Filling a Partially Rounded Rectangle with GDI+ - c++

Question

I have a rounded rectangle that I make like so
dc.RoundRect(textBorder, CPoint(20, 20));
Later on I draw a line through it about 1/3 of the way down.
dc.LineTo(textBorder.right, textBorder.top + 15);
Now I would like to fill just the part above the line with a solid color. In other words I need to fill a partially rounded rectangle, because the top of the rectangle is rounded, but the bottom of it is truncated by the line. Is there an easy way to do this?

Answer 1

Have you tried using a combination of CreateRoundRectRegion and then FillRgn to fill the non-rectangular area?
This the example given in the docs for CreateRoundRectRegion:
CRgn rgnA, rgnB, rgnC;
VERIFY(rgnA.CreateRoundRectRgn( 50, 50, 150, 150, 30, 30 ));
VERIFY(rgnB.CreateRoundRectRgn( 200, 75, 250, 125, 50, 50 ));
VERIFY(rgnC.CreateRectRgn( 0, 0, 50, 50 ));
int nCombineResult = rgnC.CombineRgn( &rgnA, &rgnB, RGN_OR );
ASSERT( nCombineResult != ERROR && nCombineResult != NULLREGION );
CBrush brA, brB, brC;
VERIFY(brA.CreateSolidBrush( RGB(255, 0, 0) ));
VERIFY(pDC->FillRgn( &rgnA, &brA)); // rgnA Red Filled
VERIFY(brB.CreateSolidBrush( RGB(0, 255, 0) ));
VERIFY(pDC->FillRgn( &rgnB, &brB)); // rgnB Green Filled
VERIFY(brC.CreateSolidBrush( RGB(0, 0, 255) )); // rgnC Blue
VERIFY(pDC->FrameRgn( &rgnC, &brC, 2, 2 ));
In general, when you want to do something with non-rectangular areas you have to start looking into regions.