fix: allow null viewport to disable viewport emulation

[kitiho]

Problem

Passing viewport: null to launchPersistentContext() has no effect — the browser always launches with DEFAULT_VIEWPORT (1920×947) because the ?? operator treats null the same as undefined.

Root cause

viewport: options.viewport ?? DEFAULT_VIEWPORT

?? coalesces both null and undefined, so an explicit null (which in Playwright means "disable viewport emulation and let the OS window control the size") is silently replaced by DEFAULT_VIEWPORT.

Fix

Use a strict undefined check so null is passed through to Playwright:

viewport: options.viewport === undefined ? DEFAULT_VIEWPORT : options.viewport,

Also update the viewport type in LaunchContextOptions to accept null:

viewport?: { width: number; height: number } | null;

Why it matters

Desktop apps (e.g. Electron) need the browser content to resize with the window. With viewport: null, Playwright/Chromium uses the actual window dimensions and responds to resize events. Without this fix there is no way to opt out of the fixed 1920×947 default.

[Cloak-HQ]

Thanks for the clean PR, good catch on the ?? vs null behavior.

We confirmed the bug — viewport: null is a valid Playwright API value (disables viewport emulation), and ?? silently swallows it.

One thing: launchPersistentContext at line 171 has the same pattern:

viewport: options.viewport ?? DEFAULT_VIEWPORT,

Happy to merge this as-is and fix it ourselves, or if you'd like to add it to this PR that works too. Up to you.

[kitiho]

Thanks for pointing that out! I've applied the same fix to launchPersistentContext as well — changed ?? to an explicit === undefined check so viewport: null is correctly passed through there too.

[Cloak-HQ]

Thanks for the fix, @kitiho! Merged and shipped.

We also applied the same fix to the Python wrapper (browser.py) in 1060772 — Python's Playwright API uses no_viewport=True instead of viewport=None, so we translate accordingly. You're credited as co-author on that commit.

Added you to the Contributors section in README as well.