Do char atlas warmup via new IdleTaskQueue

src/common/IdleTaskQueue.ts

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) 2022 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+export class IdleTaskQueue {
+  private _tasks: Function[] = [];
+  private _idleCallback?: number;
+  private _maxTaskDuration: number;
+  private _i = 0;
+
+  constructor(targetFps: number = 240) {
+    this._maxTaskDuration = 1000 / targetFps;
+  }
+
+  public enqueue(task: Function): void {
+    this._tasks.push(task);
+    this._start();
+  }
+
+  private _start(): void {
+    if (!this._idleCallback) {
+      this._idleCallback = requestIdleCallback(() => this._process());
+    }
+  }
+
+  private _process(): void {
+    const start = performance.now();
+    this._idleCallback = undefined;
+    while (this._i < this._tasks.length) {
+      this._tasks[this._i++]();
+      if (performance.now() - start > this._maxTaskDuration) {
+        this._start();
+        return;
+      }
+    }
+    // Clear the queue
+    this._i = 0;
+    this._tasks.length = 0;
+  }
+}