Move custom mouse event handler into MouseStateService

Don't need to keep it in CoreBrowserTerminal

src/common/TestUtils.test.ts

@@ -82,6 +82,8 @@ export class MockMouseStateService implements IMouseStateService {
   public consumeWheelEvent(ev: WheelEvent, cellHeight: number, dpr: number): number {
     return 1;
   }
+  public setCustomWheelEventHandler(customWheelEventHandler: ((event: WheelEvent) => boolean) | undefined): void { }
+  public allowCustomWheelEvent(ev: WheelEvent): boolean { return true; }
 }
 
 export class MockCharsetService implements ICharsetService {

src/common/services/MouseStateService.ts

@@ -175,6 +175,7 @@ export class MouseStateService extends Disposable implements IMouseStateService
   private _activeEncoding: string = '';
   private _lastEvent: ICoreMouseEvent | null = null;
   private _wheelPartialScroll: number = 0;
+  private _customWheelEventHandler: ((event: WheelEvent) => boolean) | undefined;
 
   private readonly _onProtocolChange = this._register(new Emitter<CoreMouseEventType>());
   public readonly onProtocolChange = this._onProtocolChange.event;
@@ -268,6 +269,14 @@ export class MouseStateService extends Disposable implements IMouseStateService
     return amount;
   }
 
+  public setCustomWheelEventHandler(customWheelEventHandler: ((event: WheelEvent) => boolean) | undefined): void {
+    this._customWheelEventHandler = customWheelEventHandler;
+  }
+
+  public allowCustomWheelEvent(ev: WheelEvent): boolean {
+    return this._customWheelEventHandler ? this._customWheelEventHandler(ev) !== false : true;
+  }
+
   private _applyScrollModifier(amount: number, ev: WheelEvent): number {
     // Multiply the scroll speed when the modifier key is pressed
     if (ev.altKey || ev.ctrlKey || ev.shiftKey) {

src/common/services/Services.ts

@@ -70,6 +70,16 @@ export interface IMouseStateService {
    * Process wheel event taking partial scroll into account.
    */
   consumeWheelEvent(ev: WheelEvent, cellHeight?: number, dpr?: number): number;
+
+  /**
+   * Sets a custom wheel event handler that can veto wheel processing.
+   */
+  setCustomWheelEventHandler(customWheelEventHandler: ((event: WheelEvent) => boolean) | undefined): void;
+
+  /**
+   * Checks whether a wheel event should be processed.
+   */
+  allowCustomWheelEvent(ev: WheelEvent): boolean;
 }
 
 export const ICoreService = createDecorator<ICoreService>('CoreService');