path: root/distrib/sdl-1.2.15/src/video/wincommon/SDL_wingl.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2012 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

/* WGL implementation of SDL OpenGL support */

#if SDL_VIDEO_OPENGL
#include "SDL_opengl.h"
#endif
#include "SDL_lowvideo.h"
#include "SDL_wingl_c.h"

#if SDL_VIDEO_OPENGL
#define DEFAULT_GL_DRIVER_PATH "OPENGL32.DLL"
#endif

/* If setting the HDC fails, we may need to recreate the window (MSDN) */
static int WIN_GL_ResetWindow(_THIS)
{
	int status = 0;

#ifndef _WIN32_WCE /* FIXME WinCE needs the UNICODE version of CreateWindow() */
	/* This doesn't work with DirectX code (see CVS comments) */
	/* If we were passed a window, then we can't create a new one */
	if ( !SDL_windowid && SDL_strcmp(this->name, "windib") == 0 ) {
		/* Save the existing window attributes */
		LONG style;
		RECT rect = { 0, 0, 0, 0 };
		style = GetWindowLong(SDL_Window, GWL_STYLE);
		GetWindowRect(SDL_Window, &rect);
		DestroyWindow(SDL_Window);
		WIN_FlushMessageQueue();

		SDL_resizing = 1;
		SDL_Window = CreateWindow(SDL_Appname, SDL_Appname,
		                          style,
		                          rect.left, rect.top,
		                          (rect.right-rect.left)+1,
		                          (rect.bottom-rect.top)+1,
		                          NULL, NULL, SDL_Instance, NULL);
		WIN_FlushMessageQueue();
		SDL_resizing = 0;

		if ( SDL_Window ) {
			this->SetCaption(this, this->wm_title, this->wm_icon);
		} else {
			SDL_SetError("Couldn't create window");
			status = -1;
		}
	} else
#endif /* !_WIN32_WCE */
	{
		SDL_SetError("Unable to reset window for OpenGL context");
		status = -1;
	}
	return(status);
}

#if SDL_VIDEO_OPENGL

static int ExtensionSupported(const char *extension, const char *extensions)
{
	const char *start;
	const char *where, *terminator;

	/* Extension names should not have spaces. */
	where = SDL_strchr(extension, ' ');
	if ( where || *extension == '\0' )
	      return 0;
	
	if ( ! extensions )
		return 0;

	/* It takes a bit of care to be fool-proof about parsing the
	 *      OpenGL extensions string. Don't be fooled by sub-strings,
	 *           etc. */
	
	start = extensions;
	
	for (;;)
	{
		where = SDL_strstr(start, extension);
		if (!where) break;
		
		terminator = where + SDL_strlen(extension);
		if (where == start || *(where - 1) == ' ')
	        if (*terminator == ' ' || *terminator == '\0') return 1;

		start = terminator;
	}
	
	return 0;
}

static int ChoosePixelFormatARB(_THIS, const int *iAttribs, const FLOAT *fAttribs)
{
	HWND hwnd;
	HDC hdc;
	HGLRC hglrc;
	const char * (WINAPI *wglGetExtensionsStringARB)(HDC) = 0;
	const char *extensions;
	int pformat = 0;
	UINT matches = 0;

	hwnd = CreateWindow(SDL_Appname, SDL_Appname, WS_POPUP | WS_DISABLED,
	                    0, 0, 10, 10,
	                    NULL, NULL, SDL_Instance, NULL);
	WIN_FlushMessageQueue();

	hdc = GetDC(hwnd);

	SetPixelFormat(hdc, ChoosePixelFormat(hdc, &GL_pfd), &GL_pfd);

	hglrc = this->gl_data->wglCreateContext(hdc);
	if ( hglrc ) {
		this->gl_data->wglMakeCurrent(hdc, hglrc);
	}

	wglGetExtensionsStringARB = (const char * (WINAPI *)(HDC))
		this->gl_data->wglGetProcAddress("wglGetExtensionsStringARB");

	if( wglGetExtensionsStringARB ) {
		extensions = wglGetExtensionsStringARB(hdc);
	} else {
		extensions = NULL;
	}

