/*
===========================================================================
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
===========================================================================
*/
/*
** WIN_GLIMP.C
**
** This file contains ALL Win32 specific stuff having to do with the
** OpenGL refresh.  When a port is being made the following functions
** must be implemented by the port:
**
** GLimp_EndFrame
** GLimp_Init
** GLimp_Shutdown
**
** Note that the GLW_xxx functions are Windows specific GL-subsystem
** related functions that are relevant ONLY to win_glimp.c
*/

#if _MSC_VER
#pragma warning (disable: 4996) // deprecated ZOMGOVERRUN! nannywhine
#endif

#include "../renderer/tr_local.h"
#include "resource.h"
#include "glw_win.h"
#include "wglext.h"
#include "win_local.h"


#define TRY_PFD_SUCCESS		0
#define TRY_PFD_FAIL_SOFT	1
#define TRY_PFD_FAIL_HARD	2

glwstate_t glw_state;


/*
** ChoosePFD
**
** Helper function that replaces ChoosePixelFormat.
*/
#define MAX_PFDS 256

static int GLW_ChoosePFD( HDC hDC, PIXELFORMATDESCRIPTOR *pPFD )
{
	PIXELFORMATDESCRIPTOR pfds[MAX_PFDS+1];
	int maxPFD = 0;
	int i;
	int bestMatch = 0;

	ri.Printf( PRINT_DEVELOPER, "...GLW_ChoosePFD( %d, %d, %d )\n", ( int ) pPFD->cColorBits, ( int ) pPFD->cDepthBits, ( int ) pPFD->cStencilBits );

	maxPFD = DescribePixelFormat( hDC, 1, sizeof( PIXELFORMATDESCRIPTOR ), &pfds[0] );
	if ( maxPFD > MAX_PFDS )
	{
		ri.Printf( PRINT_WARNING, "...numPFDs > MAX_PFDS (%d > %d)\n", maxPFD, MAX_PFDS );
		maxPFD = MAX_PFDS;
	}

	ri.Printf( PRINT_DEVELOPER, "...%d PFDs found\n", maxPFD - 1 );

	// grab information
	for ( i = 1; i <= maxPFD; i++ )
	{
		DescribePixelFormat( hDC, i, sizeof( PIXELFORMATDESCRIPTOR ), &pfds[i] );
	}

	// look for a best match
	for ( i = 1; i <= maxPFD; i++ )
	{
		//
		// make sure this has hardware acceleration
		//
		if ( ( pfds[i].dwFlags & PFD_GENERIC_FORMAT ) != 0 ) 
		{
			continue;
		}

		// verify pixel type
		if ( pfds[i].iPixelType != PFD_TYPE_RGBA )
		{
			if ( r_verbose->integer )
			{
				ri.Printf( PRINT_DEVELOPER, "...PFD %d rejected, not RGBA\n", i );
			}
			continue;
		}

		// verify proper flags
		if ( ( ( pfds[i].dwFlags & pPFD->dwFlags ) & pPFD->dwFlags ) != pPFD->dwFlags ) 
		{
			if ( r_verbose->integer )
			{
				ri.Printf( PRINT_DEVELOPER, "...PFD %d rejected, improper flags (%x instead of %x)\n", i, pfds[i].dwFlags, pPFD->dwFlags );
			}
			continue;
		}

		// verify enough bits
		if ( pfds[i].cDepthBits < 15 )
		{
			continue;
		}
		if ( ( pfds[i].cStencilBits < 4 ) && ( pPFD->cStencilBits > 0 ) )
		{
			continue;
		}

		//
		// selection criteria (in order of priority):
		// 
		//  PFD_STEREO
		//  colorBits
		//  depthBits
		//  stencilBits
		//
		if ( bestMatch )
		{
			// check stereo
			if ( ( pfds[i].dwFlags & PFD_STEREO ) && ( !( pfds[bestMatch].dwFlags & PFD_STEREO ) ) && ( pPFD->dwFlags & PFD_STEREO ) )
			{
				bestMatch = i;
				continue;
			}
			
			if ( !( pfds[i].dwFlags & PFD_STEREO ) && ( pfds[bestMatch].dwFlags & PFD_STEREO ) && ( pPFD->dwFlags & PFD_STEREO ) )
			{
				bestMatch = i;
				continue;
			}

			// check color
			if ( pfds[bestMatch].cColorBits != pPFD->cColorBits )
			{
				// prefer perfect match
				if ( pfds[i].cColorBits == pPFD->cColorBits )
				{
					bestMatch = i;
					continue;
				}
				// otherwise if this PFD has more bits than our best, use it
				else if ( pfds[i].cColorBits > pfds[bestMatch].cColorBits )
				{
					bestMatch = i;
					continue;
				}
			}

