Window "on desktop"

Question

Hello, I've been using Rainlendar for some time and I noticed that it has an option to put the window "on desktop". It's like a bottomMost window (as against topmost).

How could I do this on a WPF app?

Thanks

Answer 1

My answer is in terms of the Win32 API, not specific to WPF (and probably requiring P/Invoke from C#):

Rainlendar has two options:

• "On Desktop", it becomes a child of the Explorer desktop window ("Program Manager"). You could achieve this with the SetParent API.
• "On Bottom" is what you describe - its windows stay at the bottom of the Z-order, just in front of the desktop. It's easy enough to put them there to begin with (see SetWindowPos) - the trick is to stop them coming to the front when clicked. I would suggest handling the WM_WINDOWPOSCHANGING message.

Answer 2

This is what I used so the window is always "on bottom":

   using System;
    using System.Runtime.InteropServices;
    using System.Windows;
    using System.Windows.Interop;

...

[DllImport("user32.dll")]
static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X,
   int Y, int cx, int cy, uint uFlags);

const UInt32 SWP_NOSIZE = 0x0001;
const UInt32 SWP_NOMOVE = 0x0002;
const UInt32 SWP_NOACTIVATE = 0x0010;

static readonly IntPtr HWND_BOTTOM = new IntPtr(1);

public static void SetBottom(Window window)
{
    IntPtr hWnd = new WindowInteropHelper(window).Handle;
    SetWindowPos(hWnd, HWND_BOTTOM, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE | SWP_NOACTIVATE);
}

Answer 3

The OnDesktop version that Im using:

[DllImport("user32.dll")]
static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);
[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

public static void SetOnDesktop(Window window)
{
    IntPtr hWnd = new WindowInteropHelper(window).Handle;         
    IntPtr hWndProgMan = FindWindow("Progman", "Program Manager");
    SetParent(hWnd, hWndProgMan);
}

I was having some trouble finding the Program Manager window, but Kimmo, the creator from Rainlendar gave me a link to the code:

http://www.ipi.fi/~rainy/legacy.html

If anybody needs more detail just look in library/rainwindow.cpp for the function SetWindowZPos.

Answer 4

Warning The accepted answer suggests that you call SetParent to create a child of the Desktop. If you do this, you cause the Win32 Window Manager to synchronize the input queue of the Desktop to your child window, this is a bad thing - Raymond Chen explains why. Basically, if your window hangs or blocks (say with a MessageBox) you will lock up your desktop.