feat(dockview-modules): layout history (undo/redo) — Phases B–E

e2e/fixtures/index.html

@@ -44,6 +44,9 @@
                 const el = document.getElementById('app');
                 const dockview = new core.DockviewComponent(el, {
                     keyboardNavigation: true,
+                    // Record layout history so the harness can exercise undo/redo
+                    // (incl. async popout re-open).
+                    layoutHistory: { enabled: true },
                     // A served (not about:blank) target avoids a 404 when the
                     // popout window navigates before dockview injects content.
                     popoutUrl: '/e2e/fixtures/popout.html',
@@ -93,6 +96,13 @@
                     popoutActiveGroup: () =>
                         dockview.addPopoutGroup(dockview.activeGroup),
                     groupCount: () => dockview.groups.length,
+                    popoutCount: () => dockview.getPopouts().length,
+                    closeActivePopout: () =>
+                        dockview.getPopouts()[0].group.api.close(),
+                    undo: () => dockview.undo(),
+                    redo: () => dockview.redo(),
+                    canUndo: () => dockview.canUndo,
+                    awaitPopoutRestore: () => dockview.popoutRestorationPromise,
                 };
                 window.__ready = true;
             })();

e2e/tests/layout-history.spec.ts

@@ -0,0 +1,90 @@
+import { test, expect, Page } from '@playwright/test';
+
+/**
+ * Cross-window layout history (Phase D). Undo/redo restore the whole layout —
+ * including popout windows, which re-open **asynchronously**. The recorder holds
+ * its re-entrancy guard across that async re-open (so the re-open doesn't record
+ * a spurious entry) and exposes `popoutRestorationPromise` to await it. None of
+ * this is reachable in jsdom (no real second window).
+ */
+test.describe('cross-window layout history', () => {
+    const ready = async (page: Page) => {
+        await page.goto('/e2e/fixtures/index.html');
+        await page.waitForFunction(() => (window as any).__ready === true);
+        await page.evaluate(() => {
+            (window as any).__dv.addPanel('alpha');
+            (window as any).__dv.addPanel('beta');
+        });
+    };
+
+    test('undo reverts a popout (group returns to the grid)', async ({
+        page,
+        context,
+    }) => {
+        await ready(page);
+
+        const [win] = await Promise.all([
+            context.waitForEvent('page'),
+            page.evaluate(() => (window as any).__dv.popoutActiveGroup()),
+        ]);
+        await (win as Page).waitForLoadState();
+        expect(
+            await page.evaluate(() => (window as any).__dv.popoutCount())
+        ).toBe(1);
+
+        // Undo the popout → the window closes and the group goes back.
+        await Promise.all([
+            (win as Page).waitForEvent('close'),
+            page.evaluate(() => (window as any).__dv.undo()),
+        ]);
+        await expect
+            .poll(() => page.evaluate(() => (window as any).__dv.popoutCount()))
+            .toBe(0);
+    });
+
+    test('undo re-opens a closed popout window', async ({ page, context }) => {
+        await ready(page);
+
+        // pop the active group out
+        const [win1] = await Promise.all([
+            context.waitForEvent('page'),
+            page.evaluate(() => (window as any).__dv.popoutActiveGroup()),
+        ]);
+        await (win1 as Page).waitForLoadState();
+
+        // close the popout (records a removal whose pre-image still has the popout)
+        await Promise.all([
+            (win1 as Page).waitForEvent('close'),
+            page.evaluate(() => (window as any).__dv.closeActivePopout()),
+        ]);
+        expect(
+            await page.evaluate(() => (window as any).__dv.popoutCount())
+        ).toBe(0);
+        expect(await page.evaluate(() => (window as any).__dv.canUndo())).toBe(
+            true
+        );
+
+        // undo → re-opens the popout window asynchronously
+        const [win2] = await Promise.all([
+            context.waitForEvent('page'),
+            page.evaluate(async () => {
+                (window as any).__dv.undo();
+                await (window as any).__dv.awaitPopoutRestore();
+            }),
+        ]);
+        await (win2 as Page).waitForLoadState();
+        await expect
+            .poll(() => page.evaluate(() => (window as any).__dv.popoutCount()))
+            .toBe(1);
+
+        // The re-open must not have left a spurious history entry that a single
+        // redo can't account for — redo should cleanly close it again.
+        await Promise.all([
+            (win2 as Page).waitForEvent('close'),
+            page.evaluate(() => (window as any).__dv.redo()),
+        ]);
+        await expect
+            .poll(() => page.evaluate(() => (window as any).__dv.popoutCount()))
+            .toBe(0);
+    });
+});

packages/dockview-core/src/api/component.api.ts

@@ -46,6 +46,7 @@ import {
     IDockviewGroupPanel,
 } from '../dockview/dockviewGroupPanel';
 import { Event } from '../events';
+import { LayoutHistoryChangeEvent } from '../dockview/moduleContracts';
 import { IDockviewPanel } from '../dockview/dockviewPanel';
 import { PaneviewDidDropEvent } from '../paneview/draggablePaneviewPanel';
 import {
@@ -1020,6 +1021,50 @@ export class DockviewApi implements CommonApi<SerializedDockview> {
         this.component.withOrigin('api', () => this.component.clear());
     }
 