			// check depth
			if ( pfds[bestMatch].cDepthBits != pPFD->cDepthBits )
			{
				// prefer perfect match
				if ( pfds[i].cDepthBits == pPFD->cDepthBits )
				{
					bestMatch = i;
					continue;
				}
				// otherwise if this PFD has more bits than our best, use it
				else if ( pfds[i].cDepthBits > pfds[bestMatch].cDepthBits )
				{
					bestMatch = i;
					continue;
				}
			}

			// check stencil
			if ( pfds[bestMatch].cStencilBits != pPFD->cStencilBits )
			{
				// prefer perfect match
				if ( pfds[i].cStencilBits == pPFD->cStencilBits )
				{
					bestMatch = i;
					continue;
				}
				// otherwise if this PFD has more bits than our best, use it
				else if ( ( pfds[i].cStencilBits > pfds[bestMatch].cStencilBits ) && 
					 ( pPFD->cStencilBits > 0 ) )
				{
					bestMatch = i;
					continue;
				}
			}
		}
		else
		{
			bestMatch = i;
		}
	}

	if ( !bestMatch )
		return 0;

	if ( pfds[bestMatch].dwFlags & (PFD_GENERIC_FORMAT | PFD_GENERIC_ACCELERATED) ) {
		ri.Printf( PRINT_ALL, "...no OpenGL ICD found\n" );
		return 0;
	}

	*pPFD = pfds[bestMatch];

	return bestMatch;
}

/*
** void GLW_CreatePFD
**
** Helper function zeros out then fills in a PFD
*/
static void GLW_CreatePFD( PIXELFORMATDESCRIPTOR *pPFD, int colorbits, int depthbits, int stencilbits, qbool stereo )
{
	PIXELFORMATDESCRIPTOR src = 
	{
		sizeof(PIXELFORMATDESCRIPTOR),	// size of this pfd
		1,								// version number
		PFD_DRAW_TO_WINDOW |			// support window
		PFD_SUPPORT_OPENGL |			// support OpenGL
		PFD_DOUBLEBUFFER,				// double buffered
		PFD_TYPE_RGBA,					// RGBA type
		24,								// 24-bit color depth
		0, 0, 0, 0, 0, 0,				// color bits ignored
		0,								// no alpha buffer
		0,								// shift bit ignored
		0,								// no accumulation buffer
		0, 0, 0, 0, 					// accum bits ignored
		24,								// 24-bit z-buffer
		8,								// 8-bit stencil buffer
		0,								// no auxiliary buffer
		PFD_MAIN_PLANE,					// main layer
		0,								// reserved
		0, 0, 0							// layer masks ignored
	};

	src.cColorBits = (BYTE)colorbits;
	src.cDepthBits = (BYTE)depthbits;
	src.cStencilBits = (BYTE)stencilbits;

	if ( stereo )
	{
		ri.Printf( PRINT_ALL, "...attempting to use stereo\n" );
		src.dwFlags |= PFD_STEREO;
		glConfig.stereoEnabled = qtrue;
	}
	else
	{
		glConfig.stereoEnabled = qfalse;
	}

	*pPFD = src;
}

static int GLW_MakeContext( PIXELFORMATDESCRIPTOR *pPFD )
{
	int pixelformat;

	//
	// don't putz around with pixelformat if it's already set (e.g. this is a soft
	// reset of the graphics system)
	//
	if ( !glw_state.pixelFormatSet )
	{
		//
		// choose, set, and describe our desired pixel format.  If we're
		// using a minidriver then we need to bypass the GDI functions,
		// otherwise use the GDI functions.
		//
		if (glw_state.nPendingPF)
			pixelformat = glw_state.nPendingPF;
		else
		if ( ( pixelformat = GLW_ChoosePFD( glw_state.hDC, pPFD ) ) == 0 )
		{
			ri.Printf( PRINT_ALL, "...GLW_ChoosePFD failed\n");
			return TRY_PFD_FAIL_SOFT;
		}
		ri.Printf( PRINT_DEVELOPER, "...PIXELFORMAT %d selected\n", pixelformat );

