Advanced MFC Programming

Chapter 6. Dialog Box
Sample
Sampel 6.5\DB demonstrates background customization. It is a standard dialog-based application
generated from Application Wizard. In the sample, instead of using a uniform color, the dialog box paints
its background with a bitmap image (Figure 6-3).
Figure 6-3. Customize the background of a dialog box
Because WM_ERASEBKGND is not listed as a dialog box message, first we need to customize the filter
settings for this application. We can do this by invoking Class Wizard, clicking “Class Info” tab then
changing the default setting in combo box “Message Filter” from “Dialog” to “Window”. By going back to
“Message maps” page now, we can find WM_ERASEBKGND in “Message” window, and add a message handler
for it. The function name should be CDBDlg::OnEraseBkgnd(…).
In the sample, a bitmap resource IDB_BITMAP_DLGBGD is added to the application, which will be used to
draw the background of the dialog box. In function CDBDlg::OnEraseBkgnd(…), this bitmap is painted
repeatedly until all dialog box area is covered by it:
BOOL CDBDlg::OnEraseBkgnd(CDC *pDC)
{
CBitmap bmp;
CBitmap *ptrBmpOld;
CDC dcMemory;
BITMAP bm;
CRect rect;
int i, j;
int nHor, nVer;
bmp.LoadBitmap(IDB_BITMAP_DLGBGD);
bmp.GetBitmap(&bm);
GetClientRect(rect);
nHor=rect.Width()/bm.bmWidth+1;
nVer=rect.Height()/bm.bmHeight+1;
dcMemory.CreateCompatibleDC(pDC);
ptrBmpOld=dcMemory.SelectObject(&bmp);
for(i=0; i