	this->gl_data->WGL_ARB_pixel_format = 0;
	if( ExtensionSupported("WGL_ARB_pixel_format", extensions) ) {
		BOOL (WINAPI *wglChoosePixelFormatARB)(HDC hdc, const int *piAttribIList, const FLOAT *pfAttribFList, UINT nMaxFormats, int *piFormats, UINT *nNumFormats);
		wglChoosePixelFormatARB =
			(BOOL (WINAPI *)(HDC, const int *, const FLOAT *, UINT, int *, UINT *))
			this->gl_data->wglGetProcAddress("wglChoosePixelFormatARB");
		if( wglChoosePixelFormatARB &&
		    wglChoosePixelFormatARB(hdc, iAttribs, fAttribs, 1, &pformat, &matches) && pformat ) {
			this->gl_data->WGL_ARB_pixel_format = 1;
		}
	}
	
	if ( hglrc ) {
		this->gl_data->wglMakeCurrent(NULL, NULL);
		this->gl_data->wglDeleteContext(hglrc);
	}
	ReleaseDC(hwnd, hdc);
	DestroyWindow(hwnd);
	WIN_FlushMessageQueue();

	return pformat;
}

#endif /* SDL_VIDEO_OPENGL */

int WIN_GL_SetupWindow(_THIS)
{
	int retval;
#if SDL_VIDEO_OPENGL
	int i;
	int iAttribs[64];
	int *iAttr;
	int *iAccelAttr = NULL;
	float fAttribs[1] = { 0 };
	const GLubyte *(WINAPI *glGetStringFunc)(GLenum);
	const char *wglext;

	/* load the gl driver from a default path */
	if ( ! this->gl_config.driver_loaded ) {
		/* no driver has been loaded, use default (ourselves) */
		if ( WIN_GL_LoadLibrary(this, NULL) < 0 ) {
			return(-1);
		}
	}

	/* Set up the pixel format descriptor with our needed format */
	SDL_memset(&GL_pfd, 0, sizeof(GL_pfd));
	GL_pfd.nSize = sizeof(GL_pfd);
	GL_pfd.nVersion = 1;
	GL_pfd.dwFlags = (PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL);
	if ( this->gl_config.double_buffer ) {
		GL_pfd.dwFlags |= PFD_DOUBLEBUFFER;
	}
	if ( this->gl_config.stereo ) {
		GL_pfd.dwFlags |= PFD_STEREO;
	}
	GL_pfd.iPixelType = PFD_TYPE_RGBA;
	GL_pfd.cColorBits = this->gl_config.buffer_size;
	GL_pfd.cRedBits = this->gl_config.red_size;
	GL_pfd.cGreenBits = this->gl_config.green_size;
	GL_pfd.cBlueBits = this->gl_config.blue_size;
	GL_pfd.cAlphaBits = this->gl_config.alpha_size;
	GL_pfd.cAccumRedBits = this->gl_config.accum_red_size;
	GL_pfd.cAccumGreenBits = this->gl_config.accum_green_size;
	GL_pfd.cAccumBlueBits = this->gl_config.accum_blue_size;
	GL_pfd.cAccumAlphaBits = this->gl_config.accum_alpha_size;
	GL_pfd.cAccumBits =
		(GL_pfd.cAccumRedBits + GL_pfd.cAccumGreenBits +
		 GL_pfd.cAccumBlueBits + GL_pfd.cAccumAlphaBits);
	GL_pfd.cDepthBits = this->gl_config.depth_size;
	GL_pfd.cStencilBits = this->gl_config.stencil_size;

	/* setup WGL_ARB_pixel_format attribs */
	iAttr = &iAttribs[0];

	*iAttr++ = WGL_DRAW_TO_WINDOW_ARB;
	*iAttr++ = GL_TRUE;
	*iAttr++ = WGL_RED_BITS_ARB;
	*iAttr++ = this->gl_config.red_size;
	*iAttr++ = WGL_GREEN_BITS_ARB;
	*iAttr++ = this->gl_config.green_size;
	*iAttr++ = WGL_BLUE_BITS_ARB;
	*iAttr++ = this->gl_config.blue_size;

