Merge pull request #4131 from Tyriar/idleWarmup

Perform texture atlas warm up in an idle callback

Author: Tyriar

addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts

@@ -121,16 +121,20 @@ export class WebglCharAtlas implements IDisposable {
 
   public warmUp(): void {
     if (!this._didWarmUp) {
-      this._doWarmUp();
+      (typeof requestIdleCallback !== 'function' ? requestIdleCallback : setTimeout)(() => {
+        this._doWarmUp();
+      });
       this._didWarmUp = true;
     }
   }
 
   private _doWarmUp(): void {
     // Pre-fill with ASCII 33-126
     for (let i = 33; i < 126; i++) {
-      const rasterizedGlyph = this._drawToCache(i, DEFAULT_COLOR, DEFAULT_COLOR, DEFAULT_EXT);
-      this._cacheMap.set(i, DEFAULT_COLOR, DEFAULT_COLOR, DEFAULT_EXT, rasterizedGlyph);
+      if (!this._cacheMap.get(i, DEFAULT_COLOR, DEFAULT_COLOR, DEFAULT_EXT)) {
+        const rasterizedGlyph = this._drawToCache(i, DEFAULT_COLOR, DEFAULT_COLOR, DEFAULT_EXT);
+        this._cacheMap.set(i, DEFAULT_COLOR, DEFAULT_COLOR, DEFAULT_EXT, rasterizedGlyph);
+      }
     }
   }