/**

 * $Id: gl_fbo.c,v 1.1 2007-02-11 10:09:32 nkeynes Exp $

 *

 * GL framebuffer-based driver shell. This requires the EXT_framebuffer_object

 * extension, but is much nicer/faster/etc than pbuffers when it's available.

 * This is (optionally) used indirectly by the top-level GLX driver.

 *

 * Strategy-wise, we maintain 2 framebuffers with up to 4 target colour

 * buffers a piece. Effectively this reserves one fb for display output,

 * and the other for texture output (each fb has a single size).

 *

 * 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 <GL/gl.h>

#include "display.h"

#define MAX_FRAMEBUFFERS 2

#define MAX_TEXTURES_PER_FB 4

static render_buffer_t gl_fbo_create_render_buffer( uint32_t width, uint32_t height );

static void gl_fbo_destroy_render_buffer( render_buffer_t buffer );

static gboolean gl_fbo_set_render_target( render_buffer_t buffer );

static gboolean gl_fbo_display_render_buffer( render_buffer_t buffer );

static gboolean gl_fbo_display_frame_buffer( frame_buffer_t buffer );

static gboolean gl_fbo_display_blank( uint32_t colour );

static gboolean gl_fbo_read_render_buffer( render_buffer_t buffer, char *target );

extern uint32_t video_width, video_height;

/**

 * Framebuffer info structure

 */

struct gl_fbo_info {

    GLuint fb_id;

    GLuint depth_id;

    GLuint stencil_id;

    GLuint tex_ids[MAX_TEXTURES_PER_FB];

    int width, height;

};

static struct gl_fbo_info fbo[MAX_FRAMEBUFFERS];

const static int ATTACHMENT_POINTS[MAX_TEXTURES_PER_FB] = {

    GL_COLOR_ATTACHMENT0_EXT, GL_COLOR_ATTACHMENT1_EXT, 

    GL_COLOR_ATTACHMENT2_EXT, GL_COLOR_ATTACHMENT3_EXT };

static int last_used_fbo;

gboolean gl_fbo_is_supported()

{

    return isGLExtensionSupported("GL_EXT_framebuffer_object");

}

/**

 * Construct the initial frame buffers and allocate ids for everything.

 * The render handling driver methods are set to the fbo versions.

 */

void gl_fbo_init( display_driver_t driver ) 

{

    int i,j;

    int fbids[MAX_FRAMEBUFFERS];

    int rbids[MAX_FRAMEBUFFERS*2]; /* depth buffer, stencil buffer per fb */

    glGenFramebuffersEXT( MAX_FRAMEBUFFERS, &fbids );

    glGenRenderbuffersEXT( MAX_FRAMEBUFFERS*2, &rbids );

    for( i=0; i<MAX_FRAMEBUFFERS; i++ ) {

	fbo[i].fb_id = fbids[i];

	fbo[i].depth_id = rbids[i*2];

	fbo[i].stencil_id = rbids[i*2+1];

	fbo[i].width = -1;

	fbo[i].height = -1;

	for( j=0; j<MAX_TEXTURES_PER_FB; j++ ) {

	    fbo[i].tex_ids[j] = -1;

	}

    }

    last_used_fbo = 0;

    driver->create_render_buffer = gl_fbo_create_render_buffer;

    driver->destroy_render_buffer = gl_fbo_destroy_render_buffer;

    driver->set_render_target = gl_fbo_set_render_target;

    driver->display_render_buffer = gl_fbo_display_render_buffer;

    driver->display_frame_buffer = gl_fbo_display_frame_buffer;

    driver->display_blank = gl_fbo_display_blank;

    driver->read_render_buffer = gl_fbo_read_render_buffer;

}

void gl_fbo_shutdown()

{

    int i;

    glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, 0 );

    for( i=0; i<MAX_FRAMEBUFFERS; i++ ) {

	glDeleteFramebuffersEXT( 1, &fbo[i].fb_id );

	glDeleteRenderbuffersEXT( 2, &fbo[i].depth_id );

    }

}

void gl_fbo_setup_framebuffer( int bufno, int width, int height )

{

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo[bufno].fb_id);

    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, fbo[bufno].depth_id);

    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, width, height);

    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,

				 GL_RENDERBUFFER_EXT, fbo[bufno].depth_id);

    /* Stencil doesn't work on ATI, and we're not using it at the moment anyway, so...

    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, fbo[bufno].stencil_id);

    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_STENCIL_INDEX, width, height);

    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_STENCIL_ATTACHMENT_EXT,

				 GL_RENDERBUFFER_EXT, fbo[bufno].stencil_id);

    */

    fbo[bufno].width = width;

    fbo[bufno].height = height;

}

int gl_fbo_get_framebuffer( int width, int height ) 

{

    int bufno = -1, i;

    /* find a compatible framebuffer context */

    for( i=0; i<MAX_FRAMEBUFFERS; i++ ) {

	if( fbo[i].width == -1 && bufno == -1 ) {

	    bufno = i;

	} else if( fbo[i].width == width && fbo[i].height == height ) {

	    bufno = i;

	    break;

	}

    }

    if( bufno == -1 ) {

	bufno = last_used_fbo + 1;

	if( bufno > MAX_FRAMEBUFFERS ) {

	    bufno = 0;

	}

	last_used_fbo = bufno;

    }

    if( fbo[bufno].width == width && fbo[bufno].height == height ) {

	glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, fbo[bufno].fb_id );

    } else {

	gl_fbo_setup_framebuffer( bufno, width, height );

    } 

    return bufno;

}

/**

 * Attach a texture to the framebuffer. The texture must already be initialized

 * to the correct dimensions etc.