	/* We always choose either FULL or NO accel on Windows, because of flaky
	   drivers. If the app didn't specify, we use FULL, because that's
	   probably what they wanted (and if you didn't care and got FULL, that's
	   a perfectly valid result in any case. */
	*iAttr++ = WGL_ACCELERATION_ARB;
	iAccelAttr = iAttr;
	if (this->gl_config.accelerated) {
		*iAttr++ = WGL_FULL_ACCELERATION_ARB;
	} else {
		*iAttr++ = WGL_NO_ACCELERATION_ARB;
	}

	if ( this->gl_config.alpha_size ) {
		*iAttr++ = WGL_ALPHA_BITS_ARB;
		*iAttr++ = this->gl_config.alpha_size;
	}

	*iAttr++ = WGL_DOUBLE_BUFFER_ARB;
	*iAttr++ = this->gl_config.double_buffer;

	*iAttr++ = WGL_DEPTH_BITS_ARB;
	*iAttr++ = this->gl_config.depth_size;

	if ( this->gl_config.stencil_size ) {
		*iAttr++ = WGL_STENCIL_BITS_ARB;
		*iAttr++ = this->gl_config.stencil_size;
	}

	if ( this->gl_config.accum_red_size ) {
		*iAttr++ = WGL_ACCUM_RED_BITS_ARB;
		*iAttr++ = this->gl_config.accum_red_size;
	}

	if ( this->gl_config.accum_green_size ) {
		*iAttr++ = WGL_ACCUM_GREEN_BITS_ARB;
		*iAttr++ = this->gl_config.accum_green_size;
	}

	if ( this->gl_config.accum_blue_size ) {
		*iAttr++ = WGL_ACCUM_BLUE_BITS_ARB;
		*iAttr++ = this->gl_config.accum_blue_size;
	}

	if ( this->gl_config.accum_alpha_size ) {
		*iAttr++ = WGL_ACCUM_ALPHA_BITS_ARB;
		*iAttr++ = this->gl_config.accum_alpha_size;
	}

	if ( this->gl_config.stereo ) {
		*iAttr++ = WGL_STEREO_ARB;
		*iAttr++ = GL_TRUE;
	}

	if ( this->gl_config.multisamplebuffers ) {
		*iAttr++ = WGL_SAMPLE_BUFFERS_ARB;
		*iAttr++ = this->gl_config.multisamplebuffers;
	}

	if ( this->gl_config.multisamplesamples ) {
		*iAttr++ = WGL_SAMPLES_ARB;
		*iAttr++ = this->gl_config.multisamplesamples;
	}

	*iAttr = 0;

	for ( i=0; ; ++i ) {
		/* Get the window device context for our OpenGL drawing */
		GL_hdc = GetDC(SDL_Window);
		if ( GL_hdc == NULL ) {
			SDL_SetError("Unable to get DC for SDL_Window");
			return(-1);
		}

		/* Choose and set the closest available pixel format */
		pixel_format = ChoosePixelFormatARB(this, iAttribs, fAttribs);
		/* App said "don't care about accel" and FULL accel failed. Try NO. */
		if ( ( !pixel_format ) && ( this->gl_config.accelerated < 0 ) ) {
			*iAccelAttr = WGL_NO_ACCELERATION_ARB;
			pixel_format = ChoosePixelFormatARB(this, iAttribs, fAttribs);
			*iAccelAttr = WGL_FULL_ACCELERATION_ARB;  /* if we try again. */
		}
		if ( !pixel_format ) {
			pixel_format = ChoosePixelFormat(GL_hdc, &GL_pfd);
		}
		if ( !pixel_format ) {
			SDL_SetError("No matching GL pixel format available");
			return(-1);
		}
		if ( !SetPixelFormat(GL_hdc, pixel_format, &GL_pfd) ) {
			if ( i == 0 ) {
				/* First time through, try resetting the window */
				if ( WIN_GL_ResetWindow(this) < 0 ) {
					return(-1);
				}
				continue;
			}
			SDL_SetError("Unable to set HDC pixel format");
			return(-1);
		}
		/* We either succeeded or failed by this point */
		break;
	}
	DescribePixelFormat(GL_hdc, pixel_format, sizeof(GL_pfd), &GL_pfd);

