Attempt to address colorization issue with flickering on Mac

Extension/CHANGELOG.md

@@ -1,6 +1,6 @@
 # C/C++ for Visual Studio Code Change Log
 
-## Version 0.24.0-insiders: June 13, 2019
+## Version 0.24.0-insiders: June 14, 2019
 ### New Features
 * Syntactic/lexical and semantic colorization [PR #3651](https://github.com/microsoft/vscode-cpptools/pull/3651) [Documentation](https://github.com/microsoft/vscode-cpptools/blob/master/Documentation/LanguageServer/colorization.md)
 * Add `Rescan Workspace` command. [microsoft/vscode-cpptools-api#11](https://github.com/microsoft/vscode-cpptools-api/issues/11)

Extension/src/LanguageServer/colorization.ts

@@ -443,10 +443,19 @@ export class ColorizationState {
     }
 
     private refreshInner(e: vscode.TextEditor): void {
-        // Clear inactive regions
-        if (this.inactiveDecoration) {
-            e.setDecorations(this.inactiveDecoration, []);
-        }
+
+        // The only way to un-apply decorators is to dispose them.
+        // If we dispose old decorators before applying new decorators, we see a flicker on Mac,
+        // likely due to a race with UI updates.  Here we set aside the existing decorators to be
+        // disposed of after the new decorators have been applied, so there is not a gap
+        // in which decorators are not applied.
+        let oldInactiveDecoration: vscode.TextEditorDecorationType = this.inactiveDecoration;
+        let oldDecorations: vscode.TextEditorDecorationType[] = this.decorations;
+        this.inactiveDecoration = null;
+        this.decorations =  new Array<vscode.TextEditorDecorationType>(TokenKind.Count);
+
+        this.createColorizationDecorations(e.document.languageId === "cpp");
+
         let settings: CppSettings = new CppSettings(this.uri);
         if (settings.enhancedColorization === "Enabled" && settings.intelliSenseEngine === "Default") {
             for (let i: number = 0; i < TokenKind.Count; i++) {
@@ -465,10 +474,26 @@ export class ColorizationState {
                 }
             }
         }
-        // Apply dimming last
+
+        // Normally, decorators are honored in the order in which they were created, not the 
+        // order in which they were applied.  Decorators with opacity appear to be handled
+        // differently, in that the opacity is applied to overlapping decorators even if
+        // created afterwards.
         if (settings.dimInactiveRegions && this.inactiveDecoration && this.inactiveRanges) {
             e.setDecorations(this.inactiveDecoration, this.inactiveRanges);
         }
+
+        // Dispose of the old decorators only after the new ones have been applied.
+        if (oldInactiveDecoration) {
+            oldInactiveDecoration.dispose();
+        }
+        if (oldDecorations) {
+            for (let i: number = 0; i < TokenKind.Count; i++) {
+                if (oldDecorations[i]) {
+                    oldDecorations[i].dispose();
+                }
+            }
+        }
     }
 
     public refresh(e: vscode.TextEditor): void {
@@ -647,13 +672,6 @@ export class ColorizationState {
             }
         }
         let f: () => void = async () => {
-            // Dispose of original decorators.
-            // Disposing and recreating is simpler than setting decorators to empty ranges in each editor showing this file
-            this.disposeColorizationDecorations();
-
-            let isCpp: boolean = util.isEditorFileCpp(uri);
-            this.createColorizationDecorations(isCpp);
-
             // Apply the decorations to all *visible* text editors
             let editors: vscode.TextEditor[] = vscode.window.visibleTextEditors.filter(e => e.document.uri.toString() === uri);
             for (let e of editors) {