//-------------------------------------------------------------------
/// 現在の対象ウィンドウのClient領域をXORで塗りつぶす
private void XorTargetWindowRect()
{
User32.RECT currentTargetRect;
User32.GetClientRect(this.currentTargetWindow, out currentTargetRect);
var originalDrawMode = GDI32.SetROP2(this.currentTargetDC, GDI32.R2_XORPEN);
var originalPen = GDI32.SelectObject(this.currentTargetDC, App.NullPen.Pen);
GDI32.Rectangle(this.currentTargetDC,
currentTargetRect.Left, currentTargetRect.Top,
currentTargetRect.Right, currentTargetRect.Bottom);
GDI32.SelectObject(this.currentTargetDC, originalPen);
GDI32.SetROP2(this.currentTargetDC, originalDrawMode);
}