Merge pull request #2388 from ShahzadUmair/Support-for-bubbling-scroll

Support for bubbling scroll events to parent(s)

src/Terminal.ts

@@ -1037,8 +1037,9 @@ export class Terminal extends Disposable implements ITerminal, IDisposable, IInp
     // the shell for example
     this.register(addDisposableDomListener(el, 'wheel', (ev: WheelEvent) => {
       if (this.mouseEvents) return;
-      this.viewport.onWheel(ev);
-      return this.cancel(ev);
+      if (!this.viewport.onWheel(ev)) {
+        return this.cancel(ev);
+      }
     }));
 
     this.register(addDisposableDomListener(el, 'touchstart', (ev: TouchEvent) => {
@@ -1049,8 +1050,9 @@ export class Terminal extends Disposable implements ITerminal, IDisposable, IInp
 
     this.register(addDisposableDomListener(el, 'touchmove', (ev: TouchEvent) => {
       if (this.mouseEvents) return;
-      this.viewport.onTouchMove(ev);
-      return this.cancel(ev);
+      if (!this.viewport.onTouchMove(ev)) {
+        return this.cancel(ev);
+      }
     }));
   }
 

src/TestUtils.test.ts

@@ -410,13 +410,13 @@ export class MockViewport implements IViewport {
   onThemeChange(colors: IColorSet): void {
     throw new Error('Method not implemented.');
   }
-  onWheel(ev: WheelEvent): void {
+  onWheel(ev: WheelEvent): boolean {
     throw new Error('Method not implemented.');
   }
   onTouchStart(ev: TouchEvent): void {
     throw new Error('Method not implemented.');
   }
-  onTouchMove(ev: TouchEvent): void {
+  onTouchMove(ev: TouchEvent): boolean {
     throw new Error('Method not implemented.');
   }
   syncScrollArea(): void { }

src/browser/Types.d.ts

@@ -37,9 +37,9 @@ export interface IViewport extends IDisposable {
   scrollBarWidth: number;
   syncScrollArea(): void;
   getLinesScrolled(ev: WheelEvent): number;
-  onWheel(ev: WheelEvent): void;
+  onWheel(ev: WheelEvent): boolean;
   onTouchStart(ev: TouchEvent): void;
-  onTouchMove(ev: TouchEvent): void;
+  onTouchMove(ev: TouchEvent): boolean;
   onThemeChange(colors: IColorSet): void;
 }
 

src/browser/Viewport.ts

@@ -152,20 +152,36 @@ export class Viewport extends Disposable implements IViewport {
     this._scrollLines(diff, true);
   }
 
+  /**
+   * Handles bubbling of scroll event in case the viewport has reached top or bottom
+   * @param ev The scroll event.
+   * @param amount The amount scrolled
+   */
+  private _bubbleScroll(ev: Event, amount: number): boolean {
+    const scrollPosFromTop = this._viewportElement.scrollTop + this._lastRecordedViewportHeight;
+    if ((amount < 0 && this._viewportElement.scrollTop !== 0) ||
+        (amount > 0 &&  scrollPosFromTop < this._lastRecordedBufferHeight)) {
+      if (ev.cancelable) {
+        ev.preventDefault();
+      }
+      return false;
+    }
+    return true;
+  }
+
   /**
    * Handles mouse wheel events by adjusting the viewport's scrollTop and delegating the actual
    * scrolling to `onScroll`, this event needs to be attached manually by the consumer of
    * `Viewport`.
    * @param ev The mouse wheel event.
    */
-  public onWheel(ev: WheelEvent): void {
+  public onWheel(ev: WheelEvent): boolean {
     const amount = this._getPixelsScrolled(ev);
     if (amount === 0) {
-      return;
+      return false;
     }
     this._viewportElement.scrollTop += amount;
-    // Prevent the page from scrolling when the terminal scrolls
-    ev.preventDefault();
+    return this._bubbleScroll(ev, amount);
   }
 
   private _getPixelsScrolled(ev: WheelEvent): number {
@@ -220,13 +236,13 @@ export class Viewport extends Disposable implements IViewport {
    * Handles the touchmove event, scrolling the viewport if the position shifted.
    * @param ev The touch event.
    */
-  public onTouchMove(ev: TouchEvent): void {
+  public onTouchMove(ev: TouchEvent): boolean {
     const deltaY = this._lastTouchY - ev.touches[0].pageY;
     this._lastTouchY = ev.touches[0].pageY;
     if (deltaY === 0) {
-      return;
+      return false;
     }
     this._viewportElement.scrollTop += deltaY;
-    ev.preventDefault();
+    return this._bubbleScroll(ev, deltaY);
   }
 }