How to get the z-order in windows?
You can use the GetTopWindow function to search all child windows of a parent window and return a handle to the child window that is highest in z-order. The GetNextWindow function retrieves a handle to the next or previous window in z-order.
GetTopWindow: http://msdn.microsoft.com/en-us/library/ms633514(VS.85).aspx
GetNextWindow: http://msdn.microsoft.com/en-us/library/ms633509(VS.85).aspx
Nice and terse:
int GetZOrder(IntPtr hWnd)
{
var z = 0;
for (var h = hWnd; h != IntPtr.Zero; h = GetWindow(h, GW.HWNDPREV)) z++;
return z;
}
If you need more reliability:
/// <summary>
/// Gets the z-order for one or more windows atomically with respect to each other. In Windows, smaller z-order is higher. If the window is not top level, the z order is returned as -1.
/// </summary>
int[] GetZOrder(params IntPtr[] hWnds)
{
var z = new int[hWnds.Length];
for (var i = 0; i < hWnds.Length; i++) z[i] = -1;
var index = 0;
var numRemaining = hWnds.Length;
EnumWindows((wnd, param) =>
{
var searchIndex = Array.IndexOf(hWnds, wnd);
if (searchIndex != -1)
{
z[searchIndex] = index;
numRemaining--;
if (numRemaining == 0) return false;
}
index++;
return true;
}, IntPtr.Zero);
return z;
}
(According to the Remarks section on GetWindow
, EnumChildWindows
is safer than calling GetWindow
in a loop because your GetWindow
loop is not atomic to outside changes. According to the Parameters section for EnumChildWindows
, calling with a null parent is equivalent to EnumWindows
.)
Then instead of a separate call to EnumWindows
for each window, which would also be not be atomic and safe from concurrent changes, you send each window you want to compare in a params array so their z-orders can all be retrieved at the same time.
Here is my C# solution: The function returns the zIndex among the siblings of the given HWND, starting at 0 for the lowest zOrder.
using System;
using System.Runtime.InteropServices;
namespace Win32
{
public static class HwndHelper
{
[DllImport("user32.dll")]
private static extern IntPtr GetWindow(IntPtr hWnd, uint uCmd);
public static bool GetWindowZOrder(IntPtr hwnd, out int zOrder)
{
const uint GW_HWNDPREV = 3;
const uint GW_HWNDLAST = 1;
var lowestHwnd = GetWindow(hwnd, GW_HWNDLAST);
var z = 0;
var hwndTmp = lowestHwnd;
while (hwndTmp != IntPtr.Zero)
{
if (hwnd == hwndTmp)
{
zOrder = z;
return true;
}
hwndTmp = GetWindow(hwndTmp, GW_HWNDPREV);
z++;
}
zOrder = int.MinValue;
return false;
}
}
}
// Find z-order for window.
Process[] procs = Process.GetProcessesByName("notepad");
Process top = null;
int topz = int.MaxValue;
foreach (Process p in procs)
{
IntPtr handle = p.MainWindowHandle;
int z = 0;
do
{
z++;
handle = GetWindow(handle, 3);
} while(handle != IntPtr.Zero);
if (z < topz)
{
top = p;
topz = z;
}
}
if(top != null)
Debug.WriteLine(top.MainWindowTitle);
For get Z-Order implement this function (by using GetWindow
Windows API function)
[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr GetWindow(IntPtr hWnd, uint uCmd);
static int GetWindowZOrder(IntPtr hWnd)
{
var zOrder = -1;
while ((hWnd = GetWindow(hWnd, 2 /* GW_HWNDNEXT */)) != IntPtr.Zero) zOrder++;
return zOrder;
}
The return value is a zero-based index. Returning -1 indicates an invalid hWnd.
The approach is to go up through the windows to the top. The total number of climbs is the value of the Z-Order.