/**

  * $Id: gl_fbo.c,v 1.7 2007-10-31 09:10:23 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.

  */

 #define GL_GLEXT_PROTOTYPES 1

 #include <stdlib.h>

 #include "lxdream.h"

 #include "display.h"

 #include "drivers/gl_common.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 void gl_fbo_load_frame_buffer( frame_buffer_t frame, render_buffer_t buffer );

 static gboolean gl_fbo_display_blank( uint32_t colour );

 static gboolean gl_fbo_read_render_buffer( unsigned char *target, render_buffer_t buffer, int rowstride, int format );

 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;

     GLuint fbids[MAX_FRAMEBUFFERS];

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

     glGenFramebuffersEXT( MAX_FRAMEBUFFERS, &fbids[0] );

     glGenRenderbuffersEXT( MAX_FRAMEBUFFERS*2, &rbids[0] );

     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->load_frame_buffer = gl_fbo_load_frame_buffer;

     driver->display_blank = gl_fbo_display_blank;

     driver->read_render_buffer = gl_fbo_read_render_buffer;

     glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

     glDrawBuffer(GL_FRONT);

     glReadBuffer(GL_FRONT);

 }

 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 ) {

 		glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo[i].fb_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 )

 {

     glFinish();

     glGetError();

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

     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();

     gl_fbo_detach();

     gl_display_render_buffer( buffer );

     return TRUE;

 }

 static void gl_fbo_load_frame_buffer( frame_buffer_t frame, render_buffer_t buffer )

 {

     glFinish();

     gl_fbo_detach();

     gl_load_frame_buffer( frame, buffer->buf_id );

 }

 static gboolean gl_fbo_display_blank( uint32_t colour )

 {

     glFinish();

     gl_fbo_detach();

     return gl_display_blank( colour );

 }

 void gl_fbo_detach()

 {

     glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, 0 );

     glDrawBuffer( GL_FRONT );

     glReadBuffer( GL_FRONT );

 }    

 static gboolean gl_fbo_read_render_buffer( unsigned char *target, render_buffer_t buffer, 

 					   int rowstride, int format )

 {

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

     gl_fbo_attach_texture( fb, buffer->buf_id );

     return gl_read_render_buffer( target, buffer, rowstride, format );

 }