/**

 * $Id: gl_common.c,v 1.5 2007-10-14 09:30:16 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 );

    glColor3f( 0,0,0 );

    int x1=0,y1=0,x2=video_width,y2=video_height;

    int ah = video_width * 0.75;

    if( ah > video_height ) {

	int w = (video_height/0.75);

	x1 = (video_width - w)/2;

	x2 -= x1;

	glBegin( GL_QUADS );

	glVertex2f( 0, 0 );

	glVertex2f( x1, 0 );

	glVertex2f( x1, video_height );

	glVertex2f( 0, video_height);

	glVertex2f( x2, 0 );

	glVertex2f( video_width, 0 );

	glVertex2f( video_width, video_height );

	glVertex2f( x2, video_height);

	glEnd();

    } else if( ah < video_height ) {

	y1 = (video_height - ah)/2;

	y2 -= y1;

	glBegin( GL_QUADS );

	glVertex2f( 0, 0 );

	glVertex2f( video_width, 0 );

	glVertex2f( video_width, y1 );

	glVertex2f( 0, y1 );

	glVertex2f( 0, y2 );

	glVertex2f( video_width, y2 );

	glVertex2f( video_width, video_height );

	glVertex2f( 0, video_height );

	glEnd();

    }

    /* 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( x1, y1 );

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

    glVertex2f( x2, y1 );

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

    glVertex2f( x2, y2 );

    glTexCoord2f( 0.5, bottom );

    glVertex2f( x1, y2 );

    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;

}