Scrolling Help

[tirilo]

Hi,

I am a beginner. I am drawing a sound waveform in a CScrollview derived view.
When I use the scroll bars, the drawing moves accordingly but in a persistent manner: All the previous plots stay on screen until their region gets invalidated.

When the whole view is invalidated, the original waveform gets redrawned in the original position relative to the view (device coordinates). It seems not to have noticed the fact that the scrolling bars are not at the same place anymore.

I have tried to use calls to OnPrepareDC and DPtoLP at various places in my code but until now nothing seems to change.

Can anybody give me some hints ?

Thank you very much

[zackattach]

Did you ever fix this? I have the same problem. I'm trying to draw rectangles that seem to draw on themselves again upon scrolling in either direction. Also, the rectangles are completely redrawn when I minimize then restore the window but apparently the origin moves.

My code to draw the rectangles is

CRect TempRect = pDoc->GetNode(i); // The points for the rectangle
OnPrepareDC(pDC);
pDC->DPtoLP(&TempRect);
pDC->Rectangle(TempRect);

and I set the scroll bars sizes in OnInitialUpdate with

CSize Workspace(1000, 1000);
SetScrollSizes(MM_LOENGLISH, Workspace);

I have tried a variety of fixes in OnPrepareDC included setting the mapping mode to MM_LOENGLISH and setting the origin at 0, 0 but nothing works.

Any help?

[hoxsiew]

You should check out the DrawCLI sample in the MSDN samples.