Accessing and handling WndProc in USD
Everything in Windows is a window, from buttons to dialogs to everything in between. Same principle still applies to WPF applications such as USD. I recently had a requirement that I needed to release some external resources in USD before the AgentDesktop was destroyed. To do that, all I had to do was to add a hook to a HwndSource and write a pseudo window procedure. The message I was interested in handling was WM_DESTROY (0x0002)
HwndSrc = PresentationSource.FromVisual(Application.Current.MainWindow) as HwndSource;
HwndSrc?.AddHook(PseudoWndProc);
/// <summary>
/// Pseudoes the WND proc.
/// </summary>
/// <param name="hWnd">The h WND.</param>
/// <param name="msg">The MSG.</param>
/// <param name="wParam">The w parameter.</param>
/// <param name="lParam">The l parameter.</param>
/// <param name="handled">if set to <c>true</c> [handled].</param>
/// <returns></returns>
private IntPtr PseudoWndProc(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled) {
var retval = IntPtr.Zero;
switch (msg) {
case Win32Helper.WM_DESTROY:
// Release external resources here
break;
}
return retval;
}