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Combination of an OpenGL CView, and OpenGL CWnd, and GDI

Posted on 2003-11-07
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This is my first actual question to the site but I have lurked long enough and am ready to join.  I've got an open source game that's a port of the board game Settlers of Catan, and it uses OpenGL in a CView for the game rendering and GDI over that for information display and user interaction.  The game is available at http://www.settlers3d.net and the source is all at SourceForge.net under the project 'settlers3d'.

I am now in the process of adding a brand-new expansion to the game and I want to have a separate 3D rendering of the progress of a certain ship piece over a certain tile (called the 'barbarian attack' in the game).  This rendering will be informational only and totally static, meaning the users can't interact with it like they do the main CView OpenGL window.

I'm trying to create a new CWnd based OpenGL window for this barbarian attack that is displayed in its own area that overlays the OpenGL CView.  (It actually slides in and out from the side of the game window, but that's extemperaneous to the problem.)  I have created the new OpenGL CWnd and gotten it to display what I want, however, all of the Windows GDI drawing is now very messed up.  Here is a screenshot: http://www.settlers3d.net/images/gdiproblem.jpg
 
It seems that with the OpenGL CWnd turned on, all of the rendering contexts for the GDI drawing are incorrect.  If I comment out the Create() call for the CWnd, everything works properly again.  If I move the application window around, the GDI snaps back into correct drawing, but as soon as I do something in the game that changes the GDI information displays, nothing updates properly.

Does anyone have any idea what would cause this?  I don't want to clutter up the question with massive source code pastes, but I can post some links to the files on SourceForge if it would help.
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Question by:jmfugate
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jmfugate earned 0 total points
ID: 9703352
I figured out my own answer.  In the OnPaint handler for the CWnd derived class, you need the following calls:

/////////////////////////////////////////////////////////////////////////////
// drawing
/////////////////////////////////////////////////////////////////////////////
void CGLBaseWnd::OnPaint()
{
      PAINTSTRUCT ps;

      //prepare painting region
      BeginPaint(&ps);

      ... your code ...

      EndPaint(&ps);
}

The BeginPaint and EndPaint set the clipping regions properly for the window being drawn.  It wasn't actually related to the OpenGL code at all.

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