diff --git a/src/gui/sdlmain.cpp b/src/gui/sdlmain.cpp
index 96f00312..846e8e9f 100644
--- a/src/gui/sdlmain.cpp
+++ b/src/gui/sdlmain.cpp
@@ -55,6 +55,10 @@
 
 #if C_OPENGL
 #include "SDL_opengl.h"
+//Define to disable the usage of the pixel buffer object
+//#define DB_DISABLE_DBO
+//Define to report opengl errors
+//#define DB_OPENGL_ERROR
 
 #ifndef APIENTRY
 #define APIENTRY
@@ -224,8 +228,28 @@ struct SDL_Block {
 
 static SDL_Block sdl;
 
+#if C_OPENGL
+#ifdef DB_OPENGL_ERROR
+void OPENGL_ERROR(const char* message) {
+	GLenum r = glGetError();
+	if (r == GL_NO_ERROR) return;
+	LOG_MSG("errors from %s",message);
+	do {
+		LOG_MSG("%X",r);
+	} while ( (r=glGetError()) != GL_NO_ERROR);
+}
+#else 
+void OPENGL_ERROR(const char*) {
+	return;
+}
+#endif
+#endif
+
 #define SETMODE_SAVES 1  //Don't set Video Mode if nothing changes.
 #define SETMODE_SAVES_CLEAR 1 //Clear the screen, when the Video Mode is reused
+//Restart graphics subsystem of SDL when switching windowed and fullscreen in OPENGL
+//#define SETMODE_RESTARTS_SUBSYSTEM 1 
+
 SDL_Surface* SDL_SetVideoMode_Wrap(int width,int height,int bpp,Bit32u flags){
 #if SETMODE_SAVES
 	static int i_height = 0;
@@ -270,13 +294,50 @@ SDL_Surface* SDL_SetVideoMode_Wrap(int width,int height,int bpp,Bit32u flags){
 	}
 #endif //WIN32
 #endif //SETMODE_SAVES
+	
+
+#if C_OPENGL
+#ifdef SETMODE_RESTARTS_SUBSYSTEM
+	SDL_Surface* s = NULL;
+	Bit32u fx = flags ^i_flags;
+	Bit32u fa = flags & i_flags;
+	if (fa&SDL_OPENGL) {
+		if (fx & SDL_FULLSCREEN) {
+			if (!(flags & SDL_FULLSCREEN)) {
+				//RESTART FOR MACS
+				
+				//MAYBE move this above the Videomode call above and do not do the setvideomode below. 
+				//Yes this will mess up the title bar and icon. But it is for trying...
+
+				LOG_MSG("HIT RESTART");
+				SDL_QuitSubSystem(SDL_INIT_VIDEO);
+				SDL_InitSubSystem(SDL_INIT_VIDEO);
+				LOG_MSG("AFTERRESTART");
+				s = SDL_SetVideoMode(width,height,bpp,flags);
+				if (s == NULL) LOG_MSG("Failed to videomode");
+				glFinish();
+			}
+		}
+	}
+#else //SETMODE_RESTARTS_SUBSYSTEM
 	SDL_Surface* s = SDL_SetVideoMode(width,height,bpp,flags);
+#endif //SETMODE_RESTARTS_SUBSYSTEM
+#else  //C_OPENGL
+	SDL_Surface* s = SDL_SetVideoMode(width,height,bpp,flags);
+#endif
+
+
 #if SETMODE_SAVES
 	if (s == NULL) return s; //Only store when successful
 	i_height = height;
 	i_width = width;
 	i_bpp = bpp;
 	i_flags = flags;
+#endif
+#if C_OPENGL
+	if(flags & SDL_OPENGL) {
+		OPENGL_ERROR("after setmode in wrap");
+	}
 #endif
 	return s;
 }
@@ -715,7 +776,10 @@ dosurface:
 		}		
 
 		glMatrixMode (GL_PROJECTION);
-		glDeleteTextures(1,&sdl.opengl.texture);
+
+		if (sdl.opengl.texture > 0) {
+			glDeleteTextures(1,&sdl.opengl.texture);
+		}
  		glGenTextures(1,&sdl.opengl.texture);
 		glBindTexture(GL_TEXTURE_2D,sdl.opengl.texture);
 		// No borders
@@ -764,6 +828,9 @@ dosurface:
 		glEnd();
 
