/*
===========================================================================
Copyright (C) 1999-2005 Id Software, Inc.

This file is part of Quake III Arena source code.

Quake III Arena source code is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.

Quake III Arena source code 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with Quake III Arena source code; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/

#ifdef USE_LOCAL_HEADERS
#	include "SDL.h"
#else
#	include <SDL.h>
#endif

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include "../renderercommon/tr_common.h"
#include "../sys/sys_local.h"
#include "sdl_icon.h"

typedef enum
{
	RSERR_OK,

	RSERR_INVALID_FULLSCREEN,
	RSERR_INVALID_MODE,

	RSERR_UNKNOWN
} rserr_t;

SDL_Window *SDL_window = NULL;
static SDL_GLContext SDL_glContext = NULL;

cvar_t *r_allowSoftwareGL; // Don't abort out if a hardware visual can't be obtained
cvar_t *r_allowResize; // make window resizable
cvar_t *r_centerWindow;
cvar_t *r_sdlDriver;

void (APIENTRYP qglActiveTextureARB) (GLenum texture);
void (APIENTRYP qglClientActiveTextureARB) (GLenum texture);
void (APIENTRYP qglMultiTexCoord2fARB) (GLenum target, GLfloat s, GLfloat t);

void (APIENTRYP qglLockArraysEXT) (GLint first, GLsizei count);
void (APIENTRYP qglUnlockArraysEXT) (void);

/*
===============
GLimp_Shutdown
===============
*/
void GLimp_Shutdown( void )
{
	ri.IN_Shutdown();

	SDL_QuitSubSystem( SDL_INIT_VIDEO );
}

/*
===============
GLimp_Minimize

Minimize the game so that user is back at the desktop
===============
*/
void GLimp_Minimize( void )
{
	SDL_MinimizeWindow( SDL_window );
}


/*
===============
GLimp_LogComment
===============
*/
void GLimp_LogComment( char *comment )
{
}

/*
===============
GLimp_CompareModes
===============
*/
static int GLimp_CompareModes( const void *a, const void *b )
{
	const float ASPECT_EPSILON = 0.001f;
	SDL_Rect *modeA = (SDL_Rect *)a;
	SDL_Rect *modeB = (SDL_Rect *)b;
	float aspectA = (float)modeA->w / (float)modeA->h;
	float aspectB = (float)modeB->w / (float)modeB->h;
	int areaA = modeA->w * modeA->h;
	int areaB = modeB->w * modeB->h;
	float aspectDiffA = fabs( aspectA - displayAspect );
	float aspectDiffB = fabs( aspectB - displayAspect );
	float aspectDiffsDiff = aspectDiffA - aspectDiffB;

	if( aspectDiffsDiff > ASPECT_EPSILON )
		return 1;
	else if( aspectDiffsDiff < -ASPECT_EPSILON )
		return -1;
	else
		return areaA - areaB;
}


/*
===============
GLimp_DetectAvailableModes
===============
*/
static void GLimp_DetectAvailableModes(void)
{
	int i, j;
	char buf[ MAX_STRING_CHARS ] = { 0 };
	int numSDLModes;
	SDL_Rect *modes;
	int numModes = 0;

	SDL_DisplayMode windowMode;
	int display = SDL_GetWindowDisplayIndex( SDL_window );
	if( display < 0 )
	{
		ri.Printf( PRINT_WARNING, "Couldn't get window display index, no resolutions detected: %s\n", SDL_GetError() );
		return;
	}
	numSDLModes = SDL_GetNumDisplayModes( display );

	if( SDL_GetWindowDisplayMode( SDL_window, &windowMode ) < 0 || numSDLModes <= 0 )
	{
		ri.Printf( PRINT_WARNING, "Couldn't get window display mode, no resolutions detected: %s\n", SDL_GetError() );
		return;
	}

	modes = SDL_calloc( (size_t)numSDLModes, sizeof( SDL_Rect ) );
	if ( !modes )
	{
		ri.Error( ERR_FATAL, "Out of memory" );
	}

	for( i = 0; i < numSDLModes; i++ )
	{
		SDL_DisplayMode mode;

		if( SDL_GetDisplayMode( display, i, &mode ) < 0 )
			continue;

		if( !mode.w || !mode.h )
		{
			ri.Printf( PRINT_ALL, "Display supports any resolution\n" );
			SDL_free( modes );
			return;
		}

		if( windowMode.format != mode.format )
			continue;

