#393A34>=></span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword control-flow" style=color:#00009f>await</span><span class="token plain"> app</span><span class="token punctuation" style=color:#393A34>.</span><span class="token method function property-access" style=color:#d73a49>expectTexts</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>[</span><span class="token string" style=color:#e3116c>"Logos Calculator (C++ backend)"</span><span class="token punctuation" style=color:#393A34>]</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"> </span><span class="token literal-property property" style=color:#36acaa>timeout</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>15000</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token literal-property property" style=color:#36acaa>interval</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>500</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token literal-property property" style=color:#36acaa>description</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"UI to load"</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>test</span><span class="token punctuation" style=color:#393A34>(</span><span class="token string" style=color:#e3116c>"calc_ui_cpp: operation buttons visible"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>async</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>(</span><span class="token parameter">app</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token arrow operator" style=color:#393A34>=></span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword control-flow" style=color:#00009f>await</span><span class="token plain"> app</span><span class="token punctuation" style=color:#393A34>.</span><span class="token method function property-access" style=color:#d73a49>expectTexts</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>[</span><span class="token string" style=color:#e3116c>"Add"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Multiply"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Factorial"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Fibonacci"</span><span class="token punctuation" style=color:#393A34>]</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>run</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div>
</li>
<li class="">
<p>Stage the test file and run the hermetic CI test:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">git add tests/</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">nix build .#integration-test -L</span><br/></div></code></pre></div></div>
<p>The <code>integration-test</code> output launches <code>logos-standalone-app</code> with <code>QT_QPA_PLATFORM=offscreen</code> (no display needed), connects to the QML inspector, and runs all <code>.mjs</code> files in <code>tests/</code>.</p>
</li>
<li class="">
<p>To run tests interactively against an already-running app, build the test framework and run the app and tests in separate terminals:</p>
<div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-bash codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">nix build .#test-framework -o result-mcp</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">nix run . # terminal 1 — app with inspector on :3768</span><br/></div><div class=token-line style=color:#393A34><span class="token plain">node tests/ui-tests.mjs # terminal 2</span><br/></div></code></pre></div></div>
</li>
</ol>
<h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=troubleshooting-the-c-ui-module-build>Troubleshooting the C++ UI module build<a href=#troubleshooting-the-c-ui-module-build class=hash-link aria-label="Direct link to Troubleshooting the C++ UI module build" title="Direct link to Troubleshooting the C++ UI module build" translate=no>​</a></h2>
<h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=the-plugin-fails-to-load-at-runtime-with-no-clear-error>The plugin fails to load at runtime with no clear error<a href=#the-plugin-fails-to-load-at-runtime-with-no-clear-error class=hash-link aria-label="Direct link to The plugin fails to load at runtime with no clear error" title="Direct link to The plugin fails to load at runtime with no clear error" translate=no>​</a></h3>
<p>Confirm the <code>Q_PLUGIN_METADATA</code> IID and <code>Q_DECLARE_INTERFACE</code> macro in <code>calc_ui_cpp_interface.h</code> both use <code>CalcUiCppInterface_iid</code>. A mismatch causes silent load failures.</p>
<h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=linker-errors-during-nix-build>Linker errors during <code>nix build</code><a href=#linker-errors-during-nix-build class=hash-link aria-label="Direct link to linker-errors-during-nix-build" title="Direct link to linker-errors-during-nix-build" translate=no>​</a></h3>
<p>Confirm <code>../logos-calc-module/lib/libcalc.so</code> for Linux (or <code>.dylib</code> on macOS) exists and that <code>flake.lock</code> was updated with <code>--override-input calc_module path:../logos-calc-module</code>. A stale or placeholder lock file is the most common cause.</p>
