Only swap Alt-hold close action for the hovered tab in MultiEditorTabsControl (#331772)

* Initial plan

* Only swap Alt-hold close action for the hovered tab

Co-authored-by: benibenj <44439583+benibenj@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: benibenj <44439583+benibenj@users.noreply.github.com>

Author: Copilot

src/vs/workbench/browser/parts/editor/multiEditorTabsControl.ts

@@ -120,8 +120,9 @@ export class MultiEditorTabsControl extends EditorTabsControl {
 	private readonly unpinEditorAction = this._register(this.instantiationService.createInstance(UnpinEditorAction, UnpinEditorAction.ID, UnpinEditorAction.LABEL));
 	private readonly closeOtherEditorTabsInGroupAction = this._register(this.instantiationService.createInstance(CloseOtherEditorTabsInGroupAction, CloseOtherEditorTabsInGroupAction.ID, CloseOtherEditorTabsInGroupAction.LABEL));
 
-	// Alt-hold alternative to a tab's close action (JetBrains-style); see updateTabActionsForAltState().
-	private wantsCloseOthersAction: boolean;
+	// Alt-hold alternative to a tab's close action (JetBrains-style), applied only
+	// to the currently hovered tab; see updateTabActionForHoveredTab().
+	private hoveredTabIndex: number | undefined;
 
 	private readonly tabResourceLabels = this._register(this.instantiationService.createInstance(ResourceLabels, DEFAULT_LABELS_CONTAINER));
 	private tabLabels: IEditorInputLabel[] = [];
@@ -175,24 +176,47 @@ export class MultiEditorTabsControl extends EditorTabsControl {
 		// React to decorations changing for our resource labels
 		this._register(this.tabResourceLabels.onDidChangeDecorations(() => this.doHandleDecorationsChange()));
 
-		// React to Alt being held/released to swap in the "Close Others" tab action. Initialize
-		// from the current state too, in case this control is created mid-hold.
-		this.wantsCloseOthersAction = modifierKeyEmitter.keyStatus.altKey;
-		this._register(modifierKeyEmitter.event(() => this.updateTabActionsForAltState()));
+		// React to Alt being held/released to swap in the "Close Others" tab action
+		// for the currently hovered tab only (if any).
+		this._register(modifierKeyEmitter.event(() => this.updateTabActionForHoveredTab()));
 	}
 
-	private updateTabActionsForAltState(): void {
-		const wantsCloseOthersAction = modifierKeyEmitter.keyStatus.altKey;
-		if (wantsCloseOthersAction === this.wantsCloseOthersAction) {
+	private updateTabActionForHoveredTab(): void {
+		if (typeof this.hoveredTabIndex !== 'number') {
+			return; // no tab hovered, nothing to update
+		}
+
+		this.redrawTabActionAtIndex(this.hoveredTabIndex);
+	}
+
+	private redrawTabActionAtIndex(tabIndex: number): void {
+		const editor = this.tabsModel.getEditorByIndex(tabIndex);
+		if (editor) {
+			this.doWithTab(tabIndex, editor, (editor, tabIndex, tabContainer, tabLabelWidget, tabLabel, tabActionBar) => this.redrawTabAction(editor, tabIndex, tabContainer, tabActionBar));
+		}
+	}
+
+	// Tracks which tab (if any) the mouse is currently over so the Alt-hold "Close
+	// Others" swap (see redrawTabAction()) applies only to that single tab.
+	private setHoveredTab(tabIndex: number | undefined): void {
+		if (this.hoveredTabIndex === tabIndex) {
 			return;
 		}
 
-		this.wantsCloseOthersAction = wantsCloseOthersAction;
+		const previousHoveredTabIndex = this.hoveredTabIndex;
+		this.hoveredTabIndex = tabIndex;
 
