Advanced MFC Programming

Chapter 11. Sample: Simple Paint
When we copy the image from the memory bitmap to the client window, we must calculate if the
whole bitmap contains valid image. If not, we should draw only the valid part:
……
……
pDC->BitBlt
(
i*size.cx*nRatio,
j*size.cy*nRatio,
(
(i+1)*size.cx*nRatio > bm.bmWidth*nRatio ?
(bm.bmWidth*nRatio-i*size.cx*nRatio):size.cx*nRatio
),
(
(j+1)*size.cy*nRatio > bm.bmHeight*nRatio ?
(bm.bmHeight*nRatio-j*size.cy*nRatio):size.cy*nRatio
),
&m_dcBKMem,
0,
0,
SRCCOPY
);
The grid drawing becomes very easy now. The brush origin can always be set to (0, 0) because both
the horizontal and vertical dimensions of the memory bitmap are even. Before the image contained in the
memory bitmap is copied to the client window, the grid is added if the current ratio is greater than 2 and the
value of CGDIDoc::m_bGridOn is TRUE:
……
……
m_brGrid.UnrealizeObject();
pDC->SetBrushOrg(0, 0);
pBrOld=m_dcBKMem.SelectObject(&m_brGrid);
for(i=0; i