Show only the game view in fullscreen, in the editor and the link (#267)

A game is easier to judge and to play without the editor around it.
The Game tab and the game link now both have a button that puts the
game view itself into fullscreen, not just the browser window.

- The Game tab header has a fullscreen button on the right. It hides
  toolbar, panels, tab headers and console and keeps the zoom from the
  picker. A running game keeps running.
- A corner button at the top right, or Esc, leaves fullscreen and puts
  the view back into the tab where it was.
- The game link shows the same corner button. Over a running game it
  hides after 2 s without mouse movement and returns on the next move.
- A click on the corner button never reaches the game.
- Stop ends fullscreen. Stop switches back to the Scene tab, and any
  switch away from the Game tab ends fullscreen, so no empty screen is
  left behind.
- src/viewport/fullscreen.ts wraps the Fullscreen API and holds the
  rule for when the button shows. FullscreenCorner.ts is the button
  used by both pages. Two SVG icons are new.
- Editor.showGameFullscreen moves the GameViewport into the root while
  fullscreen is on.

Tests:
- ./check.sh: 195 files, 2815 tests, exit 0 (3 new unit tests).
- e2e 60: 2 new checks for the corner button on the game link.
- e2e 61 (new): 4 checks for fullscreen in the editor.
- Full e2e run (local): ALL PASSED, 1580 checks.
- Counter-checks fail as expected: rule without "no game running",
  no stopPropagation (60h), no end on tab switch (61c), no reparenting
  of the view (61a).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -43,7 +43,7 @@ npm run build        # writes dist/ and regenerates index.html; the folder is wh
 The browser suite and the three example games need a machine with a GPU:
 
 ```bash
-node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1574 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1580 checks (GM_STEPS=20 for one step)
                                                    #   every tool signs in first – see the Accounts page
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs
 node tools/seed-tetris.mjs && node tools/smoke-tetris.mjs

src/editor/Editor.ts

@@ -33,6 +33,7 @@ import { GamePane } from './viewport/GamePane';
 import { ScenePane } from './viewport/ScenePane';
 import { GameViewport } from './viewport/GameViewport';
 import { SceneViewport } from './viewport/SceneViewport';
+import { leaveFullscreen, onFullscreenChange } from '../viewport/fullscreen';
 import { TAB_OF_ASSET } from './assetTabs';
 import { attachAutosave } from './autosave';
 import { PasswordDialog } from './auth/PasswordDialog';
@@ -463,6 +464,8 @@ export class Editor implements PlayHost {
     const onTick = (ticker: Ticker) => this.tick(ticker.deltaMS / 1000);
     app.ticker.add(onTick);
     this.cleanups.push(() => app.ticker.remove(onTick));
+    // Only the game tab's button asks for fullscreen, so every change is the game view's (#267).
+    this.cleanups.push(onFullscreenChange((on) => this.showGameFullscreen(on)));
     // In the game view Tab is a game key (an inventory, a target switch) – like every other key there.
     const focus = ui().focus;
     focus.tabBelongsElsewhere = () => this.tab === 'game';
@@ -690,6 +693,28 @@ export class Editor implements PlayHost {
     else this.showTab(tab);
   }
 
+  /**
+   * In fullscreen the game view is all the page shows: it moves from its tab to the root, and the
+   * toolbar and the workspace step aside. Leaving puts it back where it was, below the tab header.
+   */
+  private showGameFullscreen(on: boolean): void {
+    if (on === this.gameView.isFullscreen) return;
+    this.toolbar.visible = !on;
+    this.workspace.visible = !on;
+    if (on) this.root.add(this.gameView, 1);
+    else this.gamePane.add(this.gameView, 1);
+    this.gameView.setFullscreen(on);
+    this.root.relayout();
+    // The pane may come back at the size it had, and a resize to the same size lays nothing out.
