Fix browser pane stuck in HTML fullscreen (#6442) (#6451)

* Fix browser pane stuck in HTML fullscreen (#6442)

Guest content in a browser pane could enter HTML fullscreen but not
exit it: requestFullscreen() resized the host BrowserWindow into native
fullscreen, and exitFullscreen() had nothing to restore, leaving the
pane stuck.

Set the webview's disableHtmlFullscreenWindowResize preference so HTML
fullscreen is contained to the <webview> element. Exit then works and
fullscreenchange fires as guests expect.

* Apply browser guest fullscreen policy consistently

Co-authored-by: Orca <help@stably.ai>

---------

Co-authored-by: Wolfgang Schoenberger <221313372+wolfiesch@users.noreply.github.com>
Co-authored-by: Jinwoo-H <jinwoo0825@gmail.com>
Co-authored-by: Orca <help@stably.ai>

src/main/browser/offscreen-browser-backend.ts

@@ -1,6 +1,7 @@
 import { randomUUID } from 'crypto'
 import { BrowserWindow } from 'electron'
 import { ORCA_BROWSER_PARTITION } from '../../shared/constants'
+import { ORCA_BROWSER_GUEST_WEB_PREFERENCES } from '../../shared/browser-guest-web-preferences'
 import type { BrowserBackend, BrowserBackendCreateTab } from './browser-backend'
 import type { BrowserManager } from './browser-manager'
 import { browserSessionRegistry } from './browser-session-registry'
@@ -35,6 +36,9 @@ export class OffscreenBrowserBackend implements BrowserBackend {
       width: DEFAULT_VIEWPORT_WIDTH,
       height: DEFAULT_VIEWPORT_HEIGHT,
       webPreferences: {
+        // Why: offscreen pages are the SSH/headless browser backend; keep their
+        // HTML fullscreen behavior aligned with desktop <webview> guests.
+        ...ORCA_BROWSER_GUEST_WEB_PREFERENCES,
         partition,
         sandbox: true,
         contextIsolation: true,

src/main/browser/offscreen-browser-backend.web-preferences.test.ts

@@ -0,0 +1,27 @@
+import { readFileSync } from 'fs'
+import { resolve } from 'path'
+import { describe, expect, it } from 'vitest'
+
+const OFFSCREEN_BACKEND_SOURCE = resolve(__dirname, 'offscreen-browser-backend.ts')
+
+function sourceBetween(source: string, start: string, end: string): string {
+  const startIndex = source.indexOf(start)
+  const endIndex = source.indexOf(end, startIndex + start.length)
+
+  expect(startIndex).toBeGreaterThanOrEqual(0)
+  expect(endIndex).toBeGreaterThan(startIndex)
+
+  return source.slice(startIndex, endIndex)
+}
+
+describe('OffscreenBrowserBackend web preferences', () => {
+  it('uses the shared browser guest fullscreen policy', () => {
+    const source = readFileSync(OFFSCREEN_BACKEND_SOURCE, 'utf8')
+    const webPreferencesBlock = sourceBetween(source, 'webPreferences: {', 'partition,')
+
+    expect(source).toContain(
+      "import { ORCA_BROWSER_GUEST_WEB_PREFERENCES } from '../../shared/browser-guest-web-preferences'"
+    )
+    expect(webPreferencesBlock).toContain('...ORCA_BROWSER_GUEST_WEB_PREFERENCES')
+  })
+})

src/main/window/createMainWindow.test.ts

@@ -225,6 +225,11 @@ describe('createMainWindow', () => {
       { src: 'data:text/html,' } as never
     )
     expect(allowBlankEvent.preventDefault).not.toHaveBeenCalled()
+    expect(allowBlankPrefs).toMatchObject({
+      disableHtmlFullscreenWindowResize: true,
+      partition: 'persist:orca-browser',
+      sandbox: true
+    })
 
     const denyInlineHtmlEvent = { preventDefault: vi.fn() }
     windowHandlers['will-attach-webview'](

