Show on: "Active screen" isn't working.

[Andrew-Helmer]

Describe the bug

Show on: "Active screen" doesn't seem to be recognizing when my active screen changes. It always shows on the same screen, regardless of which screen I am working on.

Screenshots / video

I can't record both displays so it's hard to show. But in this video, I first show AltTab working on the current Active Screen, say Monitor #1. Then I move AltTab to my other monitor, Monitor #2, which should change the Active Screen, but when I use it, it shows up on the same screen. Then I select a different window on Monitor #2, start typing into the window on Monitor #2 (just to make sure the keyboard is active), then activate AltTab, and it still shows up on Monitor #1.

Steps to reproduce the bug

In AltTab version 6.24.0, macOS Big Sur 11.5.2, with two monitors connected to the Mac (not mirrored). I also have "Displays have separate Spaces" unchecked in the Mission Control System Preferences. Not sure if that's important.

1. In AltTab preferences > Appearance, set "Show on:" to "Active screen".
2. Initiate Shortcut 1 (for me this is with Cmd + Tab, by default it would be Alt + Tab), to see which screen AltTab shows up on.
3. Open a window on the other screen, select that window and type something to make sure it's activate.
4. Initiate Shortcut 1 again.

For me, AltTab still shows up on the first screen, even though that is no longer the active screen. I would expect it to show up on the other screen.

screen_recording_small.mp4

[lwouis]

I was able to reproduce the bug. I think it only happens because Displays have separate Spaces is unchecked. When unchecked, multiple screens become one extended "screen".

Look at the very straightforward source code:

We are calling NSScreen.main, which documentation from Apple says:

Returns the screen object containing the window with the keyboard focus.

I found this StackOverflow explaining the history, and why the API is incorrect now.

[lwouis]

I re-implemented finding the key-window manually instead of using Apple's bogus NSScreen.main API. I tested on the 2 use-cases that were an issue, and it works correctly for me now, regardless of the Displays have separate Spaces checkbox. As a reminder, the 2 use-cases are:

• if the active screen shows a fullscreen app, it always returns screens[0]
• if NSScreen.screensHaveSeparateSpaces == false, and key window is on another screen than screens[0], it still returns screens[0]

The workaround will ship in the next release of AltTab 👍

[Andrew-Helmer]

This is great, thank you so much!!