		DescribePixelFormat( glw_state.hDC, pixelformat, sizeof( *pPFD ), pPFD );

		if ( SetPixelFormat( glw_state.hDC, pixelformat, pPFD ) == FALSE )
		{
			ri.Printf( PRINT_ALL, "...SetPixelFormat failed\n", glw_state.hDC );
			return TRY_PFD_FAIL_SOFT;
		}

		glw_state.pixelFormatSet = qtrue;
	}

	//
	// startup the OpenGL subsystem by creating a context and making it current
	//
	if ( !glw_state.hGLRC )
	{
		if ( ( glw_state.hGLRC = qwglCreateContext( glw_state.hDC ) ) == 0 )
		{
			ri.Printf( PRINT_ALL, "...GL context creation failure\n" );
			return TRY_PFD_FAIL_HARD;
		}
		ri.Printf( PRINT_DEVELOPER, "...GL context created\n" );

		if ( !qwglMakeCurrent( glw_state.hDC, glw_state.hGLRC ) )
		{
			qwglDeleteContext( glw_state.hGLRC );
			glw_state.hGLRC = NULL;
			ri.Printf( PRINT_ALL, "...GL context creation currency failure\n" );
			return TRY_PFD_FAIL_HARD;
		}
		ri.Printf( PRINT_DEVELOPER, "...GL context creation made current\n" );
	}

	return TRY_PFD_SUCCESS;
}


/*
** - get a DC if one doesn't exist
** - create an HGLRC if one doesn't exist
*/
static qbool GLW_InitDriver( int colorbits )
{
	int		tpfd;
	int		depthbits, stencilbits;
	static PIXELFORMATDESCRIPTOR pfd;		// save between frames since 'tr' gets cleared

	ri.Printf( PRINT_DEVELOPER, "Initializing OpenGL driver\n" );

	//
	// get a DC for our window if we don't already have one allocated
	//
	if ( glw_state.hDC == NULL )
	{
		if ( ( glw_state.hDC = GetDC( g_wv.hWnd ) ) == NULL )
		{
			ri.Printf( PRINT_ALL, "...Get DC failed\n" );
			return qfalse;
		}
		ri.Printf( PRINT_DEVELOPER, "...Get DC succeeded\n" );
	}

	if ( colorbits == 0 )
	{
		colorbits = glw_state.desktopBPP;
	}

	//
	// implicitly assume Z-buffer depth == desktop color depth
	//
	if ( r_depthbits->integer == 0 ) {
		if ( colorbits > 16 ) {
			depthbits = 24;
		} else {
			depthbits = 16;
		}
	} else {
		depthbits = r_depthbits->integer;
	}

	//
	// do not allow stencil if Z-buffer depth likely won't contain it
	//
	stencilbits = r_stencilbits->integer;
	if ( depthbits < 24 )
	{
		stencilbits = 0;
	}

	//
	// make two attempts to set the PIXELFORMAT
	//

	//
	// first attempt: r_colorbits, depthbits, and r_stencilbits
	//
	if ( !glw_state.pixelFormatSet )
	{
		GLW_CreatePFD( &pfd, colorbits, depthbits, stencilbits, (qbool)r_stereo->integer );
		if ( ( tpfd = GLW_MakeContext( &pfd ) ) != TRY_PFD_SUCCESS )
		{
			if ( tpfd == TRY_PFD_FAIL_HARD )
			{
				ri.Printf( PRINT_WARNING, "...failed hard\n" );
				return qfalse;
			}

			//
			// punt if we've already tried the desktop bit depth and no stencil bits
			//
			if ( ( r_colorbits->integer == glw_state.desktopBPP ) && !stencilbits )
			{
				ReleaseDC( g_wv.hWnd, glw_state.hDC );
				glw_state.hDC = NULL;
				ri.Printf( PRINT_ALL, "...failed to find an appropriate PIXELFORMAT\n" );
				return qfalse;
			}

			//
			// second attempt: desktop's color bits and no stencil
			//
			if ( colorbits > glw_state.desktopBPP )
				colorbits = glw_state.desktopBPP;

			GLW_CreatePFD( &pfd, colorbits, depthbits, 0, (qbool)r_stereo->integer );
			if ( GLW_MakeContext( &pfd ) != TRY_PFD_SUCCESS )
			{
				if ( glw_state.hDC )
				{
					ReleaseDC( g_wv.hWnd, glw_state.hDC );
					glw_state.hDC = NULL;
				}
				ri.Printf( PRINT_ALL, "...failed to find an appropriate PIXELFORMAT\n" );
				return qfalse;
			}
		}

		// report if stereo is desired but unavailable
		//
		if ( r_stereo->integer && !( pfd.dwFlags & PFD_STEREO ) )
		{
			ri.Printf( PRINT_ALL, "...failed to select stereo pixel format\n" );
			glConfig.stereoEnabled = qfalse;
		}
	}

	// store PFD specifics
	//
	glConfig.colorBits = ( int ) pfd.cColorBits;
	glConfig.depthBits = ( int ) pfd.cDepthBits;
	glConfig.stencilBits = ( int ) pfd.cStencilBits;

	return qtrue;
}


// responsible for creating the Win32 window and initializing the OpenGL driver.

