/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997, 1998, 1999, 2000, 2001  Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 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
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    slouken@libsdl.org
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id$";
#endif

/* WGL implementation of SDL OpenGL support */

#include <windows.h>

#include "SDL_error.h"
#include "SDL_lowvideo.h"
#include "SDL_wingl_c.h"

#ifdef HAVE_OPENGL
#define DEFAULT_GL_DRIVER_PATH "OPENGL32.DLL"
#endif


int WIN_GL_SetupWindow(_THIS)
{
	int retval;
#ifdef HAVE_OPENGL
	int pixel_format;

	/* 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);
		}
	}

	/* 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);
	}

	/* Set up the pixel format descriptor with our needed format */
	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;
	}
	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;

	/* Choose and set the closest available 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) ) {
		SDL_SetError("Unable to set HDC pixel format");
		return(-1);
	}
	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);
	}
	gl_active = 1;
#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)
{
#ifdef HAVE_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 /* HAVE_OPENGL */
}

#ifdef HAVE_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 glX. */
int WIN_GL_GetAttribute(_THIS, SDL_GLattr attrib, int* value)
{
	int retval;

	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;
	    default:
		retval = -1;
		break;
	}
	return retval;
}

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

#endif /* HAVE_OPENGL */

#ifdef HAVE_OPENGL

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_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 */
	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");

	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;
	strcpy(this->gl_config.driver_path, 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 /* HAVE_OPENGL */