Using SDL+OpenGL - White pixels in the corners of the window?
lazarus / 33-macOS - Mac OS X

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ZXDunny · 2016-03-31 10:22

Hi all - Little help?

I've been messing around porting a windows app to OSX - I've got it
building in Linux for ARM and x86 without issues, replacing the only
visual component with an SDL surface (the entire thing runs in one
surface only for output).

Using SDL for OSX firstly gets the colours backwards (ugh) and also is
limited to 30fps. Having looked around, I have implemented OpenGL for
the display by using a texture as the surface instead of the SDL
surface - but I'm still using SDL to open the main window. Now the
colours are correct, and the speed is lovely.

But! I'm getting white pixels in the bottom corners (Sorry for the
huge image!):

http://s27.postimg.org/7y5nwut35/Screen_Shot_2016_03_30_at_16_18_17.pn
g

Here's the code to open the window:

Code: [Select]  If FullScreen Then Begin

    Screen := SDL_SetVideoMode(Width, Height, 32, SDL_FULLSCREEN or
SDL_HWSURFACE{$IFDEF OPENGL} or SDL_OPENGL{$ENDIF});
    SPFULLSCREEN := True;
    Result := Screen <> nil;

  end Else Begin

    Screen := SDL_SetVideoMode(Width, Height, 32, SDL_HWSURFACE
{$IFDEF OPENGL}or SDL_OPENGL{$ENDIF});
    SPFULLSCREEN := False;
    Result := Screen <> nil;

  end;

  FinalisePalette;

  {$IFDEF OPENGL}
  DISPLAYSTRIDE := Width * 4;
  SetLength(PixArray, Width * Height * 4);
  DISPLAYPOINTER := @PixArray[0];

  SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
  glClearColor(0, 0, 0, 0);
  glClearDepth(1);

  glViewPort(0, 0, Width, Height);

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity;

  glOrtho(0, Width, Height, 0, 1, -1);

  glMatrixMode(GL_MODELVIEW);
  glEnable(GL_TEXTURE_2D);
  glLoadIdentity;

  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, Width, Height, 0, GL_RGBA,
GL_UNSIGNED_BYTE, DISPLAYPOINTER);
  glTexParameterI(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameterI(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  glEnable(GL_TEXTURE_2D);
  {$ELSE}
  DISPLAYSTRIDE := Screen^.Pitch;
  DISPLAYPOINTER := Screen^.Pixels;
  {$ENDIF}

PixArray[] is just an array the size of the screen in longwords to
hold the surface data which is then used to build an OpenGL texture.

If I don't use OpenGL and just use a regular SDL window, I don't get
the white corners. With OpenGL I do.

Anyone know how to prevent or fix it?

Many thanks,

Paul.