Add smoothScroll to scrollLines

src/browser/Terminal.ts

@@ -21,7 +21,7 @@
  *   http://linux.die.net/man/7/urxvt
  */
 
-import { ICompositionHelper, ITerminal, IBrowser, CustomKeyEventHandler, IViewport, ILinkifier2, CharacterJoinerHandler, IBufferRange, IBufferElementProvider } from 'browser/Types';
+import { ICompositionHelper, ITerminal, IBrowser, CustomKeyEventHandler, IViewport, ILinkifier2, CharacterJoinerHandler, IBufferRange, IBufferElementProvider, ISmoothScrollProgressState } from 'browser/Types';
 import { IRenderer } from 'browser/renderer/shared/Types';
 import { CompositionHelper } from 'browser/input/CompositionHelper';
 import { Viewport } from 'browser/Viewport';
@@ -122,6 +122,13 @@ export class Terminal extends CoreTerminal implements ITerminal {
   private _compositionHelper: ICompositionHelper | undefined;
   private _accessibilityManager: AccessibilityManager | undefined;
 
+  private _smoothScrollProgressState: ISmoothScrollProgressState = {
+    startTime: 0,
+    origin: 0,
+    target: 0,
+    progress: 0
+  };
+
   private readonly _onCursorMove = this.register(new EventEmitter<void>());
   public readonly onCursorMove = this._onCursorMove.event;
   private readonly _onKey = this.register(new EventEmitter<{ key: string, domEvent: KeyboardEvent }>());
@@ -869,11 +876,76 @@ export class Terminal extends CoreTerminal implements ITerminal {
     }
   }
 
-  public scrollLines(disp: number, suppressScrollEvent?: boolean, source = ScrollSource.TERMINAL): void {
+  private _scrollLines(disp: number, suppressScrollEvent?: boolean, source = ScrollSource.TERMINAL): void {
     super.scrollLines(disp, suppressScrollEvent, source);
     this.refresh(0, this.rows - 1);
   }
 
+  public scrollLines(disp: number, suppressScrollEvent?: boolean, source = ScrollSource.TERMINAL): void {
+    if (source === ScrollSource.VIEWPORT) {
+      this._scrollLines(disp, suppressScrollEvent, source);
+    } else {
+      if (!this.optionsService.rawOptions.smoothScrollDuration) {
+        this._scrollLines(disp, suppressScrollEvent, source);
+      } else {
+        this._smoothScrollProgressState.startTime = Date.now();
+        if (this._smoothScrollPercent() < 1) {
+          this._smoothScrollProgressState.origin = 0;
+          this._smoothScrollProgressState.target = disp;
+          this._smoothScrollProgressState.progress = 0;
+          this._smoothScroll(suppressScrollEvent, source);
+        } else {
+          this._clearSmoothScrollState();
+        }
+      }
+    }
+  }
+
+  private _smoothScrollPercent(): number {
+    if (!this.optionsService.rawOptions.smoothScrollDuration || !this._smoothScrollProgressState.startTime) {
+      return 1;
+    }
+    return Math.max(Math.min((Date.now() - this._smoothScrollProgressState.startTime) / this.optionsService.rawOptions.smoothScrollDuration, 1), 0);
+  }
+
+  private _isSmoothScrollEnd(): boolean {
+    if (this._smoothScrollProgressState.target < 0) {
+      if (this._smoothScrollProgressState.progress > this._smoothScrollProgressState.target) {
+        return false;
+      }
+    } else if (this._smoothScrollProgressState.target > 0) {
+      if (this._smoothScrollProgressState.progress < this._smoothScrollProgressState.target) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  private _smoothScroll(suppressScrollEvent?: boolean, source = ScrollSource.TERMINAL): void {
+    if (this._smoothScrollProgressState.startTime === 0 || this._isSmoothScrollEnd()) {
+      return;
+    }
+
+    const percent = this._smoothScrollPercent();
+    const step = Math.round(percent * (this._smoothScrollProgressState.target - this._smoothScrollProgressState.origin)) - this._smoothScrollProgressState.progress;
+    this._smoothScrollProgressState.progress += step;
+    this._scrollLines(step, suppressScrollEvent, source);
+
+    if (this._isSmoothScrollEnd()) {
+      this._clearSmoothScrollState();
+      return;
+    }
+
+    this._coreBrowserService?.window.requestAnimationFrame(() => this._smoothScroll(suppressScrollEvent, source));
+  }
+
+  private _clearSmoothScrollState(): void {
+    this._smoothScrollProgressState.origin = 0;
+    this._smoothScrollProgressState.target = 0;
+    this._smoothScrollProgressState.progress = 0;
+    this._smoothScrollProgressState.startTime = 0;
+  }
+
   public paste(data: string): void {
     paste(data, this.textarea!, this.coreService);
   }