static qbool GLW_CreateWindow( int width, int height, int colorbits )
{
	static qbool s_classRegistered = qfalse;

	if ( !s_classRegistered )
	{
		WNDCLASS wc;
		memset( &wc, 0, sizeof( wc ) );

		wc.style         = CS_OWNDC;
		wc.lpfnWndProc   = MainWndProc;
		wc.cbClsExtra    = 0;
		wc.cbWndExtra    = 0;
		wc.hInstance     = g_wv.hInstance;
		wc.hIcon         = LoadIcon( g_wv.hInstance, MAKEINTRESOURCE(IDI_ICON1));
		wc.hCursor       = LoadCursor (NULL,IDC_ARROW);
		wc.hbrBackground = (HBRUSH)COLOR_GRAYTEXT;
		wc.lpszMenuName  = 0;
		wc.lpszClassName = CLIENT_WINDOW_TITLE;

		if ( !RegisterClass( &wc ) )
			ri.Error( ERR_FATAL, "GLW_CreateWindow: could not register window class" );

		s_classRegistered = qtrue;
		ri.Printf( PRINT_DEVELOPER, "...registered window class\n" );
	}


	RECT r;
	int x, y, w, h;

	//
	// create the HWND if one does not already exist
	//
	if ( !g_wv.hWnd )
	{
		//
		// compute width and height
		//
		r.left = 0;
		r.top = 0;
		r.right  = width;
		r.bottom = height;

		int style = WS_VISIBLE | WS_SYSMENU;
		int exstyle;

		if ( glInfo.isFullscreen )
		{
			style |= WS_POPUP;
			exstyle = WS_EX_TOPMOST;
		}
		else
		{
			style |= WS_OVERLAPPED | WS_BORDER | WS_CAPTION;
			exstyle = 0;
			AdjustWindowRect( &r, style, FALSE );
		}

		w = r.right - r.left;
		h = r.bottom - r.top;

		if ( glInfo.isFullscreen )
		{
			x = 0;
			y = 0;
		}
		else
		{
			const cvar_t* vid_xpos = ri.Cvar_Get( "vid_xpos", "", 0 );
			const cvar_t* vid_ypos = ri.Cvar_Get( "vid_ypos", "", 0 );
			x = vid_xpos->integer;
			y = vid_ypos->integer;
		}

		g_wv.hWnd = CreateWindowEx( exstyle, CLIENT_WINDOW_TITLE, CLIENT_WINDOW_TITLE, style,
				x, y, w, h, NULL, NULL, g_wv.hInstance, NULL );

		if ( !g_wv.hWnd )
			ri.Error( ERR_FATAL, "GLW_CreateWindow() - Couldn't create window" );

		ShowWindow( g_wv.hWnd, SW_SHOW );
		UpdateWindow( g_wv.hWnd );
		ri.Printf( PRINT_DEVELOPER, "...created window@%d,%d (%dx%d)\n", x, y, w, h );
	}
	else
	{
		ri.Printf( PRINT_DEVELOPER, "...window already present, CreateWindowEx skipped\n" );
	}

	if ( !GLW_InitDriver( colorbits ) )
	{
		ShowWindow( g_wv.hWnd, SW_HIDE );
		DestroyWindow( g_wv.hWnd );
		g_wv.hWnd = NULL;
		return qfalse;
	}

	SetForegroundWindow( g_wv.hWnd );
	SetFocus( g_wv.hWnd );

	return qtrue;
}


static qbool GLW_Fullscreen( DEVMODE& dm )
{
	int cds = ChangeDisplaySettings( &dm, CDS_FULLSCREEN );

	if (cds == DISP_CHANGE_SUCCESSFUL)
		return qtrue;

	ri.Printf( PRINT_ALL, "...CDS: %ix%i (C%i) failed: ", dm.dmPelsWidth, dm.dmPelsHeight, dm.dmBitsPerPel );

#define CDS_ERROR(x) case x: ri.Printf( PRINT_ALL, #x##"\n" ); break;
	switch (cds) {
		default:
			ri.Printf( PRINT_ALL, "unknown error %d\n", cds );
			break;
		CDS_ERROR( DISP_CHANGE_RESTART );
		CDS_ERROR( DISP_CHANGE_BADPARAM );
		CDS_ERROR( DISP_CHANGE_BADFLAGS );
		CDS_ERROR( DISP_CHANGE_FAILED );
		CDS_ERROR( DISP_CHANGE_BADMODE );
		CDS_ERROR( DISP_CHANGE_NOTUPDATED );
	}
#undef CDS_ERROR