+    this.gamePane.relayout();
+  }
+
+  /** Back to the editor now, not when the browser reports it: the caller goes on with the layout. */
+  private endGameFullscreen(): void {
+    leaveFullscreen();
+    this.showGameFullscreen(false);
+  }
+
   private kindOf(doc: DocumentId): CentreTab | null {
     if (doc.startsWith('values:')) {
       const target = this.valueTargets.get(doc);
@@ -754,6 +779,8 @@ export class Editor implements PlayHost {
 
   /** Shows the pane for `tab`, with `strip` lit in the row – none for an empty kind reached by `showTab`. */
   private display(tab: TabId, strip: StripTab | null): void {
+    // Fullscreen is the game view's; a tab that takes its place (Stop goes back to the scene) ends it.
+    if (tab !== 'game') this.endGameFullscreen();
     this.tab = tab;
     this.documents = { docs: this.documents.docs, active: strip && isDocument(strip) ? strip : null };
     // The hierarchy lists what the visible tab edits; every other tab is about the scene.
@@ -817,6 +844,7 @@ export class Editor implements PlayHost {
   async dispose(): Promise<void> {
     if (this.disposed) return;
     this.disposed = true;
+    this.endGameFullscreen();
     await this.autosave.flush();
     this.autosave.stop();
     if (this.play.isPlaying) this.play.stop();

src/editor/debug/hookHelpers.ts

@@ -1,4 +1,5 @@
-import type { Application } from 'pixi.js';
+import type { Application, Container } from 'pixi.js';
+import { ui } from '../../ui';
 import type { Editor } from '../Editor';
 import type { SnapToggle } from '../graph/SnapToggle';
 import type { EditorState } from '../state';
@@ -18,6 +19,16 @@ export function centreOf(widget: { getGlobalPosition(): { x: number; y: number }
   return { x: p.x + widget.w / 2, y: p.y + widget.h / 2 };
 }
 
+/** Whether `node` and everything it hangs from are visible, up to a stage. */
+export function shownOnStage(node: Container): boolean {
+  let current = node;
+  while (current.visible) {
+    if (!current.parent) return current === ui().app.stage;
+    current = current.parent;
+  }
+  return false;
+}
+
 /** A tab's magnet (#194): where to click it, how big it is drawn, and whether it is on. */
 export function snapButton(snap: SnapToggle): {
   x: number;

src/editor/debug/sceneHooks.ts

@@ -5,7 +5,7 @@ import { currentVisibilityPopup } from '../panels/SceneVisibilityPopup';
 import { currentTilemapWidgets, paintedLayerId, paintedTilemap } from '../panels/TilemapPanel';
 import type { TilemapTool } from '../state';
 import { rectOf } from '../textProbe';
-import { centreOf, type HookContext } from './hookHelpers';
+import { centreOf, type HookContext, shownOnStage } from './hookHelpers';
 
 /** The Scene and Game tabs, the tilemap painted in the scene view, and the Container tab. */
 export function sceneHooks({ state, editor }: HookContext) {
@@ -96,6 +96,16 @@ export function sceneHooks({ state, editor }: HookContext) {
         picker: centreOf(gamePane.scalePicker),
       };
     },
+    /**
+     * Fullscreen of the game view (#267): whether the view is moved to the root, whether the browser
+     * is in fullscreen, the header button, and the corner button while it shows.
