fix: add an exit control to fullscreen cell output

[kirangadhave]

📝 Summary

Fullscreen paints the output element only, and the fullscreen and expand buttons sit outside it in the cell gutter. A fullscreen output therefore shows no control at all. Browsers hide this with their own exit overlay and Escape handling, but embedded hosts do not. In JCEF, which backs the JetBrains plugin, no overlay appears and Escape does nothing, so the only way back to the notebook is to clear the cell output.

Render an exit button inside the fullscreen element, and exit on Escape while an output is fullscreen. A local build in PyCharm confirms that the Escape handler works, so JCEF delivers the key and simply never acts on it. This removes the need for a keyboard handler on the plugin side.

Closes marimo-team/jetbrains-marimo#108
Closes MO-7561

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Project	Deployment	Actions	Updated
marimo-docs	Ready	Preview	Sep 9, 2026 7:17pm UTC

[github-actions]

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[Copilot]

🟡 Changes recommended

The new tests override document fullscreen properties without restoring them, which can leak mocked behavior into other test files and cause flaky failures.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds an in-output “Exit fullscreen” control for cell outputs and handles Escape to exit fullscreen, addressing embedded hosts (e.g., JCEF in JetBrains IDEs) that don’t provide browser-native fullscreen exit UI/behavior.

Changes:

• Add an Escape key handler while an output element is fullscreen and render an exit button inside the fullscreen-painted output element.
• Introduce an exitFullscreen() helper that logs a warning if exiting fullscreen fails.
• Add unit tests covering button visibility and exiting fullscreen via click/Escape.

File summaries

File	Description
frontend/src/components/editor/Output.tsx	Adds a fullscreen “exit” button inside the output element and a scoped Escape handler to exit fullscreen.
frontend/src/components/editor/tests/Output.test.tsx	Adds tests verifying the exit button appears only in fullscreen and that click/Escape trigger document.exitFullscreen().

Review details

Suppressed comments (1)

frontend/src/components/editor/tests/Output.test.tsx:177

• This suite overrides document.fullscreenElement and document.exitFullscreen via Object.defineProperty(...) but never restores them, which can leak mocked behavior into other test files (the global test setup only calls vi.clearAllMocks(), which won’t revert property descriptors). Capture the original descriptors and restore them in afterAll.

describe("OutputArea fullscreen exit control", () => {
  let fullscreenElement: Element | null = null;
  const exitFullscreen = vi.fn(() => Promise.resolve());

  beforeEach(() => {
    fullscreenElement = null;
    exitFullscreen.mockClear();
    Object.defineProperty(document, "fullscreenElement", {
      configurable: true,
      get: () => fullscreenElement,
    });
    Object.defineProperty(document, "exitFullscreen", {
      configurable: true,
      value: exitFullscreen,
    });
  });

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Lite

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[cubic-dev-ai]

All reported issues were addressed

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[github-actions]

Coverage Report for ./frontend

Status	Category	Percentage	Covered / Total
🔵	Lines	57.01%	21527 / 37760
🔵	Statements	56.94%	21904 / 38465
🔵	Functions	50.14%	4858 / 9688
🔵	Branches	50.09%	11074 / 22108

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
frontend/src/components/editor/Output.tsx	59.3%	52.22%	46.66%	59.3%	96, 105, 135-136, 167-171, 178-244, 266-337, 378, 417, 444, 460-481
frontend/src/components/ui/fullscreen.tsx	54.68%	45.83%	62.5%	54.68%	25, 82-101, 111, 135-154, 162, 179-196
frontend/src/hooks/useEventListener.ts	100%	100%	100%	100%

Generated in workflow #21223 for commit b625d05 by the Vitest Coverage Report Action

[mscolnick]

we should have a useEventListener(document, () …) that may DRY this up only slightly