-		// Only the action items need to change here, not labels/decorations/toolbar/layout.
-		this.forEachTab((editor, tabIndex, tabContainer, tabLabelWidget, tabLabel, tabActionBar) => {
-			this.redrawTabAction(editor, tabIndex, tabContainer, tabActionBar);
-		});
+		if (!modifierKeyEmitter.keyStatus.altKey) {
+			return; // Alt is not held, no action swap in effect to redraw
+		}
+
+		if (typeof previousHoveredTabIndex === 'number') {
+			this.redrawTabActionAtIndex(previousHoveredTabIndex);
+		}
+
+		if (typeof tabIndex === 'number') {
+			this.redrawTabActionAtIndex(tabIndex);
+		}
 	}
 
 	protected override create(parent: HTMLElement): HTMLElement {
@@ -397,6 +421,11 @@ export class MultiEditorTabsControl extends EditorTabsControl {
 			}
 		}));
 
+		// Clear the hovered tab once the mouse leaves the tabs container entirely
+		this._register(addDisposableListener(tabsContainer, EventType.MOUSE_LEAVE, () => {
+			this.setHoveredTab(undefined);
+		}));
+
 		// Prevent auto-pasting (https://github.com/microsoft/vscode/issues/201696)
 		if (isLinux) {
 			this._register(addDisposableListener(tabsContainer, EventType.MOUSE_UP, e => {
@@ -666,6 +695,12 @@ export class MultiEditorTabsControl extends EditorTabsControl {
 
 	private handleClosedEditors(): void {
 
+		// A stale hovered tab index could otherwise leave a tab
+		// showing "Close Others" after the tabs it pointed past got removed
+		if (typeof this.hoveredTabIndex === 'number' && this.hoveredTabIndex >= this.tabsModel.count) {
+			this.setHoveredTab(undefined);
+		}
+
 		// There are tabs to show
 		if (this.tabsModel.count) {
 
@@ -1023,6 +1058,17 @@ export class MultiEditorTabsControl extends EditorTabsControl {
 		disposables.add(addDisposableListener(tab, EventType.MOUSE_DOWN, e => handleClickOrTouch(e, false)));
 		disposables.add(addDisposableListener(tab, TouchEventType.Tap, (e: GestureEvent) => handleClickOrTouch(e, true))); // Preserve focus on touch #125470
 
+		// Track hover so the Alt-hold "Close Others" action swap (see redrawTabAction())
+		// only applies to the tab the mouse is currently over.
+		disposables.add(addDisposableListener(tab, EventType.MOUSE_ENTER, () => {
+			this.setHoveredTab(tabIndex);
+		}));
+		disposables.add(addDisposableListener(tab, EventType.MOUSE_LEAVE, () => {
+			if (this.hoveredTabIndex === tabIndex) {
+				this.setHoveredTab(undefined);
+			}
+		}));
+
 		// Touch Scroll Support
 		disposables.add(addDisposableListener(tab, TouchEventType.Change, (e: GestureEvent) => {
 			tabsScrollbar.setScrollPosition({ scrollLeft: tabsScrollbar.getScrollPosition().scrollLeft - e.translationX });
@@ -1622,8 +1668,9 @@ export class MultiEditorTabsControl extends EditorTabsControl {
 		const hasCloseAction = isCloseable && !hasUnpinAction && options.tabActionCloseVisibility;
 		const hasAction = hasUnpinAction || hasCloseAction;
 
-		// Alt swaps a visible Close action to Close Others; Unpin is unaffected.
-		const wantsCloseOthersAction = hasCloseAction && this.wantsCloseOthersAction;
+		// Alt swaps a visible Close action to Close Others, but only for the
+		// currently hovered tab; Unpin is unaffected.
+		const wantsCloseOthersAction = hasCloseAction && modifierKeyEmitter.keyStatus.altKey && tabIndex === this.hoveredTabIndex;
 		this.closeOtherEditorTabsInGroupAction.enabled = this.groupView.count > 1;
 
 		let tabAction;