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Home > Forums > Programmers > Development Tools > Embarcadero: C++Builder Forum

Windows Graphics problem, HRGN region repainting problem

thread101-1640626
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vvozar (Programmer)
5 Mar 11 12:12
Hello,

   The issue is related to Windows GDI, actually about repainting "framed" regions (HRGN framed with "FrameRgn" function)
   I'm making application using BCB including VCL library. I put TImage component/object on an empty form and loaded proper bitmap image to Picture property of that image.
   Then i wrote form's method that paints a frame around 'img':

CODE

void __fastcall drawFrame()
{
 rgb = 0x00ffeeff; // light gray RGB color code

 // creating region on image area, 26 is width of caption in pixels
 // frame will be 4 pixels width around image

 rgn = CreateRoundRectRgn(form->Left + img1->Left + 2,
  form->Top + 26 + img1->Top + 2,
  form->Left + img1->Left + img1->Width + 11,
  form->Top + 26 + img1->Top + img1->Height + 11,
  4 , 4);

 hdc = GetDC(hWnd);
 brush = CreateSolidBrush(rgb);
 FrameRgn(hdc, rgn, brush, 4, 4);
 ReleaseDC(hWnd,hdc);
 DeleteObject(rgn);
}
Wanting always to have frame around my image, i am calling this method in OnPaint event.

CODE

void __fastcall TfrmMainForm::FormPaint(TObject *Sender)
{
    drawFrame();
}
When OnPaint event occurs everything is repainted fine, except in one situation. When my forms window is not top most (i drag some other opened window above it - like windows explorer), those region frame around image is being redrawed on top of the foreground window. I understand that it is normal because of the nature of an OnPaint event, but don't know the way to avoid this situation.
I mean, how to disable that repainting regions frame on top of foreground window - window that's not my applications window?

Appreciate any help or advice.
vvozar (Programmer)
9 Mar 11 6:32
Instead of using regions, device contexts and brushes, i will draw directly on the form.
I've changed code in drawFrame() method to:

CODE

void __fastcall TfrmMainForm::drawFrame()
{
        form->Canvas->Pen->Style = psSolid;
        form->Canvas->Pen->Width = 4;
        form->Canvas->Pen->Color = clLtGray;
        form->Canvas->Brush->Style = bsClear;
        form->Canvas->Rectangle(
          img->Left - 2,
          img->Top  - 2,
          img->Left + img->Width + 2,
          img->Top  + img->Height + 2
          );
}
This way it draws directly on forms canvas, and requires less memory management (allocating and freeing) comparing to using regions and brushes.
To be able to draw directly on a form, FormStyle must be set either to fsNormal or fsStayOnTop.
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