focus-follows-mouse focus floating windows even when they're behind a tilling window

[gabsrp2002]

Body

Steps to reproduce:

Open one window in a tiled layout
Open one floating window and put it behind the tilling window (focus the tilling window)
Move your mouse across the tilling window

Expected result:
The tilling window should remain focused (since the mouse is hovering over it only).

Actual result:
The other window behind the tilling window becomes focused.

Additional info
aerospace CLI client version: 0.21.1-Beta cfd4eab
AeroSpace.app server version: 0.21.1-Beta cfd4eab

[sydalwedaie]

Actually I kinda like this behavior. I don't use floating windows that often. The macOS Settings window is among the very few ones. Say I'm reading a guide in the tiled browser which wants me to follow along in Settings. I open it on top of the browser, but it clips part of what I'm reading. With this behavior, I simply move the mouse out of Settings, continue reading what was behind, and come back to Settings by moving the mouse back. Beautiful! I never thought I needed such a behavior!

But I'm sure not everyone likes it. Maybe a second option can be added to disable this specific behavior.

[adamzenith]

I made and tested one potential fix for this locally. It happens because the focused window when focusFollowMouse is enabled looks only at the coordinates of the windows Rect, but doesn't worry about which windows are on top. It also looks at floating windows before tiled ones, so the floating one will always end up on top.

var window: Window? = nil
for child in workspace.floatingWindowsContainer.mruChildren {
    guard let rect = try await child.getAxRect(.cancellable) else { continue }
    if rect.contains(location) { window = child; break }
}
if window == nil {
    window = location.findWindowRecursively(in: workspace.rootTilingContainer, ...)
}

A fix is to ask the window server which window is actually on top. CGWindowListCopyWindowInfo with .optionOnScreenOnly returns on-screen windows front-to-back; We can simply pick the first one here that fits within the mouse coordinates.

This is how i implemented it:

@MainActor event in
        let location = event.locationInWindow.withYAxisFlipped
        focusFollowsTask?.cancel()
        focusFollowsTask = Task.startUnstructured { @MainActor in
            guard let token: RunSessionGuard = .isServerEnabled else { return }
            try checkCancellation()
            // Ignores macOS menubar dropdown, but, unfortunately, it doesn't ignore non-native menu-like fake windows.
            // todo: It would be cool to somehow reuse isWindowHeuristic logic here
            if await isAxWindowUnderMouse(location) == false { return }
            try checkCancellation()
            let workspace = location.monitorApproximation.activeWorkspace
            var window: Window? = nil
            for child in workspace.floatingWindowsContainer.mruChildren {
                try checkCancellation()
                guard let child = child as? Window else { continue }
                guard let rect = try await child.getAxRect(.cancellable) else { continue }
                if rect.contains(location) {
                    window = child
                    break
            var window: Window? = await windowIdsUnderMouse(location) // Front-to-back order
                .lazy
                .compactMap { Window.get(byId: $0) }
                .first { $0.nodeWorkspace == workspace }
            try checkCancellation()
            if window == nil { // The window server didn't help. Fallback to geometry
                for child in workspace.floatingWindowsContainer.mruChildren {
                    try checkCancellation()
                    guard let child = child as? Window else { continue }
                    guard let rect = try await child.getAxRect(.cancellable) else { continue }
                    if rect.contains(location) {
                        window = child
                        break
                    }
                }
            }
            if window == nil {
                window = location.findWindowRecursively(in: workspace.rootTilingContainer, virtual: false, fullscreenCoversAll: true)
            }
            if let window {
                try await runLightSession(.focusFollowsMouse, token) {
                    _ = window.focusWindow()
                    window.nativeFocus()
                }
            }
        }
    }
}

/// Window ids under the mouse, ordered front-to-back, according to the window server.
/// The result contains ids of all on-screen windows, not only the ones that AeroSpace manages
@concurrent
private nonisolated func windowIdsUnderMouse(_ location: CGPoint) async -> [UInt32] {
    // .optionOnScreenOnly guarantees front-to-back order
    let options = CGWindowListOption(arrayLiteral: .excludeDesktopElements, .optionOnScreenOnly)
    guard let cfArray = CGWindowListCopyWindowInfo(options, CGWindowID(0)) as? [CFDictionary] else { return [] }
    var result: [UInt32] = []
    for elem in cfArray {
        let dict = elem as NSDictionary

        guard let _windowId = dict[kCGWindowNumber] else { continue }
        let windowId = ((_windowId as! CFNumber) as NSNumber).uint32Value

        guard let _bounds = dict[kCGWindowBounds] else { continue }
        // kCGWindowBounds is in the flipped (top-left origin) coordinate space, the same as `location`
        guard let bounds = CGRect(dictionaryRepresentation: _bounds as! CFDictionary) else { continue }

        if bounds.contains(location) { result.append(windowId) }
    }
    return result
}

I built and tested it on my machine and it works well, the only caveat being floating windows visible between two tiling windows:

In this case, the floating finder window will open if you hover your mouse over the gap. Technically it is visible, so maybe this is the right behaviour. It also only happens if the mouse is moving slowly enough, if you quickly move it from one side to the other nothing happens.

There could for sure be an option that toggles this behaviour. For my use case, i always have finder and settings set as floating windows, and this behaviour is counterproductive.

[gabsrp2002]

Nice! Did you implement it in a fork? Would you mind sharing a link to it? I'd love to test it out :)

[adamzenith]

I hadn't made one, but i have now! Please let me know if it works as expected :)

https://github.com/adamzenith/AeroSpace/tree/fix-focus-follows-mouse-zorder