Rate limit Viewport.refresh

src/Viewport.test.ts

@@ -1,6 +1,11 @@
 import { assert } from 'chai';
 import { Viewport } from './Viewport';
 
+class MockWindow {
+  // Disable refreshLoop in test
+  public requestAnimationFrame() { }
+}
+
 describe('Viewport', () => {
   var terminal;
   var viewportElement;
@@ -11,6 +16,7 @@ describe('Viewport', () => {
   const CHARACTER_HEIGHT = 10;
 
   beforeEach(() => {
+    (<any>global).window = new MockWindow();
     terminal = {
       lines: [],
       rows: 0,
@@ -73,10 +79,14 @@ describe('Viewport', () => {
       terminal.rows = 1;
       assert.equal(scrollAreaElement.style.height, 0 * CHARACTER_HEIGHT + 'px');
       viewport.syncScrollArea();
+      assert.ok(viewport.isRefreshQueued);
+      viewport.refresh();
       assert.equal(viewportElement.style.height, 1 * CHARACTER_HEIGHT + 'px');
       assert.equal(scrollAreaElement.style.height, 1 * CHARACTER_HEIGHT + 'px');
       terminal.lines.push('');
       viewport.syncScrollArea();
+      assert.ok(viewport.isRefreshQueued);
+      viewport.refresh();
       assert.equal(viewportElement.style.height, 1 * CHARACTER_HEIGHT + 'px');
       assert.equal(scrollAreaElement.style.height, 2 * CHARACTER_HEIGHT + 'px');
     });

src/Viewport.ts

@@ -12,6 +12,7 @@ export class Viewport {
   private currentRowHeight: number;
   private lastRecordedBufferLength: number;
   private lastRecordedViewportHeight: number;
+  private isRefreshQueued: boolean;
 
   /**
    * Creates a new Viewport.
@@ -29,12 +30,25 @@ export class Viewport {
     this.currentRowHeight = 0;
     this.lastRecordedBufferLength = 0;
     this.lastRecordedViewportHeight = 0;
+    this.isRefreshQueued = false;
 
     this.terminal.on('scroll', this.syncScrollArea.bind(this));
     this.terminal.on('resize', this.syncScrollArea.bind(this));
     this.viewportElement.addEventListener('scroll', this.onScroll.bind(this));
 
     this.syncScrollArea();
+    this.refreshLoop();
+  }
+
+  /**
+   * Queues a refresh to be done on next animation frame.
+   */
+  private refreshLoop(): void {
+    if (this.isRefreshQueued) {
+      this.refresh();
+      this.isRefreshQueued = false;
+    }
+    window.requestAnimationFrame(this.refreshLoop.bind(this));
   }
 
   /**
@@ -68,15 +82,15 @@ export class Viewport {
     if (this.lastRecordedBufferLength !== this.terminal.lines.length) {
       // If buffer height changed
       this.lastRecordedBufferLength = this.terminal.lines.length;
-      this.refresh();
+      this.isRefreshQueued = true;
     } else if (this.lastRecordedViewportHeight !== this.terminal.rows) {
       // If viewport height changed
-      this.refresh();
+      this.isRefreshQueued = true;
     } else {
       // If size has changed, refresh viewport
       var size = this.charMeasureElement.getBoundingClientRect();
       if (size.height !== this.currentRowHeight) {
-        this.refresh(size);
+        this.isRefreshQueued = true;
       }
     }