/**

  * $Id$

  *

  * 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/video_gl.h"

 #include "pvr2/glutil.h"

 #if defined(HAVE_OPENGL_FBO) || defined(HAVE_OPENGL_FBO_EXT)

 #define MAX_FRAMEBUFFERS 2

 #define MAX_TEXTURES_PER_FB 16

 static render_buffer_t gl_fbo_create_render_buffer( uint32_t width, uint32_t height, GLuint tex_id );

 static void gl_fbo_destroy_render_buffer( render_buffer_t buffer );

 static gboolean gl_fbo_set_render_target( render_buffer_t buffer );

 static void gl_fbo_finish_render( render_buffer_t buffer );

 static void 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 void gl_fbo_display_blank( uint32_t colour );

 static gboolean gl_fbo_test_framebuffer( );

 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 GLint gl_fbo_max_attachments = 0;

 static gboolean gl_fbo_have_packed_stencil = FALSE;

 static struct gl_fbo_info fbo[MAX_FRAMEBUFFERS];

 #define ATTACHMENT_POINT(n) (GL_COLOR_ATTACHMENT0+(n))

 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 */

     gl_fbo_max_attachments = glGetMaxColourAttachments();

     glGenFramebuffers( MAX_FRAMEBUFFERS, &fbids[0] );

     glGenRenderbuffers( 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;

     if( isGLExtensionSupported("GL_EXT_packed_depth_stencil" ) ) {

         driver->capabilities.stencil_bits = 8;

         gl_fbo_have_packed_stencil = TRUE;

     } else {

         driver->capabilities.stencil_bits = 0;

         gl_fbo_have_packed_stencil = FALSE;

         WARN( "Packed depth stencil not available - disabling shadow volumes" );

     }

     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->finish_render = gl_fbo_finish_render;

     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;

     gl_fbo_test_framebuffer();

     glBindFramebuffer(GL_FRAMEBUFFER, 0);

 }

 void gl_fbo_shutdown()

 {

     int i;

     glBindFramebuffer( GL_FRAMEBUFFER, 0 );

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

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

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

     }

 }

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

 {

     int i;

     glBindFramebuffer(GL_FRAMEBUFFER, fbo[bufno].fb_id);

     /* Clear out any existing texture attachments */

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

         if( fbo[bufno].tex_ids[i] != -1 ) {

             glFramebufferTexture2D(GL_FRAMEBUFFER, ATTACHMENT_POINT(i),

                     GL_TEXTURE_2D, 0, 0);

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

         }

     }

     /* Setup the renderbuffers */

     if( gl_fbo_have_packed_stencil ) {

         glBindRenderbuffer(GL_RENDERBUFFER, fbo[bufno].depth_id);

         glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, width, height);

         glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,

                                      GL_RENDERBUFFER, fbo[bufno].depth_id);

         glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT,

                                      GL_RENDERBUFFER, fbo[bufno].depth_id);

     } else {

         glBindRenderbuffer(GL_RENDERBUFFER, fbo[bufno].depth_id);

         glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, width, height);

         glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,

                                      GL_RENDERBUFFER, fbo[bufno].depth_id);

         /* In theory you could attach a separate stencil buffer. In practice this 

          * isn't actually supported by any hardware I've had access to, so we're

          * stencil-less.

          */

     }

     fbo[bufno].width = width;

     fbo[bufno].height = height;

 }

 static 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 ) {

         glBindFramebuffer( GL_FRAMEBUFFER, 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<gl_fbo_max_attachments; i++ ) {

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

 #ifdef HAVE_OPENGL_DRAW_BUFFER

             glDrawBuffer(ATTACHMENT_POINT(i));

             glReadBuffer(ATTACHMENT_POINT(i)); 

 #endif

             return ATTACHMENT_POINT(i); // already attached

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

             attach = i;

         }

     }

     if( attach == -1 ) {

         attach = 0;

     }

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

     glBindTexture( GL_TEXTURE_2D, 0 ); // Ensure the output texture is unbound

     glFramebufferTexture2D(GL_FRAMEBUFFER, ATTACHMENT_POINT(attach), 

                               GL_TEXTURE_2D, tex_id, 0 );

