Problem on refresh view area in MFC view image display application

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I'm developing an MFC Doc/View application to display an image with functions zoom in, zoom out etc. I'm using stretchBlt in CScrollview::OnDraw While zooming out the image, the remaining view area where not repainting not getting cleared, ie part of the image of previous draws remaining as such. While doing minimize & maximize after zoomout, they becoming cleared. Also I tried to paint the view area with its background color using FillSolidRect method, then its working, but problem is it adding an annoying flicker in image display.
I tried Invalidate & UpdateWindow in functions in my Zoomout()method but it is not working.

The actual problem is while I zooming out, the StretchBlt the painting area of StretchBlt getting lesser than previous rectangle and remaining part of the view remaining unchanged.

Have method to refresh & clear the view area were not repainted?

Posted 17-Mar-14 20:09pm

the vacuum

Updated 18-Mar-14 0:34am

v3

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Richard MacCutchan 18-Mar-14 5:12am

If you invalidate the entire client area then its background should be completely erased. You then repaint with the new zoomed part of the image. Have you checked that your destination coordinates cover the entire client area?

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CPallini · Answer 1 · 2014-03-18T01:18:00

Solution 1

Calling InvalidateRect[^] (and then UpdateWindow) passing the full rectangle should be enough. To remove the flickering you should avoid updating it continually.

Posted 18-Mar-14 1:18am

CPallini