	GL_hrc = this->gl_data->wglCreateContext(GL_hdc);
	if ( GL_hrc == NULL ) {
		SDL_SetError("Unable to create GL context");
		return(-1);
	}
	if ( WIN_GL_MakeCurrent(this) < 0 ) {
		return(-1);
	}
	gl_active = 1;

	/* Get the wglGetPixelFormatAttribivARB pointer for the context */
	if ( this->gl_data->WGL_ARB_pixel_format ) {
		this->gl_data->wglGetPixelFormatAttribivARB =
			(BOOL (WINAPI *)(HDC, int, int, UINT, const int *, int *))
			this->gl_data->wglGetProcAddress("wglGetPixelFormatAttribivARB");
	} else {
		this->gl_data->wglGetPixelFormatAttribivARB = NULL;
	}

	/* Vsync control under Windows.  Checking glGetString here is
	 * somewhat a documented and reliable hack - it was originally
	 * as a feature added by mistake, but since so many people rely
	 * on it, it will not be removed.  strstr should be safe here.*/
	glGetStringFunc = WIN_GL_GetProcAddress(this, "glGetString");
	if ( glGetStringFunc ) {
		wglext = (const char *)glGetStringFunc(GL_EXTENSIONS);
	} else {
		/* Uh oh, something is seriously wrong here... */
		wglext = NULL;
	}
	if ( wglext && SDL_strstr(wglext, "WGL_EXT_swap_control") ) {
		this->gl_data->wglSwapIntervalEXT = WIN_GL_GetProcAddress(this, "wglSwapIntervalEXT");
		this->gl_data->wglGetSwapIntervalEXT = WIN_GL_GetProcAddress(this, "wglGetSwapIntervalEXT");
	} else {
		this->gl_data->wglSwapIntervalEXT = NULL;
		this->gl_data->wglGetSwapIntervalEXT = NULL;
	}
	if ( this->gl_config.swap_control >= 0 ) {
		if ( this->gl_data->wglSwapIntervalEXT ) {
			this->gl_data->wglSwapIntervalEXT(this->gl_config.swap_control);
		}
	}
#else
	SDL_SetError("WIN driver not configured with OpenGL");
#endif
	if ( gl_active ) {
		retval = 0;
	} else {
		retval = -1;
	}
	return(retval);
}

void WIN_GL_ShutDown(_THIS)
{
#if SDL_VIDEO_OPENGL
	/* Clean up OpenGL */
	if ( GL_hrc ) {
		this->gl_data->wglMakeCurrent(NULL, NULL);
		this->gl_data->wglDeleteContext(GL_hrc);
		GL_hrc = NULL;
	}
	if ( GL_hdc ) {
		ReleaseDC(SDL_Window, GL_hdc);
		GL_hdc = NULL;
	}
	gl_active = 0;

	WIN_GL_UnloadLibrary(this);
#endif /* SDL_VIDEO_OPENGL */
}

#if SDL_VIDEO_OPENGL

/* Make the current context active */
int WIN_GL_MakeCurrent(_THIS)
{
	int retval;

	retval = 0;
	if ( ! this->gl_data->wglMakeCurrent(GL_hdc, GL_hrc) ) {
		SDL_SetError("Unable to make GL context current");
		retval = -1;
	}
	return(retval);
}

/* Get attribute data from wgl. */
int WIN_GL_GetAttribute(_THIS, SDL_GLattr attrib, int* value)
{
	int retval;

	if (attrib == SDL_GL_SWAP_CONTROL) {
		if ( this->gl_data->wglGetSwapIntervalEXT ) {
			*value = this->gl_data->wglGetSwapIntervalEXT();
			return 0;
		}
		return -1;
	}

	if ( this->gl_data->wglGetPixelFormatAttribivARB ) {
		int wgl_attrib;