+     */
+    gameFullscreen: () => ({
+      on: gameView.isFullscreen,
+      document: document.fullscreenElement !== null,
+      headerButton: shownOnStage(gamePane.fullscreenButton) ? centreOf(gamePane.fullscreenButton) : null,
+      corner: shownOnStage(gameView.fullscreenButton) ? centreOf(gameView.fullscreenButton) : null,
+    }),
     /** Which typeface a text ended up drawn in, and how wide it made it. */
     textInfo: (id: string) => viewport.textInfo(id),
     gameTextInfo: (id: string) => gameView.textInfo(id),

src/editor/viewport/GamePane.ts

@@ -1,4 +1,5 @@
-import { Dropdown, Menu, type MenuItem, VStack } from '../../ui';
+import { Button, Dropdown, Menu, type MenuItem, Spacer, Theme, UI_ICON_SVG, VStack } from '../../ui';
+import { toggleFullscreen } from '../../viewport/fullscreen';
 import { GAME_SCALE_STEPS, type GameScale } from '../../viewport/view';
 import { TabHeader } from '../TabHeader';
 import type { GameViewport } from './GameViewport';
@@ -6,11 +7,16 @@ import type { GameViewport } from './GameViewport';
 /** Room for the longest label, "Auto · 400%". */
 const SCALE_WIDTH = 110;
 
-/** The game tab (#225): a header with the scale picker above the game view. */
+/** The game tab (#225): a header with the scale picker and the fullscreen button above the game view. */
 export class GamePane extends VStack {
   readonly header = new TabHeader();
   /** Public for the check scripts. */
   readonly scalePicker: Dropdown;
+  readonly fullscreenButton = new Button('', {
+    width: Theme.controlHeight,
+    icon: UI_ICON_SVG.fullscreen,
+    onClick: () => void toggleFullscreen(),
+  });
 
   constructor(readonly view: GameViewport) {
     super();
@@ -19,6 +25,8 @@ export class GamePane extends VStack {
       onClick: () => this.openScalePicker(),
     });
     this.header.add(this.scalePicker);
+    this.header.add(new Spacer(), 1);
+    this.header.add(this.fullscreenButton);
     this.add(this.header);
     this.add(view, 1);
     view.onScaleShown = (factor) => this.scalePicker.setText(scaleLabel(view.scaleMode, factor));

src/editor/viewport/GameViewport.ts

@@ -8,6 +8,7 @@ import type { EditorState } from '../state';
 import type { World } from '../../runtime/World';
 import { Theme, textStyle, ui } from '../../ui';
 import { type ActiveCamera, cameraOfItems, cameraOfWorld } from '../../viewport/activeCamera';
+import { FullscreenCorner } from '../../viewport/FullscreenCorner';
 import { collectHolderItems, collectWorldItems } from '../../viewport/items';
 import { routePointer } from '../../viewport/gamePointer';
 import { cameraFactor, cameraView, type GameScale, type View } from '../../viewport/view';
@@ -26,6 +27,9 @@ export class GameViewport extends WorldViewport<EditorState> {
   private factor: number | null = null;
   /** Told the factor of every redraw: auto and fit change with the view. */
   onScaleShown: ((factor: number | null) => void) | null = null;
+  /** The way back out of fullscreen (#267); the tab header has the way in. */
+  readonly fullscreenButton = new FullscreenCorner(this);
+  private fullscreen = false;
 
   constructor(state: EditorState) {
     super(state);
@@ -34,6 +38,8 @@ export class GameViewport extends WorldViewport<EditorState> {
     this.addChild(this.hint);
     this.editorRunCaption.eventMode = 'none';
     this.addChild(this.editorRunCaption);
+    this.addChild(this.fullscreenButton);
+    this.fullscreenButton.sync(false, false);
     routePointer(
       this,
       () => this.pointerWorld(),
@@ -44,9 +50,20 @@ export class GameViewport extends WorldViewport<EditorState> {
   /** null = not playing. */
   setWorld(world: World | null): void {
     this.playWorld = world;
+    this.fullscreenButton.sync(this.fullscreen, world !== null);
     this.redraw();
   }
 
+  get isFullscreen(): boolean {
+    return this.fullscreen;
+  }
+
+  /** Whether this view is all the screen shows; the editor moves it there and back. */
+  setFullscreen(on: boolean): void {
+    this.fullscreen = on;
+    this.fullscreenButton.sync(on, this.playWorld !== null);
+  }
+
   /** null = no behavior is running outside play mode. */
   setEditorWorld(world: World | null): void {
     this.editorWorld = world;
@@ -134,5 +151,6 @@ export class GameViewport extends WorldViewport<EditorState> {
     // Which tab holds the keyboard is otherwise nowhere to be seen.
