[Bug]: setWindowOpenHandler results in incorrect dark mode background color for text/plain content

[jeremyspiegel]

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a bug report that matches the one I want to file, without success.

Electron Version

Electron 21.3.1, 22.0.0, and the latest 24.0.0-nightly.20221201

What operating system are you using?

macOS 13 and Windows 11

What arch are you using?

arm64 (including Apple Silicon)

Last Known Working Electron version

n/a

Expected Behavior

When the system is in dark mode, and a popup is opened via window.open to a URL returning content of type text/plain, the resulting popup window should have a black background with white text. This happens correctly unless mainWindow.webContents.setWindowOpenHandler is called.

See https://www.loom.com/share/4af414156762410e994b5e2a56d997c7 for the correct behavior when mainWindow.webContents.setWindowOpenHandler is commented out.

Actual Behavior

With the call to mainWindow.webContents.setWindowOpenHandler uncommented, the popup window incorrectly has white text with a white background. See https://www.loom.com/share/15aadf785f3740c5b8f07239ea1e46ed for the actual behavior.

Testcase Gist URL

https://gist.github.com/36925a2377d0b8c7c67abd9816c2f411

[jeremyspiegel]

I think this is related to #28054. cc @MarshallOfSound

[dsanders11]

Text in the opened window first turned white starting in 19.0.0-nightly.20220325.

[dsanders11]

I'm investigating root cause, but in the mean time, this is a workaround which causes the behavior to be the same whether setWindowOpenHandler is set or not:

mainWindow.webContents.setWindowOpenHandler(() => ({action: 'allow', overrideBrowserWindowOptions: { backgroundColor: '000000' }}))

The backgroundColor value doesn't matter, as it will be immediately replaced by the expected background color for dark mode.