BOOL GDIplusChord( HDC hDC, INT x1, INT y1, INT x2, INT y2, INT x3, INT y3, INT x4, INT y4 )
{
Graphics graphics(hDC);
CRect rectBound(x1, y1, x2, y2);
rectBound.NormalizeRect();
Rect ellipseRect(rectBound.left, rectBound.top, rectBound.Width(), rectBound.Height());
////////////////////////////////////////////////////////////////////////////////
// For testing only.
BYTE byAlpha = 200;
SolidBrush fillBrush(Color(byAlpha, 0, 0, 255));
Pen redPen(Color(byAlpha, 255, 0, 0), 3);
////////////////////////////////////////////////////////////////////////////////
Status ret = InvalidParameter;
if ( x3 == x4 && y3 == y4 )
{
// If the starting point and ending point of the curve are the same, a complete ellipse should be drawn.
ret = graphics.FillEllipse(&fillBrush, ellipseRect);
ret = graphics.DrawEllipse(&redPen, ellipseRect);
return Gdiplus::Ok == ret;
}
CPoint ptCenter(rectBound.CenterPoint());
#define PI 3.1415926
REAL startAngle = atan2(y3-ptCenter.y, x3-ptCenter.x ) * 180.0f / PI;
REAL sweepAngle = (atan2(y4-ptCenter.y, x4-ptCenter.x ) * 180.0f / PI) - startAngle - 360.0f;
if ( sweepAngle < -360.0f )
sweepAngle += 360.0f;
GraphicsPath path;
path.StartFigure();
path.AddArc(ellipseRect, startAngle, sweepAngle);
path.CloseFigure();
ret = graphics.FillPath(&fillBrush, &path);
ret = graphics.DrawPath(&redPen, &path);
return Gdiplus::Ok == ret;
}