-0.5 is causing trouble according to comments in bug #783

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403932

src/video/SDL_renderer_gl.c

@@ -448,8 +448,8 @@ GL_ActivateRenderer(SDL_Renderer * renderer)
         data->glMatrixMode(GL_MODELVIEW);
         data->glLoadIdentity();
         data->glViewport(0, 0, window->w, window->h);
-        data->glOrtho(-0.5, (GLdouble) window->w-0.5,
-                      (GLdouble) window->h-0.5, -0.5, 0.0, 1.0);
+        data->glOrtho(0.0, (GLdouble) window->w,
+                      (GLdouble) window->h, 0.0, 0.0, 1.0);
         data->updateSize = SDL_FALSE;
     }
     return 0;