private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
switch (msg)
{
// Ignore clicks if desktop composition isn't enabled
case DwmApiInterop.WM_NCHITTEST:
if (DwmApiInterop.IsCompositionEnabled() &&
DwmApiInterop.IsOnClientArea(hwnd, msg, wParam, lParam) &&
IsOnExtendedFrame(lParam.ToInt32()))
{
handled = true;
return(new IntPtr(DwmApiInterop.HTCAPTION));
}
return(IntPtr.Zero);
// Also toggle window frame painting on this window when desktop composition is toggled
case DwmApiInterop.WM_DWMCOMPOSITIONCHANGED:
try
{
AdjustWindowFrame();
}
catch (InvalidOperationException)
{
FallbackPaint();
}
return(IntPtr.Zero);
default:
return(IntPtr.Zero);
}
}
private void AdjustWindowFrame()
{
if (DwmApiInterop.IsCompositionEnabled())
{
ExtendFrameIntoClientArea(0, 0, 32, 35);
}
else
{
FallbackPaint();
}
}
private void ExtendFrameIntoClientArea(int left, int right, int top, int bottom)
{
var margins = new MARGINS {
cxLeftWidth = left, cxRightWidth = right, cyTopHeight = top, cyBottomHeight = bottom
};
int hresult = DwmApiInterop.ExtendFrameIntoClientArea(hwnd, ref margins);
if (hresult == 0)
{
hsource.CompositionTarget.BackgroundColor = Colors.Transparent;
Background = Brushes.Transparent;
}
else
{
throw new InvalidOperationException("Could not extend window frames in the main window.");
}
}