     this.editorRunCaption.visible = this.editorWorld !== null && !this.playWorld;
     this.editorRunCaption.position.set(8, 6);
+    this.fullscreenButton.place(this.w);
   }
 }

src/player/GameScreen.ts

@@ -2,6 +2,7 @@ import { Text, type TextStyle } from 'pixi.js';
 import type { World } from '../runtime/World';
 import { Theme, textStyle, ui } from '../ui';
 import { cameraOfWorld } from '../viewport/activeCamera';
+import { FullscreenCorner } from '../viewport/FullscreenCorner';
 import { routePointer } from '../viewport/gamePointer';
 import { collectWorldItems } from '../viewport/items';
 import { cameraView, type View } from '../viewport/view';
@@ -27,6 +28,7 @@ export class GameScreen extends WorldViewport {
   /** Asked when the caption is clicked while it offers to start. */
   onStart: (() => void) | null = null;
   private startable = false;
+  readonly fullscreenButton = new FullscreenCorner(this);
 
   constructor(source: ViewSource) {
     super(source);
@@ -35,6 +37,7 @@ export class GameScreen extends WorldViewport {
       text.anchor.set(0.5);
       this.addChild(text);
     }
+    this.addChild(this.fullscreenButton);
     routePointer(
       this,
       () => this.running,
@@ -59,6 +62,7 @@ export class GameScreen extends WorldViewport {
   /** null = not running. */
   setWorld(world: World | null): void {
     this.running = world;
+    this.fullscreenButton.sync(true, world !== null);
     this.redraw();
   }
 
@@ -101,5 +105,6 @@ export class GameScreen extends WorldViewport {
     this.caption.position.set(this.w / 2, this.h / 2);
     this.hint.visible = this.running !== null && view === null;
     this.hint.position.set(this.w / 2, this.h / 2);
+    this.fullscreenButton.place(this.w);
   }
 }

src/player/playerHook.ts

@@ -13,5 +13,14 @@ export function installPlayerHook(screen: GameScreen, player: () => Player | nul
     screen: () => screen.info(),
     log: () => player()?.log() ?? [],
     pixelAt: (x: number, y: number) => stagePixel(ui().app, x, y),
+    /** Whether the page is in fullscreen, and the corner button while it shows (#267). */
+    fullscreen: () => {
+      const button = screen.fullscreenButton;
+      const origin = button.getGlobalPosition();
+      return {
+        on: document.fullscreenElement !== null,
+        button: button.visible ? { x: origin.x + button.w / 2, y: origin.y + button.h / 2 } : null,
+      };
+    },
   };
 }

src/ui/icons.ts

@@ -3,7 +3,9 @@
  * come from whatever font the system has, so they are SVG files like every other icon.
  */
 import current from './icons/current.svg?raw';
+import fullscreenExit from './icons/fullscreen-exit.svg?raw';
+import fullscreen from './icons/fullscreen.svg?raw';
 import ticked from './icons/ticked.svg?raw';
 import unticked from './icons/unticked.svg?raw';
 
-export const UI_ICON_SVG = { current, ticked, unticked };
+export const UI_ICON_SVG = { current, fullscreen, fullscreenExit, ticked, unticked };

src/ui/icons/fullscreen-exit.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" id="fullscreen-exit" viewBox="-8 -8 16 16" width="16" height="16">
+  <path d="M-6 -2 L-2 -2 L-2 -6" fill="none" stroke="currentColor" stroke-width="1.5" />
+  <path d="M2 -6 L2 -2 L6 -2" fill="none" stroke="currentColor" stroke-width="1.5" />
+  <path d="M6 2 L2 2 L2 6" fill="none" stroke="currentColor" stroke-width="1.5" />
+  <path d="M-2 6 L-2 2 L-6 2" fill="none" stroke="currentColor" stroke-width="1.5" />
+</svg>

src/ui/icons/fullscreen.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" id="fullscreen" viewBox="-8 -8 16 16" width="16" height="16">
+  <path d="M-6 -2 L-6 -6 L-2 -6" fill="none" stroke="currentColor" stroke-width="1.5" />
+  <path d="M2 -6 L6 -6 L6 -2" fill="none" stroke="currentColor" stroke-width="1.5" />
+  <path d="M6 2 L6 6 L2 6" fill="none" stroke="currentColor" stroke-width="1.5" />
+  <path d="M-2 6 L-6 6 L-6 2" fill="none" stroke="currentColor" stroke-width="1.5" />
+</svg>

src/viewport/FullscreenCorner.ts

@@ -0,0 +1,78 @@
+import type { Container, FederatedPointerEvent } from 'pixi.js';
+import { Button, requestRender, Theme, UI_ICON_SVG } from '../ui';
+import {
+  CORNER_BUTTON_IDLE_SECONDS,
+  isFullscreen,
+  onFullscreenChange,
+  showsCornerButton,
+  toggleFullscreen,
+} from './fullscreen';
+
+/**
+ * The fullscreen button in the top right corner of a game on screen (#267): on the player page
+ * always, in the editor while its game view is in fullscreen. Over a running game it steps aside
+ * once the mouse rests (`showsCornerButton`).
