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How to keep window visible at all times, but not force it to be on top

I'm creating a "desktop gadget" of sorts, I've disabled manual minimizing of the window, but now there is another problem: the system can still hide the window if the user presses Windows+D, for example.
When hidden that way, no usual minimize/resize/visibility events are fired.
I want to do something almost like TopMost, but without forcing the window order.
Maybe it's possible to install a global shortcut event using win32 API, and briefly set TopMost to true, but that sounds very hackish.
I found one solution, but it does not seem to work on Windows 10: Keeping window visible through "Show Desktop"/Win+D
The other common option, which would be writing an actual desktop gadget, is not possible on Windows 10, given their deprecation.
Are there any other methods to keep a window visible (but not on top of the screen) at all moments?

This function is working for me:
BOOL FixShowDesktop(HWND hWnd)
{
HWND hWndTmp = FindWindowEx(NULL, NULL, L"Progman", NULL);
if (hWndTmp)
{
hWndTmp = FindWindowEx(hWndTmp, NULL, L"SHELLDLL_DefView", NULL);
if (hWndTmp)
{
SetWindowLongPtr(hWnd, -8, (LONG_PTR)hWndTmp);
return TRUE;
}
}
return FALSE;
}
Note, this code is a bit better then from Keeping window visible through "Show Desktop"/Win+D because the window can be overflowed by other windows (like any other window). Using SetParent places window under all other windows.

ShowInTaskbar not working reliably in WPF

I have a modal window in WPF and for this window ShowInTaskbar is set to true but application icon is not showing in taskbar every time for this model window. Sometimes the icon shows up in taskbar and sometimes it does not. But the requirement is application icon should always be visible in the taskbar when this modal window (using ShowDialog) is launched.
window Style is set as : ThreeDBorderWindow
Code to show modal window is :
winIHelper = new WindowInteropHelper(_shell);
_shell.SizeToContent = SizeToContent.WidthAndHeight;
winIHelper.Owner = parentHandle;
_shell.ShowInTaskbar = true;
_shell.Activate();
_shell.ShowDialog();

I had a similar case where ShowInTaskbar was not working correctly when a different window (Splash screen in my case) was shown without setting any Owner.
So, settings the Owner property of the Other window - solved my case.

WPF MessageBox not waiting for result [WPF NotifyIcon]

I am using WPF NotifyIcon to create a System Tray service. When I show a messagebox, it shows up for half a second and then disappears immediately without waiting for input.
This kind of situation has happened before, and the usual advice is to use an overload which accepts a Window parameter. However, being a System Tray service, there is no window to use as a parent, and null is not accepted in its place.
Is there any way to make the MessageBox wait for user input short of creating a custom MessageBox window myself?

You don't need to create a proxy window for this. Just add MessageBoxOptions.DefaultDesktopOnly to your message box and it will fire on your desktop without disappearing.
Example
MessageBox.Show("My Message", "Title", MessageBoxButton.OK,
MessageBoxImage.Information, MessageBoxResult.OK,
MessageBoxOptions.DefaultDesktopOnly);

According to the answer here, a workaround is to actually open an invisible window and use that as the parent of the MessageBox:
Window window = new Window()
{
Visibility = Visibility.Hidden,
// Just hiding the window is not sufficient, as it still temporarily pops up the first time. Therefore, make it transparent.
AllowsTransparency = true,
Background = System.Windows.Media.Brushes.Transparent,
WindowStyle = WindowStyle.None,
ShowInTaskbar = false
};
window.Show();
...then open the MessageBox with the appropriate parameter:
MessageBox.Show(window, "Titie", "Text");
...and don't forget to close the window when you're done (possibly on application exit):
window.close();
I tried this and it works well. It's undesirable to have to open an extra window, but it's better than making your own messagebox window just for the sake of making this work.

RegisterHotKey not working with invisible forms (c#)

I'm trying to put an icon in the system tray and then give it a global keyboard shortcut to carry out a function.
I'm using RegisterHotKey to set the global keyboard shortcut, and it works if the main form associated with the icon is visible. But if the form is invisible then the WndProc method is never invoked.
Any ideas?
Edit:
What I mean by "hidden" is that the following is added to the main form:
protected override void OnLoad(EventArgs e)
{
hotKey = new GlobalHotkey(GlobalHotkey.WIN, Keys.T, this);
bool registered = hotKey.Register();
Visible = false;
ShowInTaskbar = false;
base.OnLoad(e);
}
"registered" is showing as "true", and the shortcut key works fine if I leave out the "Visible = false;" and the "ShowInTaskbar = false;".

The problem is that setting ShowInTaskbar to false changes the window handle, which means that the hwnd passed to RegisterHotkey is no longer valid.
Registering the hotkey after setting ShowInTaskBar works fine.

