Fixes #20613: test for scrollbar/sliders before testing for view zones in mouse target

src/vs/editor/browser/controller/mouseTarget.ts

@@ -437,6 +437,7 @@ export class MouseTargetFactory {
 
 		result = result || MouseTargetFactory._hitTestContentWidget(ctx, request);
 		result = result || MouseTargetFactory._hitTestOverlayWidget(ctx, request);
+		result = result || MouseTargetFactory._hitTestScrollbarSlider(ctx, request);
 		result = result || MouseTargetFactory._hitTestViewZone(ctx, request);
 		result = result || MouseTargetFactory._hitTestMargin(ctx, request);
 		result = result || MouseTargetFactory._hitTestViewCursor(ctx, request);
@@ -584,6 +585,20 @@ export class MouseTargetFactory {
 		return this._createMouseTarget(ctx, request.withTarget(hitTestResult.hitTarget), true);
 	}
 
+	private static _hitTestScrollbarSlider(ctx: HitTestContext, request: HitTestRequest): MouseTarget {
+		if (ElementPath.isChildOfScrollableElement(request.targetPath)) {
+			if (request.target && request.target.nodeType === 1) {
+				let className = request.target.className;
+				if (className && /\b(slider|scrollbar)\b/.test(className)) {
+					const possibleLineNumber = ctx.getLineNumberAtVerticalOffset(request.mouseVerticalOffset);
+					const maxColumn = ctx.model.getLineMaxColumn(possibleLineNumber);
+					return request.fulfill(MouseTargetType.SCROLLBAR, new Position(possibleLineNumber, maxColumn));
+				}
+			}
+		}
+		return null;
+	}
+
 	private static _hitTestScrollbar(ctx: HitTestContext, request: HitTestRequest): MouseTarget {
 		// Is it the overview ruler?
 		// Is it a child of the scrollable element?