Moves glGetError under config to prevent a performance drop on some platforms.

Tested By: Stan
Differential Revision: https://code.wildfiregames.com/D3620
This was SVN commit r24986.

binaries/data/config/default.cfg

@@ -91,6 +91,10 @@ fog = true
 silhouettes = true
 showsky = true
 
+; Uses a synchonized call to a GL driver to get an error state. Useful
+; for a debugging of a system without GL_KHR_debug.
+gl.checkerrorafterswap = false
+
 novbo = false
 
 ; Disable hardware cursors

source/renderer/Renderer.cpp

@@ -1459,10 +1459,14 @@ void CRenderer::EndFrame()
 
 void CRenderer::OnSwapBuffers()
 {
+	bool checkGLErrorAfterSwap = false;
+	CFG_GET_VAL("gl.checkerrorafterswap", checkGLErrorAfterSwap);
+	if (!checkGLErrorAfterSwap)
+		return;
 	PROFILE3("error check");
 	// We have to check GL errors after SwapBuffer to avoid possible
 	// synchronizations during rendering.
-	if (GLenum  err = glGetError())
+	if (GLenum err = glGetError())
 		ONCE(LOGERROR("GL error %s (0x%04x) occurred", ogl_GetErrorName(err), err));
 }