protected override LResult WindowProcedure(WindowHandle window, MessageType message, WParam wParam, LParam lParam)
{
switch (message)
{
case MessageType.Size:
cxClient = lParam.LowWord;
cyClient = lParam.HighWord;
CursorHandle hCursor = Windows.SetCursor(CursorId.Wait);
Windows.ShowCursor(true);
hRgnClip.Dispose();
Span <RegionHandle> hRgnTemp = stackalloc RegionHandle[6];
hRgnTemp[0] = Gdi.CreateEllipticRegion(Rectangle.FromLTRB(0, cyClient / 3, cxClient / 2, 2 * cyClient / 3));
hRgnTemp[1] = Gdi.CreateEllipticRegion(Rectangle.FromLTRB(cxClient / 2, cyClient / 3, cxClient, 2 * cyClient / 3));
hRgnTemp[2] = Gdi.CreateEllipticRegion(Rectangle.FromLTRB(cxClient / 3, 0, 2 * cxClient / 3, cyClient / 2));
hRgnTemp[3] = Gdi.CreateEllipticRegion(Rectangle.FromLTRB(cxClient / 3, cyClient / 2, 2 * cxClient / 3, cyClient));
hRgnTemp[4] = Gdi.CreateRectangleRegion(Rectangle.FromLTRB(0, 0, 1, 1));
hRgnTemp[5] = Gdi.CreateRectangleRegion(Rectangle.FromLTRB(0, 0, 1, 1));
hRgnClip = Gdi.CreateRectangleRegion(Rectangle.FromLTRB(0, 0, 1, 1));
hRgnTemp[4].CombineRegion(hRgnTemp[0], hRgnTemp[1], CombineRegionMode.Or);
hRgnTemp[5].CombineRegion(hRgnTemp[2], hRgnTemp[3], CombineRegionMode.Or);
hRgnClip.CombineRegion(hRgnTemp[4], hRgnTemp[5], CombineRegionMode.Xor);
for (int i = 0; i < 6; i++)
{
hRgnTemp[i].Dispose();
}
Windows.SetCursor(hCursor);
Windows.ShowCursor(false);
return(0);
case MessageType.Paint:
using (DeviceContext dc = window.BeginPaint())
{
dc.SetViewportOrigin(new Point(cxClient / 2, cyClient / 2));
dc.SelectClippingRegion(hRgnClip);
double fRadius = Hypotenuse(cxClient / 2.0, cyClient / 2.0);
for (double fAngle = 0.0; fAngle < TWO_PI; fAngle += TWO_PI / 360)
{
dc.MoveTo(default);
dc.LineTo(new Point(
(int)(fRadius * Math.Cos(fAngle) + 0.5),
(int)(-fRadius * Math.Sin(fAngle) + 0.5)));
}
}