 */

static GLint gl_fbo_attach_texture( int fbo_no, GLint tex_id ) {

    int attach = -1, i;

    for( i=0; i<MAX_TEXTURES_PER_FB; i++ ) {

	if( fbo[fbo_no].tex_ids[i] == tex_id ) {

	    glDrawBuffer(ATTACHMENT_POINTS[i]);

	    glReadBuffer(ATTACHMENT_POINTS[i]); 

	    return ATTACHMENT_POINTS[i]; // already attached

	} else if( fbo[fbo_no].tex_ids[i] == -1 && attach == -1 ) {

	    attach = i;

	}

    }

    if( attach == -1 ) {

	/* should never happen */

	attach = 0;

    }

    fbo[fbo_no].tex_ids[attach] = tex_id;

    glBindTexture( GL_TEXTURE_RECTANGLE_ARB, 0 ); // Ensure the output texture is unbound

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, ATTACHMENT_POINTS[attach], 

			      GL_TEXTURE_RECTANGLE_ARB, tex_id, 0 );

    /* Set draw/read buffers by default */

    glDrawBuffer(ATTACHMENT_POINTS[attach]);

    glReadBuffer(ATTACHMENT_POINTS[attach]); 

    GLint status = glGetError();

    if( status != GL_NO_ERROR ) {

	ERROR( "GL error setting render target (%x)!", status );

    }

    status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);

    if( status != GL_FRAMEBUFFER_COMPLETE_EXT ) {

	ERROR( "Framebuffer failure: %x", status );

	exit(1);

    }

    return ATTACHMENT_POINTS[attach];

}

static render_buffer_t gl_fbo_create_render_buffer( uint32_t width, uint32_t height )

{

    render_buffer_t buffer = calloc( sizeof(struct render_buffer), 1 );

    buffer->width = width;

    buffer->height = height;

    glGenTextures( 1, &buffer->buf_id );

    glBindTexture( GL_TEXTURE_RECTANGLE_ARB, buffer->buf_id );

    glTexParameteri( GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_S, GL_CLAMP );

    glTexParameteri( GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_T, GL_CLAMP );

    glTexParameteri( GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_NEAREST );

    glTexParameteri( GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST );

    glTexImage2D( GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL );

    return buffer;

}

static void gl_fbo_destroy_render_buffer( render_buffer_t buffer )

{

    int i,j;

    for( i=0; i<MAX_FRAMEBUFFERS; i++ ) {

	for( j=0; j < MAX_TEXTURES_PER_FB; j++ ) {

	    if( fbo[i].tex_ids[j] == buffer->buf_id ) {

		glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, ATTACHMENT_POINTS[j], 

					  GL_TEXTURE_RECTANGLE_ARB, GL_NONE, 0 );

		fbo[i].tex_ids[j] = -1;

	    }

	}

    }

    glDeleteTextures( 1, &buffer->buf_id );

    buffer->buf_id = 0;

    free( buffer );

}

static gboolean gl_fbo_set_render_target( render_buffer_t buffer )

{

    glGetError();

    int fb = gl_fbo_get_framebuffer( buffer->width, buffer->height );

    GLint attach = gl_fbo_attach_texture( fb, buffer->buf_id );

    /* setup the gl context */

    glViewport( 0, 0, buffer->width, buffer->height );

    return TRUE;

}

/**

 * Render the texture holding the given buffer to the front window

 * buffer.

 */

static gboolean gl_fbo_display_render_buffer( render_buffer_t buffer )

{

    glFinish();

    glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, 0 ); // real window

    glViewport( 0, 0, video_width, video_height );

    glEnable( GL_TEXTURE_RECTANGLE_ARB );

    glBindTexture( GL_TEXTURE_RECTANGLE_ARB, buffer->buf_id );

    glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE );

    glDrawBuffer( GL_FRONT );

    glReadBuffer( GL_FRONT );

    glDisable( GL_ALPHA_TEST );

    glDisable( GL_DEPTH_TEST );

    glDisable( GL_SCISSOR_TEST );

    glDisable( GL_CULL_FACE );

    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();

    glOrtho( 0, buffer->width, buffer->height, 0, 0, -65535 );

    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();

    glEnable( GL_BLEND );

    glBlendFunc( GL_ONE, GL_ZERO );

    glDisable( GL_DEPTH_TEST );

    glBegin( GL_QUADS );

    glTexCoord2i( 0, buffer->height );

    glVertex2f( 0.0, 0.0 );

    glTexCoord2i( buffer->width, buffer->height );

    glVertex2f( buffer->width, 0.0 );

    glTexCoord2i( buffer->width, 0 );

    glVertex2f( buffer->width, buffer->height );

    glTexCoord2i( 0, 0 );

    glVertex2f( 0.0, buffer->height );

    glEnd();

    glDisable( GL_TEXTURE_RECTANGLE_ARB );

    glFlush();

    return TRUE;

}

static gboolean gl_fbo_display_frame_buffer( frame_buffer_t buffer )

{

    glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, 0 );

    glDrawBuffer( GL_FRONT );

    glReadBuffer( GL_FRONT );

    return gl_display_frame_buffer( buffer );

}

static gboolean gl_fbo_display_blank( uint32_t colour )

{

    glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, 0 );

    glDrawBuffer( GL_FRONT );

    glReadBuffer( GL_FRONT );

    return gl_display_blank( colour );

}

static gboolean gl_fbo_read_render_buffer( render_buffer_t buffer, char *target )

{

    int fb = gl_fbo_get_framebuffer( buffer->width, buffer->height );

    GLint attach = gl_fbo_attach_texture( fb, buffer->buf_id );

    return gl_read_render_buffer( buffer, target );

}