+    /**
+     * Undo the previous recorded layout mutation. No-op when there is nothing
+     * to undo, when `layoutHistory.enabled` is not set, or when the
+     * LayoutHistory module is absent.
+     */
+    undo(): void {
+        this.component.undo();
+    }
+
+    /** Re-apply the next layout mutation undone via {@link undo}. */
+    redo(): void {
+        this.component.redo();
+    }
+
+    /** Whether {@link undo} would do something. Reactive via {@link onDidChangeHistory}. */
+    get canUndo(): boolean {
+        return this.component.canUndo;
+    }
+
+    /** Whether {@link redo} would do something. */
+    get canRedo(): boolean {
+        return this.component.canRedo;
+    }
+
+    /** Drop both undo and redo stacks (e.g. on document switch). */
+    clearHistory(): void {
+        this.component.clearHistory();
+    }
+
+    /** Fires whenever the undo/redo stacks change. */
+    get onDidChangeHistory(): Event<LayoutHistoryChangeEvent> {
+        return this.component.onDidChangeHistory;
+    }
+
+    /**
+     * Resolves once any in-flight popout-window restoration completes. Popout
+     * windows re-open asynchronously, so after an {@link undo} / {@link redo} (or
+     * {@link fromJSON}) that re-opens a popout, await this to know the window is
+     * ready. Already-resolved when nothing is restoring.
+     */
+    get popoutRestorationPromise(): Promise<void> {
+        return this.component.popoutRestorationPromise;
+    }
+
     /**
      * Move the focus progmatically to the next panel or group.
      */

packages/dockview-core/src/dockview/dockviewComponent.ts

@@ -90,6 +90,8 @@ import {
     IAdvancedDnDHost,
     IContextMenuHost,
     IContextMenuService,
+    ILayoutHistoryHost,
+    LayoutHistoryChangeEvent,
     ITabGroupChipsHost,
 } from './moduleContracts';
 import { IHeaderActionsHost } from './headerActionsService';
@@ -423,8 +425,25 @@ export interface IDockviewComponent extends IBaseGrid<DockviewGroupPanel> {
     setEdgeGroupVisible(position: EdgeGroupPosition, visible: boolean): void;
     isEdgeGroupVisible(position: EdgeGroupPosition): boolean;
     removeEdgeGroup(position: EdgeGroupPosition): void;
+    // layout history (undo / redo)
+    undo(): void;
+    redo(): void;
+    readonly canUndo: boolean;
+    readonly canRedo: boolean;
+    clearHistory(): void;
+    readonly onDidChangeHistory: Event<LayoutHistoryChangeEvent>;
+    readonly popoutRestorationPromise: Promise<void>;
 }
 
+/** A never-firing history-change event — the fallback `onDidChangeHistory`
+ *  returns when the LayoutHistory module is absent, so the api event is always
+ *  valid and subscribable. */
+const NO_LAYOUT_HISTORY_CHANGES: Event<LayoutHistoryChangeEvent> = () => ({
+    dispose: () => {
+        // noop — nothing ever fires
+    },
+});
+
 let _hasWarnedUsingCoreDirectly = false;
 
 /**
@@ -471,7 +490,8 @@ export class DockviewComponent
         IHeaderActionsHost,
         IAdvancedDnDHost,
         ILiveRegionHost,
-        IAccessibilityHost
+        IAccessibilityHost,
+        ILayoutHistoryHost
 {
     private readonly nextGroupId = sequentialNumberGenerator();
     private readonly _deserializer = new DefaultDockviewDeserialzier(this);
@@ -765,6 +785,43 @@ export class DockviewComponent
         return this._moduleRegistry.services.headerActionsService;
     }
 