+ */
+export class FullscreenCorner extends Button {
+  private active = true;
+  private running = false;
+  private lastMove = performance.now();
+  private hideTimer = 0;
+  private readonly stopChange: () => void;
+
+  constructor(host: Container) {
+    super('', {
+      width: Theme.controlHeight,
+      icon: isFullscreen() ? UI_ICON_SVG.fullscreenExit : UI_ICON_SVG.fullscreen,
+      onClick: () => void toggleFullscreen(),
+    });
+    this.focusable = false;
+    this.resize(Theme.controlHeight, Theme.controlHeight);
+    // The button lies on the game: a press on it must neither start the game nor reach it as a click.
+    const keep = (e: FederatedPointerEvent): void => e.stopPropagation();
+    this.on('pointerdown', keep);
+    this.on('pointerup', keep);
+    this.on('pointerover', () => this.refresh());
+    this.on('pointerout', () => this.refresh());
+    host.on('globalpointermove', () => {
+      this.lastMove = performance.now();
+      this.refresh();
+    });
+    this.stopChange = onFullscreenChange((on) =>
+      this.setIcon(on ? UI_ICON_SVG.fullscreenExit : UI_ICON_SVG.fullscreen),
+    );
+  }
+
+  override destroy(options?: Parameters<Button['destroy']>[0]): void {
+    this.stopChange();
+    window.clearTimeout(this.hideTimer);
+    super.destroy(options);
+  }
+
+  /** `active`: whether the host wants the button at all; `running`: whether a game is on screen. */
+  sync(active: boolean, running: boolean): void {
+    this.active = active;
+    this.running = running;
+    this.refresh();
+  }
+
+  /** Top right, a gap in from both edges of a host `w` wide. */
+  place(w: number): void {
+    this.position.set(Math.round(w - this.w - Theme.gap * 2), Theme.gap * 2);
+  }
+
+  private refresh(): void {
+    window.clearTimeout(this.hideTimer);
+    const idleSeconds = (performance.now() - this.lastMove) / 1000;
+    const show =
+      this.active && showsCornerButton({ running: this.running, idleSeconds, overButton: this.hovered });
+    if (show !== this.visible) {
+      this.visible = show;
+      requestRender();
+    }
+    if (show && this.running && !this.hovered) {
+      const left = CORNER_BUTTON_IDLE_SECONDS - idleSeconds;
+      this.hideTimer = window.setTimeout(() => this.refresh(), Math.max(0, left * 1000) + 20);
+    }
+  }
+}

src/viewport/fullscreen.ts

@@ -0,0 +1,44 @@
+/**
+ * Fullscreen for the game view (#267): the browser's Fullscreen API on the whole page, which is the
+ * one canvas. What the canvas then shows – only the game – is up to the page that asked.
+ */
+
+/** How long the corner button stays after the mouse last moved over a running game. */
+export const CORNER_BUTTON_IDLE_SECONDS = 2;
+
+/**
+ * Whether the corner button shows: always while no game runs, and over a running game only while
+ * the mouse moves or rests on the button – it would otherwise sit over the picture for good.
