How to get CEdit to scroll properly? - mfc

Question

I have a CEdit control that's used to display a diagnostics output.
Sometimes the data overflows the screen size, so naturally I set the Vertical Scroll property to true (MFC dialog editor).
But then, when I tried to scroll the text that was in the window before isn't cleared and the new text is written over it.
The result is a big mess of everything I have scrolled past.
I've looked for a draw background property or something similar that will erase everything in the window while scrolling (before redrawing the new data).
Any suggestions?

Answer 1

I think you might want to set Auto VScroll and Multiline to true, and Auto HScroll to false.

Answer 2

We were having a similar problem. We ended up having to invalid the region of the parent window to get it to update when we got WM_VSCROLL. I tried to do as user demorge says here:
SetBkMode(hdc, TRANSPARENT) doesn't work
But our code doesn't use handles, we actually use the class CWnd, so we ended up doing this in the WindowProc instead:
switch(message)
{
...
case WM_VSCROLL:
case WM_HSCROLL:
LRESULT answer;
PAINTSTRUCT ps;
CDC* pdc;
CWnd* MyParentHWnd;
// We want the scroll to work the same way it has always worked for our
// ancestor class. Let them handle the scrolling and save off their
// return.
answer = AncestorClass::WindowProc(message, wParam, lParam);
pdc = BeginPaint(&ps);
// DO NOT change the assignement operator in the conditional below to an
// equality operator. We are actually trying to get the parent window and
// and storing locally, and then verifying that we didn't get back null.
// This is a purposeful design decision.
if (MyParentHWnd = GetParent()){
RECT MyRect;
GetClientRect(&MyRect);
ClientToScreen(&MyRect);
MyParentHWnd->ScreenToClient(&MyRect);
MyParentHWnd->InvalidateRect(&MyRect);
}
EndPaint(&ps);
return answer;
break;
...
}
Of course, I had to genericize it a little bit. I just wanted you to know that yes, there are other people that are seeing your problem, and we found how to fix it.

Answer 3

I tested this with VS2005, which ships with MFC 8.0. I couldn't replicate your problem.
I added one CEdit and one CRichEditCtrl to a dialog based app. Changed properties Multiline, Auto VSCroll and Vertical Scroll to true. Used SetWindowText-method to put loooooong string of text to both of them. I started the app and text scrolled just fine.
What did you do differently?
Just to be sure. You didn't use the SetCaretPos-method, did you? There was some note about that in the MSDN page. Here's the Knowledge Base article.