WPF Window and WndProc - wpf

Question

The code snipper below is taken from "WPF 4 Unleashed". it demonstrates hwo in windows 7 it's possible to create the Aero Glass effect using WIN32 API. In this demo, the WndProc events procedure is used with respect to the Window instance. I noticed that in this routine there is no invocation of the default window procedure, as if there are no other events that need to be handled by that WPF window.
What brings me to post that question -- which is more of a general question regarding WPF -- is whether the events that are normally handles by WPF window (and I am sure there are many of them) are handled by some other procedure. In other words, is WPF window different than WinForms --- does it gets messages from Operating system (mouse clicking, mouse movements) by other means ?
[StructLayout(LayoutKind.Sequential)]
public struct MARGINS
{
public MARGINS(Thickness t)
{
Left = (int)t.Left;
Right = (int)t.Right;
Top = (int)t.Top;
Bottom = (int)t.Bottom;
}
public int Left;
public int Right;
public int Top;
public int Bottom;
}
public class GlassHelper
{
[DllImport("dwmapi.dll", PreserveSig=false)]
static extern void DwmExtendFrameIntoClientArea( IntPtr hWnd, ref MARGINS pMarInset);
[DllImport("dwmapi.dll", PreserveSig=false)]
static extern bool DwmIsCompositionEnabled();
public static bool ExtendGlassFrame(Window window, Thickness margin)
{
if (!DwmIsCompositionEnabled())
return false;
IntPtr hwnd = new WindowInteropHelper(window).Handle;
if (hwnd == IntPtr.Zero)
throw new InvalidOperationException(
"The Window must be shown before extending glass.");
// Set the background to transparent from both the WPF and Win32 perspectives
window.Background = Brushes.Transparent;
HwndSource.FromHwnd(hwnd).CompositionTarget.BackgroundColor =Colors.Transparent;
MARGINS margins = new MARGINS(margin);
DwmExtendFrameIntoClientArea(hwnd, ref margins);
return true;
}
}
protected override void OnSourceInitialized(EventArgs e)
{
base.OnSourceInitialized(e);
// This can’t be done any earlier than the SourceInitialized event:
GlassHelper.ExtendGlassFrame(this, new Thickness(-1));
// Attach a window procedure in order to detect later enabling of desktop
// composition
IntPtr hwnd = new WindowInteropHelper(this).Handle;
HwndSource.FromHwnd(hwnd).AddHook(new HwndSourceHook(WndProc));
}
private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
if (msg == WM_DWMCOMPOSITIONCHANGED)
{
// Reenable glass:
GlassHelper.ExtendGlassFrame(this, new Thickness(-1));
handled = true;
}
return IntPtr.Zero;
}
private const int WM_DWMCOMPOSITIONCHANGED = 0x031E;

Answer 1

WPF window is the same as WinForms window in terms of using WndProc. I had no problem to put the snippet into my WPF app. In fact, I didn't find any WndProc related code, that didn't work in WPF so far.

Answer 2

WPF windows are like Windows Forms windows and like classic Windows windows in that they all have a Message Loop for receiving messages and a WindowProc (the actual name can be whatever the programmer chooses to make it) to process them. All the windows can be subclassed (as in About Window Procedures), at least at the level below WPF. I don't know if WndProc for Windows Forms or for WPF are subclassing the relevant windows but they might be.