Window input focus sometimes failing after showing&activating (Windows 11)

[genejo]

Hi there,

Context: showing & activating an Avalonia window with a global hotkey after previously hiding it or switching focus away from it. The window has a textbox which should start capturing input.

Good part: when pressing the hotkey (handled via SharpHook) the Avalonia window is always brought to foreground. I'm using this code snippet:

win.Show();
win.Activate();
win.Topmost = true;
win.Topmost = false;

Bad part: However in certain instances the input focus remains on whatever window/control was active at the time of pressing the hotkey.

Scenario for the issue to occur:

• run the executable directly (even as amin)
• alt-tab away from the window, or click away
• focus on something (e.g. Calculator app, windows search, windows explorer...)
• press hotkey to reactivate the Avaolonia window
• => window appears in the foreground, but you can tell by how the title bar looks it's not in focus
• => typing something is not captured by the Avalonia window, but by whatever was in focus (Calculator, windows search, explorer...)

The issue doesn't occur when:

• running the executable directly as above, but purposefully hiding the window (win.Hide() e.g. when Esc is pressed) instead of clicking/alt-tabbing away
• launching the application from the IDE (tried Rider & Visual Studio)
• using macos

I also tried using native calls like the ones below, but nothing seems to help with the scenario presented. Would anyone happen to know how to programmatically show & activate a window and have it capture input under any circumstance?

[DllImport("user32.dll")]
private static extern bool SetForegroundWindow(IntPtr hWnd);

[DllImport("user32.dll")]
private static extern IntPtr GetForegroundWindow();

[DllImport("user32.dll")]
private static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

[DllImport("kernel32.dll")]
private static extern uint GetCurrentThreadId();

[DllImport("user32.dll")]
private static extern bool AttachThreadInput(uint idAttach, uint idAttachTo, bool fAttach);

[LaurentInSeattle]

Your app is willing to "steal" the focus, which is not always "desirable". So, showing is not doing it by default.

Have you tried something like that? (in Ctor of main window)

    this.Activated += (s, e) => this.Focus(); 

=> Not tested with Avalonia, but was working in WPF years ago...

[genejo]

Thanks Lawrent. Sadly it didn't work, but it was worth a shot.

Usually it's indeed not good UX, but in this case the application is meant to act like PowerToys search / Everything (voidtools) / Listary / Spotlight etc.. There you expect the focus to be grabbed and just start searching.

[LaurentInSeattle]

Maybe... maybe... it's not working because focusing the window is not enough in Avalonia..
Focusing a TextBox data entry field would do it ?

[genejo]

Sadly I’ve been doing this all along to no avail. The design is indeed so that the textbox grabs focus when opened via hotkey no matter if the focus was previously somewhere else.

I just noticed that setting the window state to WindowState.Maximized also works when running from the IDE (debug / release - doesn’t matter), but not when running the managed executable directly. Whatever it is, it seems to make the a window’s properties / calls not result in the expected behavior.

[genejo]

Oh wow, this is not an Avalonia issue - I was barking at the wrong tree. It's a known issue for Windows applications in general. I tried coding this feature directly using Win 32 API and encountered the same issue.

Microsoft PowerToys Command Palette (former Run) solves it by hack-sending some mouse input before bringing the window to foreground.

Pasting below some Win 32 API code that does this and works. After DllImport-ing all necessary functions and creating the needed structures for .NET things worked for hwnd = win.TryGetPlatformHandle()

void ForceToForeground(HWND hwnd) {
    // Restore if minimized
    if (IsIconic(hwnd)) {
        ShowWindow(hwnd, SW_RESTORE);
    }
    
    INPUT inputs[1] = {};
    inputs[0].type = INPUT_MOUSE;
    SendInput(1, inputs, sizeof(INPUT));
    
    // Now SetForegroundWindow will work
    SetForegroundWindow(hwnd);
}