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AnswerRe: How to stop flickering of controls in my Dialog window Pin
Victor Nijegorodov28-Feb-19 1:02
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AnswerRe: How to stop flickering of controls in my Dialog window Pin
leon de boer1-Mar-19 6:48
memberleon de boer1-Mar-19 6:48 
I am not a real fan of MFC but I can tell you what windows API is doing.

Dialog backgrounds paint by WM_CTLCOLORDLG, WM_CTLCOLORSTATIC it used to be WM_CTLCOLOR and I suspect MFC still uses WM_CTLCOLOR because it has a couple of bugs.

Usually what you want to do is return a NULL_BRUSH with GetStockObject(NULL_BRUSH);

So this one if you paint the entire dialog then return a NULL_BRUSH
WM_CTLCOLORDLG message - Windows applications | Microsoft Docs[^]

MFC may use this one and again return a NULL_BRUSH
WM_CTLCOLOR message - Windows applications | Microsoft Docs[^]

That means it doesn't paint the background before it sends you an WM_PAINT Smile | :)

If you want/need to transparent overlay the bitmap you have to use a transparent colour to stop flashing
void CDemoDialog::OnPaint()
{
   CPaintDC dc(this); // device context for painting
 
   // transfer the bitmap into paint DC using a transparent color  
   dc.TransparentBlt(
      10, 10, bmp.bmWidth, bmp.bmHeight, // destination coordinates and sizes
      &pDCTmp,                           // source DC .. your DC with bitmap
      0, 0, bmp.bmWidth, bmp.bmHeight,   // source coordinates and sizes
      RGB(255, 0, 0));                   // transparent color

}

In vino veritas


modified 1-Mar-19 12:54pm.

QuestionDialog box margins Pin
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