<h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=dev_qml_path-does-not-seem-to-take-effect><code>DEV_QML_PATH</code> does not seem to take effect<a href=#dev_qml_path-does-not-seem-to-take-effect class=hash-link aria-label="Direct link to dev_qml_path-does-not-seem-to-take-effect" title="Direct link to dev_qml_path-does-not-seem-to-take-effect" translate=no>​</a></h3>
<p>Confirm the path points at the directory containing <code>Main.qml</code> directly — not a parent directory. The host looks for the basename from <code>"view"</code> in <code>metadata.json</code> inside the directory you provide.</div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="row margin-top--sm theme-doc-footer-edit-meta-row"><div class="col noPrint_WFHX"><a href=https://github.com/logos-co/logos-docs/tree/main/docs/core/build-modules/build-a-logos-cpp-ui-module.md target=_blank rel="noopener noreferrer" class=theme-edit-this-page><svg fill=currentColor height=20 width=20 viewBox="0 0 40 40" class=iconEdit_Z9Sw aria-hidden=true><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"/></g></svg>Edit this page</a></div><div class="col lastUpdated_JAkA"></div></div></footer></article><nav class="docusaurus-mt-lg pagination-nav" aria-label="Docs pages"><a class="pagination-nav__link pagination-nav__link--prev" href=/core/build-modules/wrap-a-c-library-as-a-logos-core-module><div class=pagination-nav__sublabel>Previous</div><div class=pagination-nav__label>Wrap a C library as a Logos module</div></a><a class="pagination-nav__link pagination-nav__link--next" href=/core/build-modules/install-and-load-a-module-in-logos-basecamp><div class=pagination-nav__sublabel>Next</div><div class=pagination-nav__label>Install and load a module in Logos Basecamp</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href=#what-to-expect class="table-of-contents__link toc-highlight">What to expect</a><li><a href=#step-1-scaffold-the-project class="table-of-contents__link toc-highlight">Step 1: Scaffold the project</a><li><a href=#step-2-configure-the-module-metadata class="table-of-contents__link toc-highlight">Step 2: Configure the module metadata</a><li><a href=#step-3-define-the-remote-interface class="table-of-contents__link toc-highlight">Step 3: Define the remote interface</a><li><a href=#step-4-write-the-interface-header class="table-of-contents__link toc-highlight">Step 4: Write the interface header</a><li><a href=#step-5-configure-the-cmake-build class="table-of-contents__link toc-highlight">Step 5: Configure the CMake build</a><li><a href=#step-6-write-the-c-backend-plugin class="table-of-contents__link toc-highlight">Step 6: Write the C++ backend plugin</a><li><a href=#step-7-write-the-qml-view class="table-of-contents__link toc-highlight">Step 7: Write the QML view</a><ul><li><a href=#step-75-use-the-logos-design-system-in-your-qml-optional class="table-of-contents__link toc-highlight">Step 7.5: Use the Logos Design System in your QML (Optional)</a></ul><li><a href=#step-8-configure-the-nix-flake class="table-of-contents__link toc-highlight">Step 8: Configure the Nix flake</a><li><a href=#step-9-build-and-run-the-module class="table-of-contents__link toc-highlight">Step 9: Build and run the module</a><li><a href=#step-10-update-view-with-live-reloading-optional class="table-of-contents__link toc-highlight">Step 10: Update view with live reloading (Optional)</a><li><a href=#step-11-add-ui-integration-tests-optional class="table-of-contents__link toc-highlight">Step 11: Add UI integration tests (Optional)</a><li><a href=#troubleshooting-the-c-ui-module-build class="table-of-contents__link toc-highlight">Troubleshooting the C++ UI module build</a><ul><li><a href=#the-plugin-fails-to-load-at-runtime-with-no-clear-error class="table-of-contents__link toc-highlight">The plugin fails to load at runtime with no clear error</a><li><a href=#linker-errors-during-nix-build class="table-of-contents__link toc-highlight">Linker errors during <code>nix build</code></a><li><a href=#dev_qml_path-does-not-seem-to-take-effect class="table-of-contents__link toc-highlight"><code>DEV_QML_PATH</code> does not seem to take effect</a></ul></ul></div></div></div></div></main></div></div></div><footer class="theme-layout-footer footer footer--dark"><div class="container container-fluid"><div class="row footer__links"><div class="theme-layout-footer-column col footer__col"><div class=footer__title>Docs</div><ul class="footer__items clean-list"><li class=footer__item><a class=footer__link-item href=/get-started/what-is-logos>Get started</a></ul></div><div class="theme-layout-footer-column col footer__col"><div class=footer__title>Community</div><ul class="footer__items clean-list"><li class=footer__item><a href=https://github.com/logos-co/logos-docs target=_blank rel="noopener noreferrer" class=footer__link-item>GitHub<svg width=13.5 height=13.5 aria-label="(opens in new tab)" class=iconExternalLink_nPIU><use href=#theme-svg-external-link /></svg></a></ul></div></div><div class="footer__bottom text--center"><div class=footer__copyright>Copyright © 2026 Logos. 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