Rounding errors between GDI+ & GDI ...

Hello,

Please consider the following code :

void Test (HDC hDC)
{
// Set graphics mode to 72 dpi ...
SetMapMode(hDC, MM_ISOTROPIC);
SetWindowExtEx(hDC, 72, 72, NULL);
SetViewportExtEx(hDC, GetDeviceCaps(hDC, LOGPIXELSX), GetDeviceCaps(hDC, LOGPIXELSY), NULL);
SetGraphicsMode(hDC, GM_ADVANCED);

// Draw a 2x2 inch rectangle using GDI
HBRUSH hbOld = (HBRUSH)SelectObject(hDC, (HBRUSH)GetStockObject(NULL_BRUSH));
Rectangle(hDC, 100, 100, 100 + 144, 100 + 144);
SelectObject(hDC, hbOld);

// Draw over a 2x2 inch rectangle using GDI+
Graphics g(hDC);
SolidBrush br(Color(200, 255, 128, 0));
g.FillRectangle(&br, 100, 100, 144, 144);
}


It demonstrates that if you draw a GDI+ primitive over a GDI one, they do not perfectly overlap when the GDI mapping mode is not trivial. I guess that the Graphics objet performs some additionnal transformations to mimic the GDI mapping mode. Problem is: the result is not the same as drawing through the GDI internal matrix.

Any clue how to bypass this problem (without giving up the GDI transformations of course)?

Thanks,
Jean-Ed.
.

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