 		glEndList();
+
+		OPENGL_ERROR("End of setsize");
+
 		sdl.desktop.type=SCREEN_OPENGL;
 		retFlags = GFX_CAN_32 | GFX_SCALING;
 		if (sdl.opengl.pixel_buffer_object)
@@ -924,8 +991,11 @@ bool GFX_StartUpdate(Bit8u * & pixels,Bitu & pitch) {
 		if(sdl.opengl.pixel_buffer_object) {
 		    glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_EXT, sdl.opengl.buffer);
 		    pixels=(Bit8u *)glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_EXT, GL_WRITE_ONLY);
-		} else
+		} else {
 		    pixels=(Bit8u *)sdl.opengl.framebuf;
+		}
+		OPENGL_ERROR("end of start update");
+		if (pixels == NULL) return false;
 		pitch=sdl.opengl.pitch;
 		sdl.updating=true;
 		return true;
@@ -1237,7 +1307,7 @@ static void GUI_StartUp(Section * sec) {
 			}
 		}
 	}
-
+	Bit16u windowspercentage  = 0;
 	sdl.desktop.window.width  = 0;
 	sdl.desktop.window.height = 0;
 	const char* windowresolution=section->Get_string("windowresolution");
@@ -1251,13 +1321,20 @@ static void GUI_StartUp(Section * sec) {
 				*height = 0;
 				sdl.desktop.window.height = (Bit16u)atoi(height+1);
 				sdl.desktop.window.width  = (Bit16u)atoi(res);
+			} else {
+				char* percentage = const_cast<char*>(strchr(windowresolution,'%'));
+				if(percentage && *percentage) {
+					*percentage = 0;
+					windowspercentage = (Bit16u) atoi(res);
+					if (windowspercentage) putenv(const_cast<char*>("SDL_VIDEO_CENTERED=1"));
+				}
 			}
 		}
 	}
 	sdl.desktop.doublebuf=section->Get_bool("fulldouble");
 #if SDL_VERSION_ATLEAST(1, 2, 10)
-#ifdef WIN32
 	const SDL_VideoInfo* vidinfo = SDL_GetVideoInfo();
+#ifdef WIN32
 	if (vidinfo) {
 		int sdl_w = vidinfo->current_w;
 		int sdl_h = vidinfo->current_h;
@@ -1271,15 +1348,32 @@ static void GUI_StartUp(Section * sec) {
 	if (!sdl.desktop.full.width || !sdl.desktop.full.height){
 		//Can only be done on the very first call! Not restartable.
 		//On windows don't use it as SDL returns the values without taking in account the dpi scaling
-		const SDL_VideoInfo* vidinfo = SDL_GetVideoInfo();
 		if (vidinfo) {
 			sdl.desktop.full.width = vidinfo->current_w;
 			sdl.desktop.full.height = vidinfo->current_h;
 		}
 	}
+	
+	if (!sdl.desktop.window.width || !sdl.desktop.window.height) {
+		if (vidinfo && windowspercentage) {
+			sdl.desktop.window.width = ((vidinfo->current_w*windowspercentage)/3200)*32;
+			sdl.desktop.window.height = ((vidinfo->current_h*windowspercentage)/2400)*24;
+		}
+	}
+
+
 #endif
 #endif
 
+#ifdef WIN32
+	//Can use the same code as above, if the OS scaling is disabled.
+	if (!sdl.desktop.window.width && windowspercentage) {
+		sdl.desktop.window.width = ((GetSystemMetrics(SM_CXSCREEN)*windowspercentage)/3200)*32;
+	}
+	if (!sdl.desktop.window.height && windowspercentage) {
+		sdl.desktop.window.height = ((GetSystemMetrics(SM_CYSCREEN)*windowspercentage)/2400)*24;
+	}
+#endif
 	if (!sdl.desktop.full.width) {
 #ifdef WIN32
 		sdl.desktop.full.width=(Bit16u)GetSystemMetrics(SM_CXSCREEN);
@@ -1359,7 +1453,10 @@ static void GUI_StartUp(Section * sec) {
 				sdl.opengl.paletted_texture = false;
 				sdl.opengl.pixel_buffer_object = false;
 			}
-			LOG_MSG("OpenGL extensions: packed pixel %d, paletted_texture %d, pixel_bufer_object %d",sdl.opengl.packed_pixel,sdl.opengl.paletted_texture,sdl.opengl.pixel_buffer_object);
+#ifdef DB_DISABLE_DBO
+			sdl.opengl.pixel_buffer_object = false;
+#endif
+			LOG_MSG("OpenGL extension: pixel_bufer_object %d",sdl.opengl.pixel_buffer_object);
 		}
 	} /* OPENGL is requested end */