macOS Client 4.12.0 mixes dark and light themes

[maiksd]

I'm running a dark-themed application in a light-themed macOS. After updating the client to 4.12.0, the outer left and top borders of the application follow the OS setting instead of the per-application override that can be set in "Accessibility & appearance". See:

[abhnish]

Hi @maiksd
I’d like to work on this issue if it’s okay.

[KevLehman]

@jeanfbrito maybe this one should be on the electron repo?

[abhnish]

Hi @KevLehman , I’ve been investigating this issue on macOS and wanted to share some findings.

After testing multiple approaches, I confirmed that when using titleBarStyle: 'hidden', the outer window frame (traffic-light region and border) does not fully respect the in-app theme override when the system appearance differs.

What I tested so far:

Dynamically updating nativeTheme.themeSource

Forcing BrowserWindow.setBackgroundColor

Toggling vibrancy

Switching between hidden and hiddenInset

Recreating the BrowserWindow on theme change

While these approaches partially update the content area, the native macOS window frame still follows the system NSAppearance in certain cases.

From what I understand, Electron does not fully expose APIs to override the underlying NSWindow appearance when titleBarStyle: 'hidden' is used. The only reliable way I found to make the frame fully respect the in-app theme is by directly setting the window appearance at the macOS level (via NSWindow.setAppearance), which would require a small macOS-specific native module.

Before proceeding further, I wanted to ask:

Would a macOS-only native solution be acceptable here, or would maintainers prefer an Electron-only workaround (even if slightly less precise)?

Happy to prepare a PR based on the preferred direction.