/**

  * $Id: gl_common.c,v 1.4 2007-10-13 04:01:02 nkeynes Exp $

  *

  * Common GL code that doesn't depend on a specific implementation

  *

  * Copyright (c) 2005 Nathan Keynes.

  *

  * This program 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.

  *

  * This program 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.

  */

 #include <sys/time.h>

 #include <GL/gl.h>

 #include "dream.h"

 #include "drivers/gl_common.h"

 extern uint32_t video_width, video_height;

 static GLuint frame_last_texid = 0, fbuf_id = 0;

 static uint32_t frame_width = 0;

 static uint32_t frame_height = 0;

 static uint32_t frame_colour = 0;

 static gboolean frame_inverted = FALSE;

 char *required_extensions[] = { "GL_EXT_framebuffer_object", NULL };

 /**

  * Test if a specific extension is supported. From opengl.org

  * @param extension extension name to check for

  * @return TRUE if supported, otherwise FALSE.

  */

 gboolean isGLExtensionSupported( const char *extension )

 {

     const GLubyte *extensions = NULL;

     const GLubyte *start;

     GLubyte *where, *terminator;

     /* Extension names should not have spaces. */

     where = (GLubyte *) strchr(extension, ' ');

     if (where || *extension == '\0')

 	return 0;

     extensions = glGetString(GL_EXTENSIONS);

     /* 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 = (GLubyte *) strstr((const char *) start, extension);

 	if (!where)

 	    break;

 	terminator = where + strlen(extension);

 	if (where == start || *(where - 1) == ' ')

 	    if (*terminator == ' ' || *terminator == '\0')

 		return TRUE;

 	start = terminator;

     }

     return FALSE;

 }

 gboolean hasRequiredGLExtensions( ) 

 {

     int i;

     gboolean isOK = TRUE;

     for( i=0; required_extensions[i] != NULL; i++ ) {

 	if( !isGLExtensionSupported(required_extensions[i]) ) {

 	    ERROR( "Required OpenGL extension not supported: %s", required_extensions[i] );

 	    isOK = FALSE;

 	}

     }

     return isOK;

 }

 void gl_frame_buffer_to_tex_rectangle( frame_buffer_t frame, GLuint texid )

 {

     GLenum type = colour_formats[frame->colour_format].type;

     GLenum format = colour_formats[frame->colour_format].format;

     int bpp = colour_formats[frame->colour_format].bpp;

     int rowstride = (frame->rowstride / bpp) - frame->width;

     glPixelStorei( GL_UNPACK_ROW_LENGTH, rowstride );

     glBindTexture( GL_TEXTURE_RECTANGLE_ARB, texid );

     glTexImage2D( GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGB,

 		  frame->width, frame->height, 0, format, type, frame->data );

 }

 void gl_display_tex_rectangle( GLuint texid, uint32_t tex_width, uint32_t tex_height, gboolean invert )

 {

     float top, bottom;

     if( invert ) {

 	top = ((float)tex_height) - 0.5;

 	bottom = 0.5;

     } else {

 	top = 0.5;

 	bottom = ((float)tex_height) - 0.5;

     }

     /* Reset display parameters */

     glViewport( 0, 0, video_width, video_height );

     glMatrixMode(GL_PROJECTION);

     glLoadIdentity();

     glOrtho( 0, video_width, video_height, 0, 0, -65535 );

     glMatrixMode(GL_MODELVIEW);

     glLoadIdentity();

     glDisable( GL_TEXTURE_2D );

     glDisable( GL_ALPHA_TEST );

     glDisable( GL_DEPTH_TEST );

     glDisable( GL_SCISSOR_TEST );

     glDisable( GL_CULL_FACE );

     /* Render the textured rectangle */

     glEnable( GL_TEXTURE_RECTANGLE_ARB );

     glBindTexture( GL_TEXTURE_RECTANGLE_ARB, texid );

     glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE );

     glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

     glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

     glEnable( GL_BLEND );

     glBlendFunc( GL_ONE, GL_ZERO );

     glBegin( GL_QUADS );

     glTexCoord2f( 0.5, top );

     glVertex2f( 0.0, 0.0 );

     glTexCoord2f( ((float)tex_width)-0.5, top );

     glVertex2f( video_width, 0.0 );

     glTexCoord2f( ((float)tex_width)-0.5, bottom );

     glVertex2f( video_width, video_height );

     glTexCoord2f( 0.5, bottom );

     glVertex2f( 0.0, video_height );

     glEnd();

     glDisable( GL_TEXTURE_RECTANGLE_ARB );

     glFlush();

     frame_last_texid = texid;

     frame_width = tex_width;

     frame_height = tex_height;

     frame_inverted = invert;

 }

 gboolean gl_display_frame_buffer( frame_buffer_t frame )

 {

     if( fbuf_id == 0 ) {

 	glGenTextures( 1, &fbuf_id );

     }

     gl_frame_buffer_to_tex_rectangle( frame, fbuf_id );

     gl_display_tex_rectangle( fbuf_id, frame->width, frame->height, FALSE );

     return TRUE;

 }

 gboolean gl_display_blank( uint32_t colour )

 {

     glViewport( 0, 0, video_width, video_height );

     glMatrixMode( GL_PROJECTION );

     glLoadIdentity();

     glOrtho( 0, video_width, video_height, 0, 0, -65535 );

     glMatrixMode(GL_MODELVIEW);

     glLoadIdentity();

     glColor3b( (colour >> 16) & 0xFF, (colour >> 8) & 0xFF, colour & 0xFF );

     glRecti(0,0, video_width, video_height );

     glFlush();

     frame_colour = colour;

     frame_last_texid = 0;

     return TRUE;

 }

 void gl_redisplay_last()

 {

     if( frame_last_texid == 0 ) {

 	gl_display_blank( frame_colour );

     } else {

 	gl_display_tex_rectangle( frame_last_texid, frame_width, frame_height, frame_inverted );

     }

 }

 /**

  * Generic GL read_render_buffer. This function assumes that the caller

  * has already set the appropriate glReadBuffer(); in other words, unless

  * there's only one buffer this needs to be wrapped.

  */

 gboolean gl_read_render_buffer( render_buffer_t buffer, unsigned char *target ) 

 {

     if( buffer->address == -1 )

 	return FALSE;

     glFinish();

     GLenum type = colour_formats[buffer->colour_format].type;

     GLenum format = colour_formats[buffer->colour_format].format;

     // int line_size = buffer->width * colour_formats[buffer->colour_format].bpp;

     // int size = line_size * buffer->height;

     // int rowstride = (buffer->rowstride / colour_formats[buffer->colour_format].bpp) - buffer->width;

     // glPixelStorei( GL_PACK_ROW_LENGTH, rowstride );

     glReadPixels( 0, 0, buffer->width, buffer->height, format, type, target );

     return TRUE;

 }