Support selectionForeground in dom

Part of #3810

src/browser/services/SelectionService.ts

@@ -308,6 +308,15 @@ export class SelectionService extends Disposable implements ISelectionService {
     return this._areCoordsInSelection(coords, start, end);
   }
 
+  public isCellInSelection(x: number, y: number): boolean {
+    const start = this._model.finalSelectionStart;
+    const end = this._model.finalSelectionEnd;
+    if (!start || !end) {
+      return false;
+    }
+    return this._areCoordsInSelection([x, y], start, end);
+  }
+
   protected _areCoordsInSelection(coords: [number, number], start: [number, number], end: [number, number]): boolean {
     return (coords[1] > start[1] && coords[1] < end[1]) ||
         (start[1] === end[1] && coords[1] === start[1] && coords[0] >= start[0] && coords[0] < end[0]) ||

src/browser/services/Services.ts

@@ -101,6 +101,7 @@ export interface ISelectionService {
   shouldForceSelection(event: MouseEvent): boolean;
   refresh(isLinuxMouseSelection?: boolean): void;
   onMouseDown(event: MouseEvent): void;
+  isCellInSelection(x: number, y: number): boolean;
 }
 
 export const ISoundService = createDecorator<ISoundService>('SoundService');