Electron Releases

Description of Change

fixes: #48311

• stop overriding the private _cornerMask selector in ElectronNSWindow
• remove the cornerMask plumbing that applied a custom mask image to vibrant views
• rely on AppKit’s default shadow rendering, which fixes the WindowServer GPU spike on macOS 26 Tahoe when shadows are enabled

Rationale:

If AppKit uses method implementation identity to decide whether the window mask is static, then a subclass override (even if it calls super) will change that identity and force the compositor to treat the mask as dynamic.

Method-IMP sentinel check

AppKit asks: “is _cornerMask implemented by the standard theme frame?” via class_getMethodImplementation / method_getImplementation.
If yes → treat masks as canonical and use a shared cache keyed by class/selector;
if no → mark mask as custom and re-render per-window. → persistent high GPU load

Backwards-compat concerns:

I see no reason to override _cornerMask as the corner radius masking is already covered by NSVisualEffectView setMaskImage, rendering NO visual difference without _cornerMask override + vibrancy

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant API documentation, tutorials, and examples are updated and follow the documentation style guide
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed excessive WindowServer GPU usage on macOS Tahoe 26.