	return qfalse;
}


// GL_multisample is SUCH a fucking mess  >:(

static void GLW_AttemptFSAA()
{
	static const float ar[] = { 0, 0 };
	// ignore r_xyzbits vars - FSAA requires 32-bit color, and anyone using it is implicitly on decent HW
	static int anAttributes[] = {
		WGL_DRAW_TO_WINDOW_ARB, GL_TRUE,
		WGL_SUPPORT_OPENGL_ARB, GL_TRUE,
		WGL_ACCELERATION_ARB, WGL_FULL_ACCELERATION_ARB,
		WGL_DOUBLE_BUFFER_ARB, GL_TRUE,
		WGL_COLOR_BITS_ARB, 32,
		WGL_ALPHA_BITS_ARB, 0,
		WGL_DEPTH_BITS_ARB, 24,
		WGL_STENCIL_BITS_ARB, 8,
		WGL_SAMPLE_BUFFERS_ARB, GL_TRUE,
		WGL_SAMPLES_ARB, 4,
		0, 0
	};

	qwglChoosePixelFormatARB = (PFNWGLCHOOSEPIXELFORMATARBPROC)qwglGetProcAddress( "wglChoosePixelFormatARB" );
	if (!r_ext_multisample->integer || !qwglChoosePixelFormatARB) {
		glDisable(GL_MULTISAMPLE_ARB);
		return;
	}

	int iPFD;
	UINT cPFD;
	anAttributes[19] = r_ext_multisample->integer;	// !!! UGH
	if (!qwglChoosePixelFormatARB(glw_state.hDC, anAttributes, ar, 1, &iPFD, &cPFD) || !cPFD)
		return;

	// now bounce the ENTIRE fucking subsytem thanks to WGL stupidity
	// we can't use GLimp_Shutdown() for this, because that does CDS poking that we don't want
	assert( glw_state.hGLRC && glw_state.hDC && g_wv.hWnd );

	qwglMakeCurrent( glw_state.hDC, NULL );

	if ( glw_state.hGLRC ) {
		qwglDeleteContext( glw_state.hGLRC );
		glw_state.hGLRC = NULL;
	}

	if ( glw_state.hDC ) {
		ReleaseDC( g_wv.hWnd, glw_state.hDC );
		glw_state.hDC = NULL;
	}

	if ( g_wv.hWnd ) {
		DestroyWindow( g_wv.hWnd );
		g_wv.hWnd = NULL;
	}

	ri.Printf( PRINT_ALL, "...enabling FSAA\n" );

	glw_state.nPendingPF = iPFD;
	glw_state.pixelFormatSet = qfalse;
	GLW_CreateWindow( glConfig.vidWidth, glConfig.vidHeight, glConfig.colorBits );
	glw_state.nPendingPF = 0;

	glEnable(GL_MULTISAMPLE_ARB);
}


static qbool GLW_SetMode( qbool cdsFullscreen )
{
	HDC hDC = GetDC( GetDesktopWindow() );
	glw_state.desktopBPP = GetDeviceCaps( hDC, BITSPIXEL );
	glw_state.desktopWidth = GetDeviceCaps( hDC, HORZRES );
	glw_state.desktopHeight = GetDeviceCaps( hDC, VERTRES );
	ReleaseDC( GetDesktopWindow(), hDC );

	glInfo.isFullscreen = cdsFullscreen;
	if ( !R_GetModeInfo( &glConfig.vidWidth, &glConfig.vidHeight, &glConfig.windowAspect ) ) {
		glConfig.vidWidth = glw_state.desktopWidth;
		glConfig.vidHeight = glw_state.desktopHeight;
		glConfig.windowAspect = (float)glConfig.vidWidth / glConfig.vidHeight;
		cdsFullscreen = qfalse;
	}
	//ri.Printf( PRINT_DEVELOPER, "...setting mode %dx%d %s\n", glConfig.vidWidth, glConfig.vidHeight, cdsFullscreen ? "FS" : "W" );

	DEVMODE dm;
	memset( &dm, 0, sizeof( dm ) );
	dm.dmSize = sizeof( dm );

	if (cdsFullscreen != glw_state.cdsFullscreen) {
		if (cdsFullscreen) {
			dm.dmPelsWidth  = glConfig.vidWidth;
			dm.dmPelsHeight = glConfig.vidHeight;
			dm.dmFields     = DM_PELSWIDTH | DM_PELSHEIGHT;

			if ( r_displayRefresh->integer ) {
				dm.dmDisplayFrequency = r_displayRefresh->integer;
				dm.dmFields |= DM_DISPLAYFREQUENCY;
			}

			if ( r_colorbits->integer ) {
				dm.dmBitsPerPel = r_colorbits->integer;
				dm.dmFields |= DM_BITSPERPEL;
			}

			glInfo.isFullscreen = qtrue;
			glw_state.cdsFullscreen = qtrue;

			if (!GLW_Fullscreen( dm )) {
				glInfo.isFullscreen = qfalse;
				glw_state.cdsFullscreen = qfalse;
			}
		}
		else
		{
			ChangeDisplaySettings( 0, 0 );
			glw_state.cdsFullscreen = qfalse;
		}
	}

	if (!GLW_CreateWindow( glConfig.vidWidth, glConfig.vidHeight, glConfig.colorBits ))
		return qfalse;

	if (EnumDisplaySettings( NULL, ENUM_CURRENT_SETTINGS, &dm ))
		glInfo.displayFrequency = dm.dmDisplayFrequency;