		// SDL can give the same resolution with different refresh rates.
		// Only list resolution once.
		for( j = 0; j < numModes; j++ )
		{
			if( mode.w == modes[ j ].w && mode.h == modes[ j ].h )
				break;
		}

		if( j != numModes )
			continue;

		modes[ numModes ].w = mode.w;
		modes[ numModes ].h = mode.h;
		numModes++;
	}

	if( numModes > 1 )
		qsort( modes, numModes, sizeof( SDL_Rect ), GLimp_CompareModes );

	for( i = 0; i < numModes; i++ )
	{
		const char *newModeString = va( "%ux%u ", modes[ i ].w, modes[ i ].h );

		if( strlen( newModeString ) < (int)sizeof( buf ) - strlen( buf ) )
			Q_strcat( buf, sizeof( buf ), newModeString );
		else
			ri.Printf( PRINT_WARNING, "Skipping mode %ux%u, buffer too small\n", modes[ i ].w, modes[ i ].h );
	}

	if( *buf )
	{
		buf[ strlen( buf ) - 1 ] = 0;
		ri.Printf( PRINT_ALL, "Available modes: '%s'\n", buf );
		ri.Cvar_Set( "r_availableModes", buf );
	}
	SDL_free( modes );
}

/*
===============
GLimp_SetMode
===============
*/
static int GLimp_SetMode(int mode, qboolean fullscreen, qboolean noborder)
{
	const char *glstring;
	int perChannelColorBits;
	int colorBits, depthBits, stencilBits;
	int samples;
	int i = 0;
	SDL_Surface *icon = NULL;
	Uint32 flags = SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL;
	SDL_DisplayMode desktopMode;
	int display = 0;
	int x = SDL_WINDOWPOS_UNDEFINED, y = SDL_WINDOWPOS_UNDEFINED;

	ri.Printf( PRINT_ALL, "Initializing OpenGL display\n");

	if ( r_allowResize->integer )
		flags |= SDL_WINDOW_RESIZABLE;

#ifdef USE_ICON
	icon = SDL_CreateRGBSurfaceFrom(
			(void *)CLIENT_WINDOW_ICON.pixel_data,
			CLIENT_WINDOW_ICON.width,
			CLIENT_WINDOW_ICON.height,
			CLIENT_WINDOW_ICON.bytes_per_pixel * 8,
			CLIENT_WINDOW_ICON.bytes_per_pixel * CLIENT_WINDOW_ICON.width,
#ifdef Q3_LITTLE_ENDIAN
			0x000000FF, 0x0000FF00, 0x00FF0000, 0xFF000000
#else
			0xFF000000, 0x00FF0000, 0x0000FF00, 0x000000FF
#endif
			);
#endif

	// If a window exists, note its display index
	if( SDL_window != NULL )
	{
		display = SDL_GetWindowDisplayIndex( SDL_window );
		if( display < 0 )
		{
			ri.Printf( PRINT_DEVELOPER, "SDL_GetWindowDisplayIndex() failed: %s\n", SDL_GetError() );
		}
	}

	if( display >= 0 && SDL_GetDesktopDisplayMode( display, &desktopMode ) == 0 )
	{
		displayAspect = (float)desktopMode.w / (float)desktopMode.h;

		ri.Printf( PRINT_ALL, "Display aspect: %.3f\n", displayAspect );
	}
	else
	{
		Com_Memset( &desktopMode, 0, sizeof( SDL_DisplayMode ) );

		ri.Printf( PRINT_ALL,
				"Cannot determine display aspect, assuming 1.333\n" );
	}

	ri.Printf (PRINT_ALL, "...setting mode %d:", mode );

	if (mode == -2)
	{
		// use desktop video resolution
		if( desktopMode.h > 0 )
		{
			glConfig.vidWidth = desktopMode.w;
			glConfig.vidHeight = desktopMode.h;
		}
		else
		{
			glConfig.vidWidth = 640;
			glConfig.vidHeight = 480;
			ri.Printf( PRINT_ALL,
					"Cannot determine display resolution, assuming 640x480\n" );
		}

		glConfig.windowAspect = (float)glConfig.vidWidth / (float)glConfig.vidHeight;
	}
	else if ( !R_GetModeInfo( &glConfig.vidWidth, &glConfig.vidHeight, &glConfig.windowAspect, mode ) )
	{
		ri.Printf( PRINT_ALL, " invalid mode\n" );
		return RSERR_INVALID_MODE;
	}
	ri.Printf( PRINT_ALL, " %d %d\n", glConfig.vidWidth, glConfig.vidHeight);