+    private get _layoutHistoryService() {
+        // Optional like every other module service; `?.`-guarded so the module
+        // can be removed from AllModules without crashing the component.
+        return this._moduleRegistry.services.layoutHistoryService;
+    }
+
+    /** Undo the previous recorded layout mutation (no-op if nothing to undo or
+     *  the LayoutHistory module is absent). Requires `layoutHistory.enabled`. */
+    undo(): void {
+        this._layoutHistoryService?.undo();
+    }
+
+    /** Re-apply the next layout mutation (no-op if nothing to redo). */
+    redo(): void {
+        this._layoutHistoryService?.redo();
+    }
+
+    get canUndo(): boolean {
+        return this._layoutHistoryService?.canUndo ?? false;
+    }
+
+    get canRedo(): boolean {
+        return this._layoutHistoryService?.canRedo ?? false;
+    }
+
+    /** Drop both undo and redo stacks. */
+    clearHistory(): void {
+        this._layoutHistoryService?.clear();
+    }
+
+    get onDidChangeHistory(): Event<LayoutHistoryChangeEvent> {
+        return (
+            this._layoutHistoryService?.onDidChangeHistory ??
+            NO_LAYOUT_HISTORY_CHANGES
+        );
+    }
+
     isGridEmpty(): boolean {
         return this.gridview.length === 0;
     }

packages/dockview-core/src/dockview/moduleContracts.ts

@@ -17,7 +17,10 @@ import { PopupService } from './components/popupService';
 import { DockviewComponentOptions } from './options';
 import {
     DockviewLayoutMutationEvent,
+    DockviewLayoutMutationKind,
+    DockviewOrigin,
     GroupNavigationDirection,
+    SerializedDockview,
 } from './dockviewComponent';
 import { DockviewWillDropEvent } from './dockviewGroupPanelModel';
 import {
@@ -189,3 +192,56 @@ export interface IAdvancedDnDService extends IDisposable {
         position: Position
     ): IDisposable;
 }
+
+// --- LayoutHistory ---
+
+/**
+ * The narrow surface the layout-history service needs from the host
+ * (`DockviewComponent`). It reads/writes whole-layout snapshots and listens to
+ * the mutation-transaction boundary — the only place a *pre-image* can be taken
+ * before a mutation runs.
+ */
+export interface ILayoutHistoryHost {
+    readonly options: DockviewComponentOptions;
+    toJSON(): SerializedDockview;
+    fromJSON(
+        data: SerializedDockview,
+        options?: { reuseExistingPanels: boolean }
+    ): void;
+    /** Fires before a structural mutation — used to capture the pre-image. */
+    readonly onWillMutateLayout: Event<DockviewLayoutMutationEvent>;
+    /** Fires after a structural mutation — used to capture the post-image. */
+    readonly onDidMutateLayout: Event<DockviewLayoutMutationEvent>;
+    /** Coalesced (microtask-buffered) ping after any layout change — the only
+     *  signal for sash resize, which does not go through the mutation boundary. */
+    readonly onDidLayoutChange: Event<void>;
+    /** Settles once any in-flight popout-window restoration (from `fromJSON`)
+     *  completes. Popouts re-open asynchronously, so undo/redo holds its guard
+     *  until this resolves. Already-resolved when nothing is restoring. */
+    readonly popoutRestorationPromise: Promise<void>;
+}
+
+/** Entry labels — the mutation kinds plus the synthetic `'resize'` (sash drag,
+ *  which has no mutation-boundary kind of its own). */
+export type LayoutHistoryKind = DockviewLayoutMutationKind | 'resize';
+
+export interface LayoutHistoryChangeEvent {
+    readonly canUndo: boolean;
+    readonly canRedo: boolean;
+    readonly undoCount: number;
+    readonly redoCount: number;
+    readonly lastEntry?: {
+        kind: LayoutHistoryKind;
+        origin: DockviewOrigin;
+    };
+}
+
+export interface ILayoutHistoryService extends IDisposable {
+    readonly canUndo: boolean;
+    readonly canRedo: boolean;
+    readonly onDidChangeHistory: Event<LayoutHistoryChangeEvent>;
+    undo(): void;
+    redo(): void;
+    /** Drop both stacks (e.g. on document switch). */
+    clear(): void;
+}

packages/dockview-core/src/dockview/modules.ts

@@ -22,6 +22,7 @@ import {
     IAdvancedDnDService,
     IContextMenuService,
     IKeyboardDockingService,
+    ILayoutHistoryService,
     ITabGroupChipsService,
 } from './moduleContracts';
 
@@ -38,6 +39,7 @@ export interface ServiceCollection {
     liveRegionService?: ILiveRegionService;
     accessibilityService?: IAccessibilityService;
     keyboardDockingService?: IKeyboardDockingService;
+    layoutHistoryService?: ILayoutHistoryService;
 }
 
 export interface DockviewModule<THost = unknown> {