/// <summary>
/// Begin using off-screen buffer and cache drawing which will be done after.
/// </summary>
/// <param name="paintRect">painting area (used for creating off-screen buffer).</param>
public void BeginPaint(Rectangle paintRect)
{
Debug.Assert(_MemDC == IntPtr.Zero, "invalid state; _MemDC must be IntPtr.Zero.");
Debug.Assert(_MemBmp == IntPtr.Zero, "invalid state; _MemBmp must be IntPtr.Zero.");
// create offscreen from the window DC
_MemDC = WinApi.CreateCompatibleDC(_DC);
_MemBmp = WinApi.CreateCompatibleBitmap(_DC, paintRect.Width, paintRect.Height);
_Offset = paintRect.Location;
_MemDcSize = paintRect.Size;
_OrgMemBmp = WinApi.SelectObject(_MemDC, _MemBmp);
}
/// <summary>
/// End using off-screen buffer and flush all drawing results.
/// </summary>
public void EndPaint()
{
Debug.Assert(_MemDC != IntPtr.Zero, "invalid state; EndPaint was called before"
+ " BeginPaint.");
const uint SRCCOPY = 0x00CC0020;
// flush cached graphic update
WinApi.BitBlt(_DC, _Offset.X, _Offset.Y, _MemDcSize.Width, _MemDcSize.Height,
_MemDC, 0, 0, SRCCOPY);
RemoveClipRect();
// dispose resources used in off-screen rendering
WinApi.SelectObject(_MemDC, _OrgMemBmp);
WinApi.DeleteDC(_MemDC);
_MemDC = IntPtr.Zero;
SafeDeleteObject(_MemBmp);
_MemBmp = IntPtr.Zero;
// reset graphic coordinate offset
_Offset.X = _Offset.Y = 0;
}