protected IntPtr HandleNCHitTest(IntPtr lParam)
{
// Because we still have the System Border (which technically extends beyond the actual window
// into where the Drop shadows are), we can use DefWindowProc here to handle resizing, except
// on the top. We'll handle that below
var originalRet = Win32Interop.DefWindowProc(Hwnd, (uint)WM.NCHITTEST, IntPtr.Zero, lParam);
if (originalRet != new IntPtr(1))
{
return(originalRet);
}
// At this point, we know that the cursor is inside the client area so it
// has to be either the little border at the top of our custom title bar,
// the drag bar or something else in the XAML island. But the XAML Island
// handles WM_NCHITTEST on its own so actually it cannot be the XAML
// Island. Then it must be the drag bar or the little border at the top
// which the user can use to move or resize the window.
var point = PointToClient(PointFromLParam(lParam));
RECT rcWindow;
Win32Interop.GetWindowRect(Hwnd, out rcWindow);
// On the Top border, the resize handle overlaps with the Titlebar area, which matches
// a typical Win32 window or modern app window
var resizeBorderHeight = GetResizeHandleHeight();
bool isOnResizeBorder = point.Y < resizeBorderHeight;
// Make sure the caption buttons still get precedence
// This is where things get tricky too. On Win11, we still want to suppor the snap
// layout feature when hovering over the Maximize button. Unfortunately no API exists
// yet to call that manually if using a custom titlebar. But, if we return HT_MAXBUTTON
// here, the pointer events no longer enter the window
// See https://github.com/dotnet/wpf/issues/4825 for more on this...
// To hack our way into making this work, we'll return HT_MAXBUTTON here, but manually
// manage the state and handle stuff through the WM_NCLBUTTON... events
// This only applies on Windows 11, Windows 10 will work normally b/c no snap layout thing
if (_owner !.HitTestCaptionButtons(point))
{
if (_isWindows11)
{
var result = _owner.HitTestMaximizeButton(point);
if (result)
{
_fakingMaximizeButton = true;
return(new IntPtr(9));
}
}
}
private void ViewerPosUpdateHandler(object obj)
{
if (mainWindowHandle != IntPtr.Zero && dock != DockType.None)
{
if (Win32Interop.IsWindowVisible(mainWindowHandle))
{
if (!Win32Interop.IsZoomed(mainWindowHandle))
{
Win32Interop.Rect currentPosition;
Win32Interop.GetWindowRect(mainWindowHandle, out currentPosition);
if (!currentPosition.IsSame(lastPosition))
{
this.SafeInvoke(() =>
{
ViewerPosUpdate(currentPosition);
});
lastPosition = currentPosition;
}
}
}
}
}