	GLW_AttemptFSAA();

	return qtrue;
}


static void GLW_InitExtensions()
{
	ri.Printf( PRINT_DEVELOPER, "Initializing OpenGL extensions\n" );

#define QGL_EXT(T, fn) q##fn = (T)qwglGetProcAddress( #fn ); \
	if (!q##fn) Com_Error( ERR_FATAL, "QGL_EXT: required extension "#fn" not found" );

	QGL_EXT( PFNGLLOCKARRAYSEXTPROC, glLockArraysEXT );
	QGL_EXT( PFNGLUNLOCKARRAYSEXTPROC, glUnlockArraysEXT );
	QGL_EXT( PFNGLACTIVETEXTUREARBPROC, glActiveTextureARB );
	QGL_EXT( PFNGLCLIENTACTIVETEXTUREARBPROC, glClientActiveTextureARB );

#undef QGL_EXT

	// WGL_EXT_swap_control
	qwglSwapIntervalEXT = ( BOOL (WINAPI *)(int)) qwglGetProcAddress( "wglSwapIntervalEXT" );
	if ( qwglSwapIntervalEXT )
	{
		ri.Printf( PRINT_DEVELOPER, "...using WGL_EXT_swap_control\n" );
		r_swapInterval->modified = qtrue;	// force a set next frame
	}
	else
	{
		ri.Printf( PRINT_DEVELOPER, "...WGL_EXT_swap_control not found\n" );
	}

	int maxAnisotropy = 0;
	if ( strstr( glConfig.extensions_string, "GL_EXT_texture_filter_anisotropic" ) )
	{
		if (r_ext_max_anisotropy->integer > 1) {
			qglGetIntegerv( GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &maxAnisotropy );
			if ( maxAnisotropy <= 0 ) {
				ri.Printf( PRINT_DEVELOPER, "...GL_EXT_texture_filter_anisotropic not properly supported!\n" );
				maxAnisotropy = 0;
			}
			else
			{
				ri.Printf( PRINT_DEVELOPER, "...using GL_EXT_texture_filter_anisotropic (max: %i)\n", maxAnisotropy );
			}
		}
		else
		{
			ri.Printf( PRINT_DEVELOPER, "...ignoring GL_EXT_texture_filter_anisotropic\n" );
		}
	}
	else
	{
		ri.Printf( PRINT_DEVELOPER, "...GL_EXT_texture_filter_anisotropic not found\n" );
	}
	Cvar_Set( "r_ext_max_anisotropy", va("%i", maxAnisotropy) );

}


static qbool GLW_LoadOpenGL()
{
	// only real GL implementations are acceptable
	const char* OPENGL_DRIVER_NAME = "opengl32";

	// load the driver and bind our function pointers to it
	if ( QGL_Init( OPENGL_DRIVER_NAME ) ) {
		// create the window and set up the context
		if ( GLW_SetMode( (qbool)r_fullscreen->integer ) ) {
			return qtrue;
		}
	}

	QGL_Shutdown();

	return qfalse;
}


void GLimp_EndFrame()
{
	if ( r_swapInterval->modified ) {
		r_swapInterval->modified = qfalse;

		if ( !glConfig.stereoEnabled && qwglSwapIntervalEXT ) {
			qwglSwapIntervalEXT( r_swapInterval->integer );
		}
	}

	// don't flip if drawing to front buffer
	if ( Q_stricmp( r_drawBuffer->string, "GL_FRONT" ) != 0 ) {
		SwapBuffers( glw_state.hDC );
	}
}


///////////////////////////////////////////////////////////////


static unsigned short s_oldHardwareGamma[3][256];


static void GLW_CheckHardwareGamma()
{
	glConfig.deviceSupportsGamma = qfalse;

	if (r_ignorehwgamma->integer)
		return;

	HDC hDC = GetDC( GetDesktopWindow() );
	glConfig.deviceSupportsGamma = (qbool)GetDeviceGammaRamp( hDC, s_oldHardwareGamma );
	ReleaseDC( GetDesktopWindow(), hDC );

	if (!glConfig.deviceSupportsGamma)
		return;

