CScrollView adds basic scrolling capabilities to CView.
2025-11-29
Written by: xiaobin
CScrollView adds basic scrolling capabilities to CView. It includes handlers for WM_VSCROLL and WM_HSCROLL messages that allow MFC to do the bulk of the work involved in scrolling a window in response to scroll bar messages. It also includes member functions that you can call to perform fundamental tasks such as scrolling to a specified position and retrieving the current scroll position. Because CScrollView handles scrolling entirely on its own, you have to do very little to make it work other than implement OnDraw. You can usually implement OnDraw in a CScrollView exactly as you do in a CView. Unless you want to tweak it to optimize scrolling performance, OnDraw requires little or no special logic to support scrolling.
Override OnInitialUpdate in the view class, and call SetScrollSizes to specify the view’s logical dimensions. This is your means of telling MFC how large an area the scrollable view should cover. If you use AppWizard to create the project and choose CScrollView in the Step 6 dialog box, AppWizard overrides OnInitialUpdate for you and inserts a call to SetScrollSizes that sets the view’s logical width and height to 100 pixels.
Implement OnDraw as if the view were a conventional CView.
The demo program is missing a variable type definition—int.
Adding int will solve the problem:
//
// Add numbers and button outlines to the row headers.
//
for (int i=0; i<19; i++) {
// some code
} //
// Add letters and button outlines to the column headers.
//
for (int j=0; j<26; j++) {
// some code here
} //
// Draw address labels into the individual cells.
//
CRect rect;
pDC->GetClipBox (&rect);
// other code here
int nEndRow = min (18, (rect.bottom - 1) / m_nCellHeight);
// other code here
for (int i=nStartRow; i<=nEndRow; i++)
for (int j=nStartCol; j<=nEndCol; j++)
DrawAddress (pDC, i, j);