# Coding Life

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GDI+并没有提供GDI中的Chord函数（其它的还有RoundRect函数，可参考BobPowell 的这篇文章），只好自己动手了：

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();