	// do a sanity check on the gamma values
	if ( ( HIBYTE( s_oldHardwareGamma[0][255] ) <= HIBYTE( s_oldHardwareGamma[0][0] ) ) ||
		 ( HIBYTE( s_oldHardwareGamma[1][255] ) <= HIBYTE( s_oldHardwareGamma[1][0] ) ) ||
		 ( HIBYTE( s_oldHardwareGamma[2][255] ) <= HIBYTE( s_oldHardwareGamma[2][0] ) ) )
	{
		glConfig.deviceSupportsGamma = qfalse;
		ri.Printf( PRINT_WARNING, "WARNING: device has broken gamma support\n" );
	}

	// make sure that we didn't have a prior crash in the game:
	// if so, we need to restore the gamma values to at least a linear value
	if ( ( HIBYTE( s_oldHardwareGamma[0][181] ) == 255 ) )
	{
		ri.Printf( PRINT_WARNING, "WARNING: suspicious gamma tables, using linear ramp for restoration\n" );
		for (unsigned short g = 0; g < 255; ++g)
		{
			s_oldHardwareGamma[0][g] = g << 8;
			s_oldHardwareGamma[1][g] = g << 8;
			s_oldHardwareGamma[2][g] = g << 8;
		}
	}
}


void GLW_RestoreGamma()
{
	if (!glConfig.deviceSupportsGamma || !glw_state.gammaRampSet)
		return;

	HDC hDC = GetDC( GetDesktopWindow() );
	if ( SetDeviceGammaRamp( hDC, s_oldHardwareGamma ) )
		glw_state.gammaRampSet = qfalse;
	ReleaseDC( GetDesktopWindow(), hDC );
}


void GLimp_SetGamma( unsigned char red[256], unsigned char green[256], unsigned char blue[256] )
{
	unsigned short table[3][256];
	int i, j;

	if ( !glConfig.deviceSupportsGamma || r_ignorehwgamma->integer || !glw_state.hDC )
		return;

	for ( i = 0; i < 256; i++ ) {
		table[0][i] = ( ( ( unsigned short ) red[i] ) << 8 ) | red[i];
		table[1][i] = ( ( ( unsigned short ) green[i] ) << 8 ) | green[i];
		table[2][i] = ( ( ( unsigned short ) blue[i] ) << 8 ) | blue[i];
	}

	for ( j = 0 ; j < 3 ; j++ ) {
		for ( i = 0 ; i < 128 ; i++ ) {
			if ( table[j][i] > ( (128+i) << 8 ) ) {
				table[j][i] = (128+i) << 8;
			}
		}
		if ( table[j][127] > 254<<8 ) {
			table[j][127] = 254<<8;
		}
	}

	if ( SetDeviceGammaRamp( glw_state.hDC, table ) ) {
		glw_state.gammaRampSet = qtrue;
	} else {
		Com_Printf( "SetDeviceGammaRamp failed.\n" );
	}
}


///////////////////////////////////////////////////////////////


/*
This is the platform specific OpenGL initialization function.
It is responsible for loading OpenGL, initializing it, setting
extensions, creating a window of the appropriate size, doing
fullscreen manipulations, etc.  Its overall responsibility is
to make sure that a functional OpenGL subsystem is operating
when it returns to the ref.
*/
void GLimp_Init()
{
	ri.Printf( PRINT_DEVELOPER, "Initializing OpenGL subsystem\n" );

	// save off hInstance for the subsystems
	const cvar_t* cv = ri.Cvar_Get( "win_hinstance", "", 0 );
	sscanf( cv->string, "%i", (int *)&g_wv.hInstance );

	// load appropriate DLL and initialize subsystem
	if (!GLW_LoadOpenGL())
		ri.Error( ERR_FATAL, "GLimp_Init() - could not load OpenGL subsystem\n" );

	// get our config strings
	Q_strncpyz( glConfig.vendor_string, (const char*)qglGetString (GL_VENDOR), sizeof( glConfig.vendor_string ) );
	Q_strncpyz( glConfig.renderer_string, (const char*)qglGetString (GL_RENDERER), sizeof( glConfig.renderer_string ) );
	Q_strncpyz( glConfig.version_string, (const char*)qglGetString (GL_VERSION), sizeof( glConfig.version_string ) );
	Q_strncpyz( glConfig.extensions_string, (const char*)qglGetString (GL_EXTENSIONS), sizeof( glConfig.extensions_string ) );

	GLW_InitExtensions();
	GLW_CheckHardwareGamma();

	if (GLW_InitARB() && QGL_InitARB())
		return;

	ri.Error( ERR_FATAL, "GLimp_Init() - could not find an acceptable OpenGL subsystem\n" );
}


// do all OS specific shutdown procedures for the OpenGL subsystem

void GLimp_Shutdown()
{
	const char* success[] = { "failed", "success" };
	int retVal;