+ */
+export function showsCornerButton(state: {
+  running: boolean;
+  idleSeconds: number;
+  overButton: boolean;
+}): boolean {
+  return !state.running || state.overButton || state.idleSeconds < CORNER_BUTTON_IDLE_SECONDS;
+}
+
+export function isFullscreen(): boolean {
+  return document.fullscreenElement !== null;
+}
+
+/** Enters or leaves fullscreen; a browser that refuses leaves everything as it was. */
+export async function toggleFullscreen(): Promise<void> {
+  try {
+    if (isFullscreen()) await document.exitFullscreen();
+    else await document.documentElement.requestFullscreen();
+  } catch (error) {
+    console.warn('[fullscreen]', error);
+  }
+}
+
+export function leaveFullscreen(): void {
+  if (isFullscreen()) void document.exitFullscreen().catch((error) => console.warn('[fullscreen]', error));
+}
+
+/** Calls `handler` whenever fullscreen starts or ends, by the button or by Esc; returns the call that stops it. */
+export function onFullscreenChange(handler: (on: boolean) => void): () => void {
+  const listener = (): void => handler(isFullscreen());
+  document.addEventListener('fullscreenchange', listener);
+  return () => document.removeEventListener('fullscreenchange', listener);
+}

tests/viewport/fullscreen.test.ts

@@ -0,0 +1,23 @@
+/** When the fullscreen button in the corner of a game shows (#267). */
+import { describe, expect, it } from 'vitest';
+import { CORNER_BUTTON_IDLE_SECONDS, showsCornerButton } from '../../src/viewport/fullscreen';
+
+describe('showsCornerButton', () => {
+  it('always shows while no game runs, however long the mouse rests', () => {
+    expect(showsCornerButton({ running: false, idleSeconds: 60, overButton: false })).toBe(true);
+  });
+
+  it('shows over a running game only while the mouse moved lately', () => {
+    expect(showsCornerButton({ running: true, idleSeconds: 0, overButton: false })).toBe(true);
+    expect(
+      showsCornerButton({ running: true, idleSeconds: CORNER_BUTTON_IDLE_SECONDS - 0.1, overButton: false }),
+    ).toBe(true);
+    expect(
+      showsCornerButton({ running: true, idleSeconds: CORNER_BUTTON_IDLE_SECONDS, overButton: false }),
+    ).toBe(false);
+  });
+
+  it('stays while the pointer rests on it', () => {
+    expect(showsCornerButton({ running: true, idleSeconds: 60, overButton: true })).toBe(true);
+  });
+});

tools/e2e/60-release.mjs

@@ -77,8 +77,8 @@ function game(id) {
 
 /**
  * Releasing a project (#266): published from the main menu, played from the link without a
- * session – only the game, zoomed to Auto, on the page colour – updated under the same link, and
+ * session – only the game, zoomed to Auto, on the page colour, with a fullscreen button in the
- * taken down.
+ * corner (#267) – updated under the same link, and taken down.
  *
  * Works on a throwaway project of its own, like step 50. The last thing it does is delete that
  * project and open the fixture again.
@@ -230,6 +230,7 @@ export async function release(t) {
     await click(size.w / 2, size.h / 2);
     await waitUntil('__gameMakerPlay.running()', { label: 'the game runs' });
     await sleep(300);
+    const cornerAfterClick = await player('fullscreen()');
     const screen = await player('screen()');
     const centre = { x: screen.frame.x + screen.frame.w / 2, y: screen.frame.y + screen.frame.h / 2 };
     const scale = screen.scale;
@@ -256,6 +257,23 @@ export async function release(t) {
       playingCursor,
     );
 
+    // 60g (#267). The fullscreen button sits in the top right corner while the mouse moves, steps
+    // aside once it rests over the running game, and is back with the next move.
+    await sleep(2300);
+    const rested = await player('fullscreen()');
+    await t.mouse('mouseMoved', size.w / 2 + 30, size.h / 2 + 30);
+    await settle();
+    const movedAgain = await player('fullscreen()');
+    check(
+      'over a running game the fullscreen button shows while the mouse moves and steps aside when it rests',
+      cornerAfterClick.button !== null &&
+        cornerAfterClick.button.x > size.w - 60 &&
+        cornerAfterClick.button.y < 60 &&
+        rested.button === null &&
+        movedAgain.button !== null,
+      JSON.stringify({ cornerAfterClick, rested, movedAgain }),
+    );
+
     // 60e. The keys go to the game: the arrow moves the crate out of the middle, S stops the game.
     await holdKey('ArrowRight', 500);
     await sleep(200);
@@ -267,6 +285,22 @@ export async function release(t) {
       moved === BACKGROUND && (await player('screen()')).caption === 'Click to play again',
       JSON.stringify({ moved, screen: await player('screen()') }),
     );
+
+    // 60h (#267). A click on the corner button makes the page fullscreen and does not reach the
+    // game – it would start it again; a second click leaves fullscreen.