	// Center window
	if( r_centerWindow->integer && !fullscreen )
	{
		x = ( desktopMode.w / 2 ) - ( glConfig.vidWidth / 2 );
		y = ( desktopMode.h / 2 ) - ( glConfig.vidHeight / 2 );
	}

	// Destroy existing state if it exists
	if( SDL_glContext != NULL )
	{
		SDL_GL_DeleteContext( SDL_glContext );
		SDL_glContext = NULL;
	}

	if( SDL_window != NULL )
	{
		SDL_GetWindowPosition( SDL_window, &x, &y );
		ri.Printf( PRINT_DEVELOPER, "Existing window at %dx%d before being destroyed\n", x, y );
		SDL_DestroyWindow( SDL_window );
		SDL_window = NULL;
	}

	if( fullscreen )
	{
		flags |= SDL_WINDOW_FULLSCREEN;
		glConfig.isFullscreen = qtrue;
	}
	else
	{
		if( noborder )
			flags |= SDL_WINDOW_BORDERLESS;

		glConfig.isFullscreen = qfalse;
	}

	colorBits = r_colorbits->value;
	if ((!colorBits) || (colorBits >= 32))
		colorBits = 24;

	if (!r_depthbits->value)
		depthBits = 24;
	else
		depthBits = r_depthbits->value;

	stencilBits = r_stencilbits->value;
	samples = r_ext_multisample->value;

	for (i = 0; i < 16; i++)
	{
		int testColorBits, testDepthBits, testStencilBits;

		// 0 - default
		// 1 - minus colorBits
		// 2 - minus depthBits
		// 3 - minus stencil
		if ((i % 4) == 0 && i)
		{
			// one pass, reduce
			switch (i / 4)
			{
				case 2 :
					if (colorBits == 24)
						colorBits = 16;
					break;
				case 1 :
					if (depthBits == 24)
						depthBits = 16;
					else if (depthBits == 16)
						depthBits = 8;
				case 3 :
					if (stencilBits == 24)
						stencilBits = 16;
					else if (stencilBits == 16)
						stencilBits = 8;
			}
		}

		testColorBits = colorBits;
		testDepthBits = depthBits;
		testStencilBits = stencilBits;

		if ((i % 4) == 3)
		{ // reduce colorBits
			if (testColorBits == 24)
				testColorBits = 16;
		}

		if ((i % 4) == 2)
		{ // reduce depthBits
			if (testDepthBits == 24)
				testDepthBits = 16;
			else if (testDepthBits == 16)
				testDepthBits = 8;
		}

		if ((i % 4) == 1)
		{ // reduce stencilBits
			if (testStencilBits == 24)
				testStencilBits = 16;
			else if (testStencilBits == 16)
				testStencilBits = 8;
			else
				testStencilBits = 0;
		}

		if (testColorBits == 24)
			perChannelColorBits = 8;
		else
			perChannelColorBits = 4;

#ifdef __sgi /* Fix for SGIs grabbing too many bits of color */
		if (perChannelColorBits == 4)
			perChannelColorBits = 0; /* Use minimum size for 16-bit color */

		/* Need alpha or else SGIs choose 36+ bit RGB mode */
		SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 1);
#endif

		SDL_GL_SetAttribute( SDL_GL_RED_SIZE, perChannelColorBits );
		SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, perChannelColorBits );
		SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, perChannelColorBits );
		SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, testDepthBits );
		SDL_GL_SetAttribute( SDL_GL_STENCIL_SIZE, testStencilBits );