	// FIXME: Brian, we need better fallbacks from partially initialized failures
	if ( !qwglMakeCurrent ) {
		return;
	}

	ri.Printf( PRINT_DEVELOPER, "Shutting down OpenGL subsystem\n" );

	GLW_RestoreGamma();

	// set current context to NULL
	if ( qwglMakeCurrent )
	{
		retVal = qwglMakeCurrent( NULL, NULL ) != 0;
		ri.Printf( PRINT_DEVELOPER, "...wglMakeCurrent( NULL, NULL ): %s\n", success[retVal] );
	}

	// delete HGLRC
	if ( glw_state.hGLRC )
	{
		retVal = qwglDeleteContext( glw_state.hGLRC ) != 0;
		ri.Printf( PRINT_DEVELOPER, "...deleting GL context: %s\n", success[retVal] );
		glw_state.hGLRC = NULL;
	}

	// release DC
	if ( glw_state.hDC )
	{
		retVal = ReleaseDC( g_wv.hWnd, glw_state.hDC ) != 0;
		ri.Printf( PRINT_DEVELOPER, "...releasing DC: %s\n", success[retVal] );
		glw_state.hDC   = NULL;
	}

	// destroy window
	if ( g_wv.hWnd )
	{
		ri.Printf( PRINT_DEVELOPER, "...destroying window\n" );
		ShowWindow( g_wv.hWnd, SW_HIDE );
		DestroyWindow( g_wv.hWnd );
		g_wv.hWnd = NULL;
		glw_state.pixelFormatSet = qfalse;
	}

	// reset display settings
	if ( glw_state.cdsFullscreen )
	{
		ri.Printf( PRINT_DEVELOPER, "...resetting display\n" );
		ChangeDisplaySettings( 0, 0 );
		glw_state.cdsFullscreen = qfalse;
	}

	// shutdown QGL subsystem
	QGL_Shutdown();

	memset( &glConfig, 0, sizeof( glConfig ) );
	memset( &glState, 0, sizeof( glState ) );
}


/*
===========================================================

SMP acceleration

===========================================================
*/

static HANDLE renderCommandsEvent;
static HANDLE renderCompletedEvent;
static HANDLE renderActiveEvent;

static void (*glimpRenderThread)( void );

static void GLimp_RenderThreadWrapper()
{
	glimpRenderThread();
	// unbind the context before we die
	qwglMakeCurrent( glw_state.hDC, NULL );
}

qbool GLimp_SpawnRenderThread( void (*function)( void ) )
{
	renderCommandsEvent = CreateEvent( NULL, TRUE, FALSE, NULL );
	renderCompletedEvent = CreateEvent( NULL, TRUE, FALSE, NULL );
	renderActiveEvent = CreateEvent( NULL, TRUE, FALSE, NULL );

	glimpRenderThread = function;

	DWORD renderThreadId;
	HANDLE renderThreadHandle = CreateThread(
	   NULL,	// LPSECURITY_ATTRIBUTES lpsa,
	   0,		// DWORD cbStack,
	   (LPTHREAD_START_ROUTINE)GLimp_RenderThreadWrapper,	// LPTHREAD_START_ROUTINE lpStartAddr,
	   0,			// LPVOID lpvThreadParm,
	   0,			//   DWORD fdwCreate,
	   &renderThreadId );

	return (renderThreadHandle != NULL);
}


static	void	*smpData;
static	int		wglErrors;

void *GLimp_RendererSleep( void ) {
	void	*data;

	if ( !qwglMakeCurrent( glw_state.hDC, NULL ) ) {
		wglErrors++;
	}

	ResetEvent( renderActiveEvent );

	// after this, the front end can exit GLimp_FrontEndSleep
	SetEvent( renderCompletedEvent );

	WaitForSingleObject( renderCommandsEvent, INFINITE );

	if ( !qwglMakeCurrent( glw_state.hDC, glw_state.hGLRC ) ) {
		wglErrors++;
	}

	ResetEvent( renderCompletedEvent );
	ResetEvent( renderCommandsEvent );

	data = smpData;

	// after this, the main thread can exit GLimp_WakeRenderer
	SetEvent( renderActiveEvent );

	return data;
}


void GLimp_FrontEndSleep( void ) {
	WaitForSingleObject( renderCompletedEvent, INFINITE );

	if ( !qwglMakeCurrent( glw_state.hDC, glw_state.hGLRC ) ) {
		wglErrors++;
	}
}


void GLimp_WakeRenderer( void *data ) {
	smpData = data;

	if ( !qwglMakeCurrent( glw_state.hDC, NULL ) ) {
		wglErrors++;
	}

	// after this, the renderer can continue through GLimp_RendererSleep
	SetEvent( renderCommandsEvent );

	WaitForSingleObject( renderActiveEvent, INFINITE );
}