From 523887d6c52267d6c41fb18454f86e0b84d4a55f Mon Sep 17 00:00:00 2001
From: Alexandre Poirot <poirot.alex@gmail.com>
Date: Mon, 27 Jun 2022 14:03:19 +0000
Subject: [PATCH] Bug 1775200 - [devtools] Avoid updating CodeMirror unless it
 is strictly necessary. r=bomsy

There is many props that are only relevant to the children components,
and we were calling expensive CodeMirror method on any prop change.

Differential Revision: https://phabricator.services.mozilla.com/D149853
---
 .../debugger/src/components/Editor/index.js   | 59 +++++++++++--------
 1 file changed, 33 insertions(+), 26 deletions(-)

diff --git a/devtools/client/debugger/src/components/Editor/index.js b/devtools/client/debugger/src/components/Editor/index.js
index 9b7f486c08ec9..d7afb2d846cd4 100644
--- a/devtools/client/debugger/src/components/Editor/index.js
+++ b/devtools/client/debugger/src/components/Editor/index.js
@@ -159,11 +159,33 @@ class Editor extends PureComponent {
       editor = this.setupEditor();
     }
 
-    startOperation();
-    this.setText(nextProps, editor);
-    this.setSize(nextProps, editor);
-    this.scrollToLocation(nextProps, editor);
-    endOperation();
+    const shouldUpdateText =
+      nextProps.selectedSource !== this.props.selectedSource ||
+      nextProps.selectedSourceTextContent !==
+        this.props.selectedSourceTextContent ||
+      nextProps.symbols !== this.props.symbols;
+
+    const shouldUpdateSize =
+      nextProps.startPanelSize !== this.props.startPanelSize ||
+      nextProps.endPanelSize !== this.props.endPanelSize;
+
+    const shouldScroll =
+      nextProps.selectedLocation &&
+      this.shouldScrollToLocation(nextProps, editor);
+
+    if (shouldUpdateText || shouldUpdateSize || shouldScroll) {
+      startOperation();
+      if (shouldUpdateText) {
+        this.setText(nextProps, editor);
+      }
+      if (shouldUpdateSize) {
+        editor.codeMirror.setSize();
+      }
+      if (shouldScroll) {
+        this.scrollToLocation(nextProps, editor);
+      }
+      endOperation();
+    }
 
     if (this.props.selectedSource != nextProps.selectedSource) {
       this.props.updateViewport();
@@ -555,30 +577,15 @@ class Editor extends PureComponent {
   scrollToLocation(nextProps, editor) {
     const { selectedLocation, selectedSource } = nextProps;
 
-    if (selectedLocation && this.shouldScrollToLocation(nextProps, editor)) {
-      let { line, column } = toEditorPosition(selectedLocation);
-
-      if (selectedSource && hasDocument(selectedSource.id)) {
-        const doc = getDocument(selectedSource.id);
-        const lineText = doc.getLine(line);
-        column = Math.max(column, getIndentation(lineText));
-      }
+    let { line, column } = toEditorPosition(selectedLocation);
 
-      scrollToColumn(editor.codeMirror, line, column);
-    }
-  }
-
-  setSize(nextProps, editor) {
-    if (!editor) {
-      return;
+    if (selectedSource && hasDocument(selectedSource.id)) {
+      const doc = getDocument(selectedSource.id);
+      const lineText = doc.getLine(line);
+      column = Math.max(column, getIndentation(lineText));
     }
 
-    if (
-      nextProps.startPanelSize !== this.props.startPanelSize ||
-      nextProps.endPanelSize !== this.props.endPanelSize
-    ) {
-      editor.codeMirror.setSize();
-    }
+    scrollToColumn(editor.codeMirror, line, column);
   }
 
   setText(props, editor) {