		switch(attrib) {
		    case SDL_GL_RED_SIZE:
			wgl_attrib = WGL_RED_BITS_ARB;
			break;
		    case SDL_GL_GREEN_SIZE:
			wgl_attrib = WGL_GREEN_BITS_ARB;
			break;
		    case SDL_GL_BLUE_SIZE:
			wgl_attrib = WGL_BLUE_BITS_ARB;
			break;
		    case SDL_GL_ALPHA_SIZE:
			wgl_attrib = WGL_ALPHA_BITS_ARB;
			break;
		    case SDL_GL_DOUBLEBUFFER:
			wgl_attrib = WGL_DOUBLE_BUFFER_ARB;
			break;
		    case SDL_GL_BUFFER_SIZE:
			wgl_attrib = WGL_COLOR_BITS_ARB;
			break;
		    case SDL_GL_DEPTH_SIZE:
			wgl_attrib = WGL_DEPTH_BITS_ARB;
			break;
		    case SDL_GL_STENCIL_SIZE:
			wgl_attrib = WGL_STENCIL_BITS_ARB;
			break;
		    case SDL_GL_ACCUM_RED_SIZE:
			wgl_attrib = WGL_ACCUM_RED_BITS_ARB;
			break;
		    case SDL_GL_ACCUM_GREEN_SIZE:
			wgl_attrib = WGL_ACCUM_GREEN_BITS_ARB;
			break;
		    case SDL_GL_ACCUM_BLUE_SIZE:
			wgl_attrib = WGL_ACCUM_BLUE_BITS_ARB;
			break;
		    case SDL_GL_ACCUM_ALPHA_SIZE:
			wgl_attrib = WGL_ACCUM_ALPHA_BITS_ARB;
			break;
		    case SDL_GL_STEREO:
			wgl_attrib = WGL_STEREO_ARB;
			break;
		    case SDL_GL_MULTISAMPLEBUFFERS:
			wgl_attrib = WGL_SAMPLE_BUFFERS_ARB;
			break;
		    case SDL_GL_MULTISAMPLESAMPLES:
			wgl_attrib = WGL_SAMPLES_ARB;
			break;
		    case SDL_GL_ACCELERATED_VISUAL:
			wgl_attrib = WGL_ACCELERATION_ARB;
			this->gl_data->wglGetPixelFormatAttribivARB(GL_hdc, pixel_format, 0, 1, &wgl_attrib, value);
			if ( *value == WGL_NO_ACCELERATION_ARB ) {
				*value = SDL_FALSE;
			} else {
				*value = SDL_TRUE;
			}
			return 0;
		    default:
			return(-1);
		}
		this->gl_data->wglGetPixelFormatAttribivARB(GL_hdc, pixel_format, 0, 1, &wgl_attrib, value);

		return 0;
	}

	retval = 0;
	switch ( attrib ) {
	    case SDL_GL_RED_SIZE:
		*value = GL_pfd.cRedBits;
		break;
	    case SDL_GL_GREEN_SIZE:
		*value = GL_pfd.cGreenBits;
		break;
	    case SDL_GL_BLUE_SIZE:
		*value = GL_pfd.cBlueBits;
		break;
	    case SDL_GL_ALPHA_SIZE:
		*value = GL_pfd.cAlphaBits;
		break;
	    case SDL_GL_DOUBLEBUFFER:
		if ( GL_pfd.dwFlags & PFD_DOUBLEBUFFER ) {
			*value = 1;
		} else {
			*value = 0;
		}
		break;
	    case SDL_GL_BUFFER_SIZE:
		*value = GL_pfd.cColorBits;
		break;
	    case SDL_GL_DEPTH_SIZE:
		*value = GL_pfd.cDepthBits;
		break;
	    case SDL_GL_STENCIL_SIZE:
		*value = GL_pfd.cStencilBits;
		break;
	    case SDL_GL_ACCUM_RED_SIZE:
		*value = GL_pfd.cAccumRedBits;
		break;
	    case SDL_GL_ACCUM_GREEN_SIZE:
		*value = GL_pfd.cAccumGreenBits;
		break;
	    case SDL_GL_ACCUM_BLUE_SIZE:
		*value = GL_pfd.cAccumBlueBits;
		break;
	    case SDL_GL_ACCUM_ALPHA_SIZE:
		*value = GL_pfd.cAccumAlphaBits;
		break;
	    case SDL_GL_STEREO:
		if ( GL_pfd.dwFlags & PFD_STEREO ) {
			*value = 1;
		} else {
			*value = 0;
		}
		break;
	    case SDL_GL_MULTISAMPLEBUFFERS:
		*value = 0;
		break;
	    case SDL_GL_MULTISAMPLESAMPLES:
		*value = 1;
		break;
	    case SDL_GL_SWAP_CONTROL:
		if ( this->gl_data->wglGetSwapIntervalEXT ) {
			*value = this->gl_data->wglGetSwapIntervalEXT();
			return 0;
		} else {
			return -1;
		}
		break;
	    default:
		retval = -1;
		break;
	}
	return retval;
}

