From 5c4b75ce6a061f4b52fab52db18e86842fe5bb66 Mon Sep 17 00:00:00 2001
From: Anthony Laibe <anthony@laibe.cc>
Date: Mon, 30 Aug 2021 11:49:13 +0200
Subject: [PATCH] perf(@desktop/chat): Improve performance when big member list

Avoid computation when it is not needed for the suggestion filter

This is quite visible when the member list contains 1000s of members.
It is the case when you load historical message (1 month)
---
 .../Chat/ChatColumn/SuggestionFilter.qml      | 79 ++++++++++++-------
 1 file changed, 51 insertions(+), 28 deletions(-)

diff --git a/ui/app/AppLayouts/Chat/ChatColumn/SuggestionFilter.qml b/ui/app/AppLayouts/Chat/ChatColumn/SuggestionFilter.qml
index d933b23923..4c7f9b46b4 100644
--- a/ui/app/AppLayouts/Chat/ChatColumn/SuggestionFilter.qml
+++ b/ui/app/AppLayouts/Chat/ChatColumn/SuggestionFilter.qml
@@ -1,5 +1,6 @@
 import QtQuick 2.13
 
+
 Item {
     id: component
     property alias model: filterModel
@@ -24,53 +25,45 @@ Item {
     }
 
     function invalidateFilter() {
-        if (sourceModel === undefined)
-            return;
-
-        filterModel.clear();
+        filterModel.clear();     
 
         if (!isFilteringPropertyOk())
             return
 
-        var length = sourceModel.rowCount()
-        for (var i = 0; i < length; ++i) {
+        var filter = getFilter()
+        if (!isFilterReady(filter))
+            return
+
+        const all = shouldShowAll(filter)
+
+        for (var i = 0; i < sourceModel.rowCount(); ++i) {
             const publicKey = sourceModel.rowData(i, "publicKey");
-            var item = {
+            const item = {
                 alias: sourceModel.rowData(i, "alias"),
                 userName: sourceModel.rowData(i, "userName"),
                 publicKey: publicKey,
                 identicon: getProfileImage(publicKey, false, false) || sourceModel.rowData(i, "identicon"),
                 localName: sourceModel.rowData(i, "localName")
             }
-            if (isAcceptedItem(item)) {
+            if (all || isAcceptedItem(filter, item)) {
                 filterModel.append(item)
             }
         }
     }
 
-    function isAcceptedItem(item) {
-        let properties = this.property
-            .filter(p => !!item[p])
-
-        if (properties.length === 0 || this.filter.length === 0 || this.cursorPosition === 0) {
-            return false
+    function getFilter() {
+        if (this.filter.length === 0 || this.cursorPosition === 0) {
+            return
         }
 
-        let filter = chatsModel.plainText(this.filter)
-        // Prevents suggestions to show up at all
-        if (filter.indexOf("@") === -1)  {
-          return false
-        }
+        return chatsModel.plainText(this.filter)
+    }
 
-        let cursorAtEnd = this.cursorPosition === filter.length;
-        let hasAtBeforeCursor = filter.charAt(this.cursorPosition - 1) === "@" 
-        let hasWhiteSpaceBeforeAt = filter.charAt(this.cursorPosition - 2) === " " || filter.charAt(this.cursorPosition - 2) === "\n"
-        let hasWhiteSpaceAfterAt = filter.charAt(this.cursorPosition) === " "
-        let hasWhiteSpaceBeforeCursor = filter.charAt(this.cursorPosition - 1) === " "
-
-        if (filter.charAt(this.cursorPosition - 2) === "@" && hasWhiteSpaceBeforeCursor) {
-            return false
-        }
+    function shouldShowAll(filter) {
+        var cursorAtEnd = this.cursorPosition === filter.length;
+        var hasAtBeforeCursor = filter.charAt(this.cursorPosition - 1) === "@" 
+        var hasWhiteSpaceBeforeAt = filter.charAt(this.cursorPosition - 2) === " " || filter.charAt(this.cursorPosition - 2) === "\n"
+        var hasWhiteSpaceAfterAt = filter.charAt(this.cursorPosition) === " "
 
         if (filter === "@" ||
                 (hasAtBeforeCursor && hasWhiteSpaceBeforeAt && hasWhiteSpaceAfterAt) ||
@@ -80,6 +73,36 @@ Item {
             return true
         }
 
+        return false
+    }
+
+    function isFilterReady(filter) {
+        if (filter === undefined) {
+            return false
+        }
+
+        // Prevents suggestions to show up at all
+        if (filter.indexOf("@") === -1)  {
+          return false
+        }
+
+        let hasWhiteSpaceBeforeCursor = filter.charAt(this.cursorPosition - 1) === " "
+
+        if (filter.charAt(this.cursorPosition - 2) === "@" && hasWhiteSpaceBeforeCursor) {
+            return false
+        }
+
+        return true
+    }
+
+    function isAcceptedItem(filter, item) {
+        let properties = this.property
+            .filter(p => !!item[p])
+
+        if (properties.length === 0) {
+            return false
+        }
+        
         let filterWithoutAt = filter.substring(lastAtPosition + 1, this.cursorPosition)
         filterWithoutAt = filterWithoutAt.replace(/\*/g, "")
         component.formattedFilter = filterWithoutAt