		SDL_GL_SetAttribute( SDL_GL_MULTISAMPLEBUFFERS, samples ? 1 : 0 );
		SDL_GL_SetAttribute( SDL_GL_MULTISAMPLESAMPLES, samples );

		if(r_stereoEnabled->integer)
		{
			glConfig.stereoEnabled = qtrue;
			SDL_GL_SetAttribute(SDL_GL_STEREO, 1);
		}
		else
		{
			glConfig.stereoEnabled = qfalse;
			SDL_GL_SetAttribute(SDL_GL_STEREO, 0);
		}
		
		SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );

#if 0 // if multisampling is enabled on X11, this causes create window to fail.
		// If not allowing software GL, demand accelerated
		if( !r_allowSoftwareGL->integer )
			SDL_GL_SetAttribute( SDL_GL_ACCELERATED_VISUAL, 1 );
#endif

		if( ( SDL_window = SDL_CreateWindow( CLIENT_WINDOW_TITLE, x, y,
				glConfig.vidWidth, glConfig.vidHeight, flags ) ) == NULL )
		{
			ri.Printf( PRINT_DEVELOPER, "SDL_CreateWindow failed: %s\n", SDL_GetError( ) );
			continue;
		}

		if( fullscreen )
		{
			SDL_DisplayMode mode;

			switch( testColorBits )
			{
				case 16: mode.format = SDL_PIXELFORMAT_RGB565; break;
				case 24: mode.format = SDL_PIXELFORMAT_RGB24;  break;
				default: ri.Printf( PRINT_DEVELOPER, "testColorBits is %d, can't fullscreen\n", testColorBits ); continue;
			}

			mode.w = glConfig.vidWidth;
			mode.h = glConfig.vidHeight;
			mode.refresh_rate = glConfig.displayFrequency = ri.Cvar_VariableIntegerValue( "r_displayRefresh" );
			mode.driverdata = NULL;

			if( SDL_SetWindowDisplayMode( SDL_window, &mode ) < 0 )
			{
				ri.Printf( PRINT_DEVELOPER, "SDL_SetWindowDisplayMode failed: %s\n", SDL_GetError( ) );
				continue;
			}
		}

		SDL_SetWindowIcon( SDL_window, icon );

		if( ( SDL_glContext = SDL_GL_CreateContext( SDL_window ) ) == NULL )
		{
			ri.Printf( PRINT_DEVELOPER, "SDL_GL_CreateContext failed: %s\n", SDL_GetError( ) );
			continue;
		}

		qglClearColor( 0, 0, 0, 1 );
		qglClear( GL_COLOR_BUFFER_BIT );
		SDL_GL_SwapWindow( SDL_window );

		if( SDL_GL_SetSwapInterval( r_swapInterval->integer ) == -1 )
		{
			ri.Printf( PRINT_DEVELOPER, "SDL_GL_SetSwapInterval failed: %s\n", SDL_GetError( ) );
		}

		glConfig.colorBits = testColorBits;
		glConfig.depthBits = testDepthBits;
		glConfig.stencilBits = testStencilBits;

		ri.Printf( PRINT_ALL, "Using %d color bits, %d depth, %d stencil display.\n",
				glConfig.colorBits, glConfig.depthBits, glConfig.stencilBits );
		break;
	}

	SDL_FreeSurface( icon );

	if( !SDL_window )
	{
		ri.Printf( PRINT_ALL, "Couldn't get a visual\n" );
		return RSERR_INVALID_MODE;
	}

	GLimp_DetectAvailableModes();

	glstring = (char *) qglGetString (GL_RENDERER);
	ri.Printf( PRINT_ALL, "GL_RENDERER: %s\n", glstring );

	return RSERR_OK;
}

/*
===============
GLimp_StartDriverAndSetMode
===============
*/
static qboolean GLimp_StartDriverAndSetMode(int mode, qboolean fullscreen, qboolean noborder)
{
	rserr_t err;

	if (!SDL_WasInit(SDL_INIT_VIDEO))
	{
		const char *driverName;

		if (SDL_Init(SDL_INIT_VIDEO) != 0)
		{
			ri.Printf( PRINT_ALL, "SDL_Init( SDL_INIT_VIDEO ) FAILED (%s)\n", SDL_GetError());
			return qfalse;
		}

		driverName = SDL_GetCurrentVideoDriver( );
		ri.Printf( PRINT_ALL, "SDL using driver \"%s\"\n", driverName );
		ri.Cvar_Set( "r_sdlDriver", driverName );
	}

