fix(wm): notify subscribers on floating window focus change (update the focus index of floating windows)

[JustForFun88]

Issue discovered during testing #1465:

When more than two floating windows are present, switching focus between floating windows does not update the Komorebi bar status - meaning the bar keeps showing the previously focused floating window as active, instead of updating to the new focused window.

Root cause:

We did not notify subscribers about floating window focus changes, because the current focused floating window index in the workspace was not updated on focus change, so has_been_modified didn’t detect a state change.

The PR adds code to update the focused floating window in the current workspace before notifying subscribers. As a result, notifications about floating window focus changes are now correctly sent to all subscribers, and the Komorebi bar updates as expected.

How to reproduce (before fix):

• Open 2+ floating windows.
• Switch focus between them.
• Notice that the Komorebi bar does not reflect the focus change.

bug.mp4

How to test (after fix):

• Repeat the steps above: the Komorebi bar now updates when focus changes between floating windows.

[JustForFun88]

@LGUG2Z I’m a little bit confused. Since we are working with floating windows, this line of code should be enough as it is. However, in the following scenario there is a problem:

• There are three tiling windows.
• I make one of them floating.
• I hover over one of the remaining tiling windows, select it, and also make it floating. It now appears on top of the first floating window.
• I drag this second floating window slightly so the first floating window is visible underneath, and then select that first floating window.
• At this point the call of workspace.floating_windows.focus(idx) should update the focused-window index, but it seems the state isn’t refreshed, because notify_subscribers does not send a message.
• If I then select the second floating window again, everything works as expected and notify_subscribers fires. After that, switching focus between the two floating windows continues to work normally.

example.mp4

However, if I add the following piece of code to update_focused_workspace function, everything works from the start:

let fl_windows = &mut self.focused_workspace_mut()?.floating_windows;
if let Some(idx) = fl_windows.elements().iter().position(|w| w.is_focused()) {
    fl_windows.focus(idx);
}

I don't understand why this happens. Do you have any idea?

[JustForFun88]

This alone is not sufficient. It does not update the indices when the workspace is empty, so it should be used together with workspace.floating_windows.focus(idx) in the WindowManagerEvent::FocusChange(_, window) handler. However, if you remove this code and leave only workspace.floating_windows.focus(idx) in WindowManagerEvent::FocusChange(_, window), it won’t work immediately after making two windows floating one after another (and I don't know why).

[LGUG2Z]

I would like to revisit this and understand if this is still an issue on v0.1.40 that needs addressing; I'll convert this to a draft until we can make a determination and resolve any conflicts