src/main/window/createMainWindow.ts

@@ -20,6 +20,7 @@ import {
   normalizeBrowserNavigationUrl,
   normalizeExternalBrowserUrl
 } from '../../shared/browser-url'
+import { ORCA_BROWSER_GUEST_WEB_PREFERENCES } from '../../shared/browser-guest-web-preferences'
 import { isCrashReportReason } from '../../shared/crash-reporting'
 import {
   getWindowShortcutActionId,
@@ -485,6 +486,9 @@ export function createMainWindow(
     webPreferences.allowRunningInsecureContent = false
     webPreferences.contextIsolation = true
     webPreferences.sandbox = true
+    // Why: keep renderer-created webviews aligned with the browser guest policy
+    // even if the host markup omits or misspells a preference.
+    Object.assign(webPreferences, ORCA_BROWSER_GUEST_WEB_PREFERENCES)
     // Why: preserve the registry-validated partition instead of forcing the
     // legacy constant. This lets imported/isolated session profiles use their
     // own cookie/storage partition while keeping all other hardening intact.

src/renderer/src/components/browser-pane/BrowserPane.tsx

@@ -77,6 +77,7 @@ import {
   browserViewportPresetToOverride,
   getBrowserViewportPreset
 } from '../../../../shared/browser-viewport-presets'
+import { ORCA_BROWSER_GUEST_WEB_PREFERENCES_ATTRIBUTE } from '../../../../shared/browser-guest-web-preferences'
 import { rememberLiveBrowserUrl } from './browser-runtime'
 import {
   destroyPersistentWebview,
@@ -3612,6 +3613,16 @@ function BrowserPagePane({
       webview = document.createElement('webview') as Electron.WebviewTag
       webview.setAttribute('partition', webviewPartition)
       webview.setAttribute('allowpopups', '')
+      // Why: keep HTML fullscreen contained to the <webview> element instead of
+      // letting guest content resize the host BrowserWindow into native macOS
+      // fullscreen. Without this, requestFullscreen() resizes the OS window but
+      // exitFullscreen() has nothing to restore, leaving the pane stuck
+      // fullscreen (issue #6442). Containing fullscreen to the element makes
+      // exit reliable and fires fullscreenchange as guests expect.
+      // Why: the key must be camelCase — Electron's <webview> webpreferences
+      // parser spreads keys verbatim into WebPreferences, so a lowercase key is
+      // silently ignored.
+      webview.setAttribute('webpreferences', ORCA_BROWSER_GUEST_WEB_PREFERENCES_ATTRIBUTE)
       webview.style.display = 'flex'
       webview.style.flex = '1'
       webview.style.width = '100%'

src/renderer/src/components/browser-pane/BrowserPane.webview-preferences.test.ts

@@ -0,0 +1,38 @@
+import { readFileSync } from 'fs'
+import { resolve } from 'path'
+import { describe, expect, it } from 'vitest'
+
+const BROWSER_PANE_SOURCE = resolve(__dirname, 'BrowserPane.tsx')
+
+function browserPaneSource(): string {
+  return readFileSync(BROWSER_PANE_SOURCE, 'utf8')
+}
+
+function sourceBetween(source: string, start: string, end: string): string {
+  const startIndex = source.indexOf(start)
+  const endIndex = source.indexOf(end, startIndex + start.length)
+
+  expect(startIndex).toBeGreaterThanOrEqual(0)
+  expect(endIndex).toBeGreaterThan(startIndex)
+
+  return source.slice(startIndex, endIndex)
+}
+
+describe('BrowserPane webview preferences', () => {
+  it('keeps HTML fullscreen contained inside the browser pane webview', () => {
+    const source = browserPaneSource()
+    const creationBlock = sourceBetween(
+      source,
+      "webview = document.createElement('webview')",
+      'registerPersistentWebview'
+    )
+
+    expect(source).toContain(
+      "import { ORCA_BROWSER_GUEST_WEB_PREFERENCES_ATTRIBUTE } from '../../../../shared/browser-guest-web-preferences'"
+    )
+    expect(creationBlock).toContain(
+      "webview.setAttribute('webpreferences', ORCA_BROWSER_GUEST_WEB_PREFERENCES_ATTRIBUTE)"
+    )
+    expect(creationBlock).not.toContain('disablehtmlfullscreenwindowresize')
+  })
+})

src/shared/browser-guest-web-preferences.ts

@@ -0,0 +1,5 @@
+export const ORCA_BROWSER_GUEST_WEB_PREFERENCES = {
+  disableHtmlFullscreenWindowResize: true
+} as const
+
+export const ORCA_BROWSER_GUEST_WEB_PREFERENCES_ATTRIBUTE = 'disableHtmlFullscreenWindowResize=true'