	if (fullscreen && ri.Cvar_VariableIntegerValue( "in_nograb" ) )
	{
		ri.Printf( PRINT_ALL, "Fullscreen not allowed with in_nograb 1\n");
		ri.Cvar_Set( "r_fullscreen", "0" );
		r_fullscreen->modified = qfalse;
		fullscreen = qfalse;
	}
	
	err = GLimp_SetMode(mode, fullscreen, noborder);

	switch ( err )
	{
		case RSERR_INVALID_FULLSCREEN:
			ri.Printf( PRINT_ALL, "...WARNING: fullscreen unavailable in this mode\n" );
			return qfalse;
		case RSERR_INVALID_MODE:
			ri.Printf( PRINT_ALL, "...WARNING: could not set the given mode (%d)\n", mode );
			return qfalse;
		default:
			break;
	}

	return qtrue;
}

static qboolean GLimp_HaveExtension(const char *ext)
{
	const char *ptr = Q_stristr( glConfig.extensions_string, ext );
	if (ptr == NULL)
		return qfalse;
	ptr += strlen(ext);
	return ((*ptr == ' ') || (*ptr == '\0'));  // verify it's complete string.
}


/*
===============
GLimp_InitExtensions
===============
*/
static void GLimp_InitExtensions( void )
{
	if ( !r_allowExtensions->integer )
	{
		ri.Printf( PRINT_ALL, "* IGNORING OPENGL EXTENSIONS *\n" );
		return;
	}

	ri.Printf( PRINT_ALL, "Initializing OpenGL extensions\n" );

	glConfig.textureCompression = TC_NONE;

	// GL_EXT_texture_compression_s3tc
	if ( GLimp_HaveExtension( "GL_ARB_texture_compression" ) &&
	     GLimp_HaveExtension( "GL_EXT_texture_compression_s3tc" ) )
	{
		if ( r_ext_compressed_textures->value )
		{
			glConfig.textureCompression = TC_S3TC_ARB;
			ri.Printf( PRINT_ALL, "...using GL_EXT_texture_compression_s3tc\n" );
		}
		else
		{
			ri.Printf( PRINT_ALL, "...ignoring GL_EXT_texture_compression_s3tc\n" );
		}
	}
	else
	{
		ri.Printf( PRINT_ALL, "...GL_EXT_texture_compression_s3tc not found\n" );
	}

	// GL_S3_s3tc ... legacy extension before GL_EXT_texture_compression_s3tc.
	if (glConfig.textureCompression == TC_NONE)
	{
		if ( GLimp_HaveExtension( "GL_S3_s3tc" ) )
		{
			if ( r_ext_compressed_textures->value )
			{
				glConfig.textureCompression = TC_S3TC;
				ri.Printf( PRINT_ALL, "...using GL_S3_s3tc\n" );
			}
			else
			{
				ri.Printf( PRINT_ALL, "...ignoring GL_S3_s3tc\n" );
			}
		}
		else
		{
			ri.Printf( PRINT_ALL, "...GL_S3_s3tc not found\n" );
		}
	}


	// GL_EXT_texture_env_add
	glConfig.textureEnvAddAvailable = qfalse;
	if ( GLimp_HaveExtension( "EXT_texture_env_add" ) )
	{
		if ( r_ext_texture_env_add->integer )
		{
			glConfig.textureEnvAddAvailable = qtrue;
			ri.Printf( PRINT_ALL, "...using GL_EXT_texture_env_add\n" );
		}
		else
		{
			glConfig.textureEnvAddAvailable = qfalse;
			ri.Printf( PRINT_ALL, "...ignoring GL_EXT_texture_env_add\n" );
		}
	}
	else
	{
		ri.Printf( PRINT_ALL, "...GL_EXT_texture_env_add not found\n" );
	}