Winforms works around a pretty draconian restriction in the winapi. Some properties of a window can only be specified when a window is created and can't be changed later. Or in other words, they are specified in the native CreateWindowEx() call.
It works around it by calling CreateWindowEx() again. Or in other words, destroy the existing window and create it again. That's a nifty trick but it does have some side effects. You can see a wee bit of flicker for example when the new window paints itself. Some bigger side effects are visible on for example a TreeView. All the nodes collapse when it gets recreated. Hard to avoid, there is just too much state associated with the original window. For a Form, the ShowInTaskbar property is one such property. But also RightToLeft, FormBorderStyle, ControlBox, etcetera.
The most relevant side-effect is the one you are running into. Recreating the window always changes the Handle property, inevitably. And that goes wrong when you use RegisterHotKey(), or a library that uses it, that winapi call uses the window handle. So when Winforms destroys that window there will never again be a callback.
It is easy to fix, you are just using the wrong event handler. Make the call in an override for the OnHandleCreated method instead. It re-runs when the window gets re-created. Yet another easy fix, but not nearly as reliable, is to only set properties like ShowInTaskbar in the constructor.

WPF owner window on top of child window

Is it possible for Owner window in WPF be on top of Child window when you click on it while Owner window is below Child window?
here is example how I call child window:
Window2 window = new Window2();
window.Owner = this;
window.Show();
Parent/Owner window will always be under child window.

To get the behavior you want, you don't want to set the Owner on either window.
You, of course will have to handle the logic yourself when closing either of the windows to close your imaginary "child" window.
There may be some other logic you'll have to implement related to minimizing, maximizing, etc.

Many of the answers on this page involve nulling-out the Window.Owner property for some or all of the (non-MainWindow) windows in your System.Windows.Application. While this is a simple and easy fix that does indeed, in isolation, fix the issue of Window overlap, unfortunately it also inhibits a lot of useful application-wide functionality that WPF seems otherwise eager to provide in the areas of:
Application acti­vation/deactivation (via mouse-click, desktop Alt-Tab switching, etc...),
correct observance of the Application.​ShutdownMode property, and generally,
orderly cleanup, resource disposal, and exit of your Application upon shutdown.
It is possible fix the Window overlap issue while still preserving these system-wide WPF features by instead designating a special invisible window instance as your Application.MainWindow.
Modify your application so that the first Window it creates--which is the Window that gets assigned to Application.MainWindow--is a special dummy Window that is then made invisible by setting its Visibility to Visibility.Hidden or calling Window.Hide(). This will not hide its owned windows. Then, ensure that your desired "main" window containing your true content, plus all the other windows, owned by this invisible window.
Once hidden, the dummy Window will not show in the Windows 10 taskbar. You can set the Window.ShowInTaskbar property on whichever of the visible windows you deem appropriate to simulate apparent special designation, as required.
This approach allows any of the visible windows in your Application to be on top of the others, while still preserving WPF features and behaviors for system-wide app activation. For example, when the Application is activated (by clicking on any one of the windows, or via Alt-tab), all of the application's windows are together brought above any other desktop app windows, while still preserving the most recent "in-app" Z-order. WPF shutdown functionality is also preserved, including correct observation of the Application.ShutdownMode logic in accordance with the invisible MainWindow (or all the others) being closed.

I ran into a similar situation. I solved this by simply removing the owner after showing the window.
Window2 window = new Window2();
window.Owner = this;
window.Show();
window.Owner = null;
Edit:
Someone replied to this, and while looking at it, I decided I wanted to make an extension method.
public static void ShowAsIfChildOf(this Window childWindow, Window parentWindow)
{
childWindow.Owner = parentWindow;
childWindow.Show();
childWindow.Owner = null;
}

Please note that the solution mentioned by Licht
Window2 window = new Window2();
window.Owner = this;
window.Show();
window.Owner = null;
seems to me to be the same as
Window2 window = new Window2();
window.Show();
i.e., as if no ownership relationship has been set, i.e., when you close the owner window the owned windows do not close, etc., and may not be a solution when one would wish to have all of the ownership relationship features except "An owner window can never cover an owned window."
Once this relationship is established, the following behaviours are exhibited:
If an owner window is minimized, all its owned windows are minimized as well.
If an owned window is minimized, its owner is not minimized.
If an owner window is maximized, both the owner window and its owned windows are restored.
An owner window can never cover an owned window.
Owned windows that were not opened using ShowDialog are not modal. The user can still interact with the owner window.
If you close an owner window, its owned windows are also closed.
The best solution here looks to me to be the one with hidden main dummy window described by Glenn Slayden, at the link below, though it would be nice if there was a simpler one.
https://stackoverflow.com/a/66110288/19683309

Don't set Owner for child window, then in MainWindow handle OnClosing event like this:
private void MainWindow_OnClosing(object? sender, CancelEventArgs e)
{
foreach (var window in Application.Current.Windows)
{
if (window is Window appWindow)
{
if(appWindow.Equals(Application.Current.MainWindow))
continue;
appWindow.Close();
}
}
}