+    const corner = (await player('fullscreen()')).button;
+    if (corner) await click(corner.x, corner.y);
+    await sleep(500);
+    const entered = { ...(await player('fullscreen()')), running: await player('running()') };
+    const exitAt = entered.button ?? corner;
+    if (exitAt) await click(exitAt.x, exitAt.y);
+    await sleep(500);
+    const left = await player('fullscreen()');
+    check(
+      'the corner button puts the page into fullscreen and back, without starting the game',
+      corner !== null && entered.on && !entered.running && !left.on,
+      JSON.stringify({ corner, entered, left }),
+    );
     check('the play page threw nothing', exceptions().length === 0, exceptions().join(' | '));
 
     // 60f. Take down asks, then the link is dead – for the API and for the page.

tools/e2e/61-fullscreen.mjs

@@ -0,0 +1,64 @@
+/**
+ * Fullscreen of the game tab (#267): the button in its header puts the game view on its own into
+ * fullscreen – no toolbar, no panels, no header –, the game keeps running, and the button in the
+ * corner puts the view back under its header. Stopping the game from fullscreen ends it as well.
+ */
+export async function fullscreen(t) {
+  const { check, json, click, sleep, play, stop, shot, press, exceptions } = t;
+  const info = async () => ({
+    ...(await json('__gm.gameFullscreen()')),
+    view: (await json('__gm.gameScale()')).view,
+  });
+  const size = { w: await json('innerWidth'), h: await json('innerHeight') };
+
+  await press('Escape');
+  await play();
+  const windowed = await info();
+
+  // 61a. The header button: the game view alone fills the page, and the game goes on.
+  await click(windowed.headerButton.x, windowed.headerButton.y);
+  await sleep(500);
+  const full = { ...(await info()), mode: await json('__gm.state.mode') };
+  check(
+    'the header button puts the running game view alone into fullscreen',
+    windowed.view.y > 0 &&
+      full.on &&
+      full.document &&
+      full.headerButton === null &&
+      full.view.x === 0 &&
+      full.view.y === 0 &&
+      full.view.w === size.w &&
+      full.view.h === size.h &&
+      full.mode === 'play',
+    JSON.stringify({ size, windowed, full }),
+  );
+  await shot('61-fullscreen');
+
+  // 61b. The corner button leaves it, and the view is back under its header, as big as before.
+  if (full.corner) await click(full.corner.x, full.corner.y);
+  await sleep(500);
+  const back = await info();
+  check(
+    'the corner button leaves fullscreen and puts the view back in its tab',
+    full.corner !== null &&
+      !back.on &&
+      !back.document &&
+      back.headerButton !== null &&
+      JSON.stringify(back.view) === JSON.stringify(windowed.view),
+    JSON.stringify({ corner: full.corner, back }),
+  );
+
+  // 61c. Stop goes back to the scene tab, which ends fullscreen too.
+  await click(back.headerButton.x, back.headerButton.y);
+  await sleep(500);
+  const again = await info();
+  await stop();
+  await sleep(300);
+  const stopped = await info();
+  check(
+    'stopping the game from fullscreen ends fullscreen',
+    again.on && !stopped.on && !stopped.document,
+    JSON.stringify({ again: again.on, stopped }),
+  );
+  check('fullscreen threw nothing', exceptions().length === 0, exceptions().join(' | '));
+}

tools/e2e/index.mjs

@@ -63,6 +63,7 @@ import { objectReferences } from './57-object-references.mjs';
 import { clipAreas } from './58-clip-areas.mjs';
 import { whilePlaying } from './59-while-playing.mjs';
 import { release } from './60-release.mjs';
+import { fullscreen } from './61-fullscreen.mjs';
 
 export const STEPS = [
   hierarchy,
@@ -125,4 +126,5 @@ export const STEPS = [
   clipAreas,
   whilePlaying,
   release,
+  fullscreen,
 ];