	// GL_ARB_multitexture
	qglMultiTexCoord2fARB = NULL;
	qglActiveTextureARB = NULL;
	qglClientActiveTextureARB = NULL;
	if ( GLimp_HaveExtension( "GL_ARB_multitexture" ) )
	{
		if ( r_ext_multitexture->value )
		{
			qglMultiTexCoord2fARB = SDL_GL_GetProcAddress( "glMultiTexCoord2fARB" );
			qglActiveTextureARB = SDL_GL_GetProcAddress( "glActiveTextureARB" );
			qglClientActiveTextureARB = SDL_GL_GetProcAddress( "glClientActiveTextureARB" );

			if ( qglActiveTextureARB )
			{
				GLint glint = 0;
				qglGetIntegerv( GL_MAX_TEXTURE_UNITS_ARB, &glint );
				glConfig.numTextureUnits = (int) glint;
				if ( glConfig.numTextureUnits > 1 )
				{
					ri.Printf( PRINT_ALL, "...using GL_ARB_multitexture\n" );
				}
				else
				{
					qglMultiTexCoord2fARB = NULL;
					qglActiveTextureARB = NULL;
					qglClientActiveTextureARB = NULL;
					ri.Printf( PRINT_ALL, "...not using GL_ARB_multitexture, < 2 texture units\n" );
				}
			}
		}
		else
		{
			ri.Printf( PRINT_ALL, "...ignoring GL_ARB_multitexture\n" );
		}
	}
	else
	{
		ri.Printf( PRINT_ALL, "...GL_ARB_multitexture not found\n" );
	}

	// GL_EXT_compiled_vertex_array
	if ( GLimp_HaveExtension( "GL_EXT_compiled_vertex_array" ) )
	{
		if ( r_ext_compiled_vertex_array->value )
		{
			ri.Printf( PRINT_ALL, "...using GL_EXT_compiled_vertex_array\n" );
			qglLockArraysEXT = ( void ( APIENTRY * )( GLint, GLint ) ) SDL_GL_GetProcAddress( "glLockArraysEXT" );
			qglUnlockArraysEXT = ( void ( APIENTRY * )( void ) ) SDL_GL_GetProcAddress( "glUnlockArraysEXT" );
			if (!qglLockArraysEXT || !qglUnlockArraysEXT)
			{
				ri.Error (ERR_FATAL, "bad getprocaddress");
			}
		}
		else
		{
			ri.Printf( PRINT_ALL, "...ignoring GL_EXT_compiled_vertex_array\n" );
		}
	}
	else
	{
		ri.Printf( PRINT_ALL, "...GL_EXT_compiled_vertex_array not found\n" );
	}

	textureFilterAnisotropic = qfalse;
	if ( GLimp_HaveExtension( "GL_EXT_texture_filter_anisotropic" ) )
	{
		if ( r_ext_texture_filter_anisotropic->integer ) {
			qglGetIntegerv( GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, (GLint *)&maxAnisotropy );
			if ( maxAnisotropy <= 0 ) {
				ri.Printf( PRINT_ALL, "...GL_EXT_texture_filter_anisotropic not properly supported!\n" );
				maxAnisotropy = 0;
			}
			else
			{
				ri.Printf( PRINT_ALL, "...using GL_EXT_texture_filter_anisotropic (max: %i)\n", maxAnisotropy );
				textureFilterAnisotropic = qtrue;
			}
		}
		else
		{
			ri.Printf( PRINT_ALL, "...ignoring GL_EXT_texture_filter_anisotropic\n" );
		}
	}
	else
	{
		ri.Printf( PRINT_ALL, "...GL_EXT_texture_filter_anisotropic not found\n" );
	}
}

#define R_MODE_FALLBACK 3 // 640 * 480

/*
===============
GLimp_Init

This routine is responsible for initializing the OS specific portions
of OpenGL
===============
*/
void GLimp_Init( void )
{
	ri.Printf( PRINT_DEVELOPER, "Glimp_Init( )\n" );

	r_allowSoftwareGL = ri.Cvar_Get( "r_allowSoftwareGL", "0", CVAR_LATCH );
	r_sdlDriver = ri.Cvar_Get( "r_sdlDriver", "", CVAR_ROM );
	r_allowResize = ri.Cvar_Get( "r_allowResize", "0", CVAR_ARCHIVE | CVAR_LATCH );
	r_centerWindow = ri.Cvar_Get( "r_centerWindow", "0", CVAR_ARCHIVE | CVAR_LATCH );

	if( ri.Cvar_VariableIntegerValue( "com_abnormalExit" ) )
	{
		ri.Cvar_Set( "r_mode", va( "%d", R_MODE_FALLBACK ) );
		ri.Cvar_Set( "r_fullscreen", "0" );
		ri.Cvar_Set( "r_centerWindow", "0" );
		ri.Cvar_Set( "com_abnormalExit", "0" );
	}

	ri.Sys_GLimpInit( );