void WIN_GL_SwapBuffers(_THIS)
{
	SwapBuffers(GL_hdc);
}

void WIN_GL_UnloadLibrary(_THIS)
{
	if ( this->gl_config.driver_loaded ) {
		FreeLibrary((HMODULE)this->gl_config.dll_handle);

		this->gl_data->wglGetProcAddress = NULL;
		this->gl_data->wglCreateContext = NULL;
		this->gl_data->wglDeleteContext = NULL;
		this->gl_data->wglMakeCurrent = NULL;
		this->gl_data->wglGetPixelFormatAttribivARB = NULL;
		this->gl_data->wglSwapIntervalEXT = NULL;
		this->gl_data->wglGetSwapIntervalEXT = NULL;

		this->gl_config.dll_handle = NULL;
		this->gl_config.driver_loaded = 0;
	}
}

/* Passing a NULL path means load pointers from the application */
int WIN_GL_LoadLibrary(_THIS, const char* path) 
{
	HMODULE handle;

 	if ( gl_active ) {
 		SDL_SetError("OpenGL context already created");
 		return -1;
 	}

	if ( path == NULL ) {
		path = DEFAULT_GL_DRIVER_PATH;
	}
	handle = LoadLibrary(path);
	if ( handle == NULL ) {
		SDL_SetError("Could not load OpenGL library");
		return -1;
	}

	/* Unload the old driver and reset the pointers */
	WIN_GL_UnloadLibrary(this);

	/* Load new function pointers */
	SDL_memset(this->gl_data, 0, sizeof(*this->gl_data));
	this->gl_data->wglGetProcAddress = (void * (WINAPI *)(const char *))
		GetProcAddress(handle, "wglGetProcAddress");
	this->gl_data->wglCreateContext = (HGLRC (WINAPI *)(HDC))
		GetProcAddress(handle, "wglCreateContext");
	this->gl_data->wglDeleteContext = (BOOL (WINAPI *)(HGLRC))
		GetProcAddress(handle, "wglDeleteContext");
	this->gl_data->wglMakeCurrent = (BOOL (WINAPI *)(HDC, HGLRC))
		GetProcAddress(handle, "wglMakeCurrent");
	this->gl_data->wglSwapIntervalEXT = (void (WINAPI *)(int))
		GetProcAddress(handle, "wglSwapIntervalEXT");
	this->gl_data->wglGetSwapIntervalEXT = (int (WINAPI *)(void))
		GetProcAddress(handle, "wglGetSwapIntervalEXT");

	if ( (this->gl_data->wglGetProcAddress == NULL) ||
	     (this->gl_data->wglCreateContext == NULL) ||
	     (this->gl_data->wglDeleteContext == NULL) ||
	     (this->gl_data->wglMakeCurrent == NULL) ) {
		SDL_SetError("Could not retrieve OpenGL functions");
		FreeLibrary(handle);
		return -1;
	}

	this->gl_config.dll_handle = handle;
	SDL_strlcpy(this->gl_config.driver_path, path, SDL_arraysize(this->gl_config.driver_path));
	this->gl_config.driver_loaded = 1;
	return 0;
}

void *WIN_GL_GetProcAddress(_THIS, const char* proc)
{
	void *func;

	/* This is to pick up extensions */
	func = this->gl_data->wglGetProcAddress(proc);
	if ( ! func ) {
		/* This is probably a normal GL function */
		func = GetProcAddress(this->gl_config.dll_handle, proc);
	}
	return func;
}

#endif /* SDL_VIDEO_OPENGL */