8c8944c10f
Summary: This is a long story. Awhile ago awesome Nick Lockwood (Hey Nick!) introduced a special optimization for ReactNative rendering layer called "inherited background color". He described this idea in D2811031: >>> Blending semitransparent pixels against their background is fairly a fairly expensive operation on mobile GPUs. To reduce blending, React Native has a system called "background color propagation", where the background color of parent views is automatically inherited by child views unless explicitly overridden. This means that translucent pixels can be blended directly against a known background color, avoiding the need to do this dynamically on the GPU. In practice, this is only useful for views that do their own drawing, which is basically just <Image/> and <Text/> components, and for image components it only really matters when the image has an alpha component. The automatic background propagation is a bit of a hack, and often does the wrong thing - for example if a view overflows its bounds, or if it overlaps a sibling, the background color will often be incorrect and need to be manually disabled. Because the only place that it provides a significant performance benefit is for text, this diff disables the behavior for everything except <Text/> nodes. It might still be useful for <Image/> nodes too, but looking through the examples in UIExplorer, the number of places where it does the wrong thing for images outnumbers the cases where it provides significant reduction in blending. However. I think it is time to remove it. Why? There are several reasons: * It drastically complicates rendering layer. DRASTICALLY. In many many unrelated places (try search for "backgroundColor"!); * This mechanism is totally non-conceptual to RN and it prevents us to implement some new possible render optimization that we plan to do; * This adopted only by two components now: Text and ART; * This is not a significant performance drain anymore; from iOS 6 even UILabel has clear background color by default. * I doubt that it even works now because `drawRect:` in Text component does not call super method. So, this diff just turns this feature off for Text. If all performance metrics are neutral, I will delete this mechanism. Peace. Reviewed By: sahrens Differential Revision: D6564199 fbshipit-source-id: 70524fdd955ca32bbf86d2d1ff5e73316b791219 |
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|---|---|---|
| .. | ||
| RNTester | ||
| RNTester-tvOS | ||
| RNTester.xcodeproj | ||
| RNTesterIntegrationTests | ||
| RNTesterLegacy.xcodeproj | ||
| RNTesterUnitTests | ||
| android/app | ||
| js | ||
| .eslintrc | ||
| README.md | ||
README.md
RNTester
The RNTester showcases React Native views and modules.
Running this app
Before running the app, make sure you ran:
git clone https://github.com/facebook/react-native.git
cd react-native
npm install
Running on iOS
Mac OS and Xcode are required.
- Open
RNTester/RNTester.xcodeprojin Xcode - Hit the Run button
See Running on device if you want to use a physical device.
Running on Android
You'll need to have all the prerequisites (SDK, NDK) for Building React Native installed.
Start an Android emulator (Genymotion is recommended).
cd react-native
./gradlew :RNTester:android:app:installDebug
./scripts/packager.sh
Note: Building for the first time can take a while.
Open the RNTester app in your emulator.
See Running on Device in case you want to use a physical device.
Running with Buck
Follow the same setup as running with gradle.
Install Buck from here.
Run the following commands from the react-native folder:
./gradlew :ReactAndroid:packageReactNdkLibsForBuck
buck fetch rntester
buck install -r rntester
./scripts/packager.sh
Note: The native libs are still built using gradle. Full build with buck is coming soon(tm).
Built from source
Building the app on both iOS and Android means building the React Native framework from source. This way you're running the latest native and JS code the way you see it in your clone of the github repo.
This is different from apps created using react-native init which have a dependency on a specific version of React Native JS and native code, declared in a package.json file (and build.gradle for Android apps).