	// Create the window and set up the context
	if(GLimp_StartDriverAndSetMode(r_mode->integer, r_fullscreen->integer, r_noborder->integer))
		goto success;

	// Try again, this time in a platform specific "safe mode"
	ri.Sys_GLimpSafeInit( );

	if(GLimp_StartDriverAndSetMode(r_mode->integer, r_fullscreen->integer, qfalse))
		goto success;

	// Finally, try the default screen resolution
	if( r_mode->integer != R_MODE_FALLBACK )
	{
		ri.Printf( PRINT_ALL, "Setting r_mode %d failed, falling back on r_mode %d\n",
				r_mode->integer, R_MODE_FALLBACK );

		if(GLimp_StartDriverAndSetMode(R_MODE_FALLBACK, qfalse, qfalse))
			goto success;
	}

	// Nothing worked, give up
	ri.Error( ERR_FATAL, "GLimp_Init() - could not load OpenGL subsystem" );

success:
	// These values force the UI to disable driver selection
	glConfig.driverType = GLDRV_ICD;
	glConfig.hardwareType = GLHW_GENERIC;

	// Only using SDL_SetWindowBrightness to determine if hardware gamma is supported
	glConfig.deviceSupportsGamma = !r_ignorehwgamma->integer &&
		SDL_SetWindowBrightness( SDL_window, 1.0f ) >= 0;

	// get our config strings
	Q_strncpyz( glConfig.vendor_string, (char *) qglGetString (GL_VENDOR), sizeof( glConfig.vendor_string ) );
	Q_strncpyz( glConfig.renderer_string, (char *) qglGetString (GL_RENDERER), sizeof( glConfig.renderer_string ) );
	if (*glConfig.renderer_string && glConfig.renderer_string[strlen(glConfig.renderer_string) - 1] == '\n')
		glConfig.renderer_string[strlen(glConfig.renderer_string) - 1] = 0;
	Q_strncpyz( glConfig.version_string, (char *) qglGetString (GL_VERSION), sizeof( glConfig.version_string ) );
	Q_strncpyz( glConfig.extensions_string, (char *) qglGetString (GL_EXTENSIONS), sizeof( glConfig.extensions_string ) );

	// initialize extensions
	GLimp_InitExtensions( );

	ri.Cvar_Get( "r_availableModes", "", CVAR_ROM );

	// This depends on SDL_INIT_VIDEO, hence having it here
	ri.IN_Init( SDL_window );
}


/*
===============
GLimp_EndFrame

Responsible for doing a swapbuffers
===============
*/
void GLimp_EndFrame( void )
{
	// don't flip if drawing to front buffer
	if ( Q_stricmp( r_drawBuffer->string, "GL_FRONT" ) != 0 )
	{
		SDL_GL_SwapWindow( SDL_window );
	}

	if( r_fullscreen->modified )
	{
		int         fullscreen;
		qboolean    needToToggle;
		qboolean    sdlToggled = qfalse;

		// Find out the current state
		fullscreen = !!( SDL_GetWindowFlags( SDL_window ) & SDL_WINDOW_FULLSCREEN );

		if( r_fullscreen->integer && ri.Cvar_VariableIntegerValue( "in_nograb" ) )
		{
			ri.Printf( PRINT_ALL, "Fullscreen not allowed with in_nograb 1\n");
			ri.Cvar_Set( "r_fullscreen", "0" );
			r_fullscreen->modified = qfalse;
		}

		// Is the state we want different from the current state?
		needToToggle = !!r_fullscreen->integer != fullscreen;

		if( needToToggle )
		{
			sdlToggled = SDL_SetWindowFullscreen( SDL_window, r_fullscreen->integer ) >= 0;

			// SDL_WM_ToggleFullScreen didn't work, so do it the slow way
			if( !sdlToggled )
				ri.Cmd_ExecuteText(EXEC_APPEND, "vid_restart\n");

			ri.IN_Restart( );
		}

		r_fullscreen->modified = qfalse;
	}
}