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 feature request that matches the one I want to file, without success.

Electron Version

12.0.9
13.0.1
14.1.0
15.1.1

What operating system are you using?

Other Linux

Operating System Version

NixOS 21.05

What arch are you using?

x64

Last Known Working Electron version

12.0.0-beta.20

Expected Behavior

shell.openExternal("https://electronjs.org/") opens a browser tab at https://electronjs.org/. (My browser is Firefox on Wayland with MOZ_ENABLE_WAYLAND=1, and has other tabs already open.)

Actual Behavior

Firefox shows this error and does not open a tab:

“Firefox is already running, but is not responding. To use Firefox, you must first close the existing Firefox process, restart your device, or use a different profile.”

Testcase Gist URL

https://gist.github.com/31ec2165f4aa806536e11d7d99d1e26f

I bisected this to v12.0.0-beta.20...v12.0.0-beta.21 (9faf235...5dbb635).

The difference between v12.0.0-beta.20’s working invocation of xdg-open and v12.0.0-beta.21’s failing invocation is that the latter has GDK_BACKEND=x11 in the environment. I confirmed that this is responsible for the failure with manual invocations of

xdg-open https://electronjs.org/  # works
env GDK_BACKEND=x11 xdg-open https://electronjs.org/  # fails

I don’t know if Electron or Chromium need to set GDK_BACKEND=x11 for their own purposes, but it definitely should not be propagated to subprocesses such as xdg-open.