     /* Set draw/read buffers by default */

 #ifdef HAVE_OPENGL_DRAW_BUFFER    

     glDrawBuffer(ATTACHMENT_POINT(attach));

     glReadBuffer(ATTACHMENT_POINT(attach)); 

 #endif

     return ATTACHMENT_POINT(attach);

 }

 static gboolean gl_fbo_test_framebuffer( )

 {

     gboolean result = TRUE;

     glGetError(); /* Clear error state just in case */

     render_buffer_t buffer = gl_fbo_create_render_buffer( 640, 480, 0 );

     gl_fbo_set_render_target(buffer);

     GLint status = glCheckFramebufferStatus(GL_FRAMEBUFFER);

     if( status != GL_FRAMEBUFFER_COMPLETE ) {

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

         result = FALSE;

     }

     if( result ) {

         result = gl_check_error( "Setting up framebuffer" );

     }

     gl_fbo_destroy_render_buffer( buffer );

     return result;

 }

 static render_buffer_t gl_fbo_create_render_buffer( uint32_t width, uint32_t height, GLuint tex_id )

 {

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

     buffer->width = width;

     buffer->height = height;

     buffer->tex_id = tex_id;

     if( tex_id == 0 ) {

         GLuint tex;

         glGenTextures( 1, &tex );

         buffer->buf_id = tex;

     } else {

         buffer->buf_id = tex_id;

         glBindTexture( GL_TEXTURE_2D, tex_id );

     }

     glBindTexture( GL_TEXTURE_2D, buffer->buf_id );

     glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL );

     glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );

     glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );

     glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );

     glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );

     return buffer;

 }

 /**

  * Ensure the texture in the given render buffer is not attached to a 

  * framebuffer (ie, so we can safely use it as a texture during the rendering

  * cycle, or before deletion).

  */

 static void gl_fbo_detach_render_buffer( render_buffer_t buffer )

 {

     int i,j;

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

         if( fbo[i].width == buffer->width && fbo[i].height == buffer->height ) {

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

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

                     glBindFramebuffer(GL_FRAMEBUFFER, fbo[i].fb_id);

                     glFramebufferTexture2D(GL_FRAMEBUFFER, ATTACHMENT_POINT(j), 

                                               GL_TEXTURE_2D, GL_NONE, 0 );

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

                     return;

                 }                    

             }

             break;

         }

     }

 }

 static void gl_fbo_destroy_render_buffer( render_buffer_t buffer )

 {

     int i,j;

     gl_fbo_detach_render_buffer( buffer );

     if( buffer->buf_id != buffer->tex_id ) {

         // If tex_id was set at buffer creation, we don't own the texture.

         // Otherwise, delete it now.

         GLuint tex = buffer->buf_id; 

         glDeleteTextures( 1, &tex );

     }

     buffer->buf_id = 0;

     buffer->tex_id = 0;

     free( buffer );

 }

 static gboolean gl_fbo_set_render_target( render_buffer_t buffer )

 {

     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;

 }

 static void gl_fbo_finish_render( render_buffer_t buffer )

 {

     glFinish();

     gl_fbo_detach_render_buffer(buffer);

 }

 /**

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

  * buffer.

  */

 static void gl_fbo_display_render_buffer( render_buffer_t buffer )

 {

     gl_fbo_detach();

     gl_display_render_buffer( buffer );

 }

 static void gl_fbo_load_frame_buffer( frame_buffer_t frame, render_buffer_t buffer )

 {

     gl_fbo_detach();

     gl_load_frame_buffer( frame, buffer->buf_id );

 }

 static void gl_fbo_display_blank( uint32_t colour )

 {

     gl_fbo_detach();

     gl_display_blank( colour );

 }

 void gl_fbo_detach()

 {

     glBindFramebuffer( GL_FRAMEBUFFER, 0 );

     /* Make sure texture attachment is not a current draw/read buffer */

 #ifdef HAVE_OPENGL_DRAW_BUFFER

     glDrawBuffer( GL_FRONT );

     glReadBuffer( GL_FRONT );

 #endif

     display_driver->swap_buffers();

 }    

 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 );

 }

 #else

 gboolean gl_fbo_is_supported()

 {

     return FALSE;

 }

 void gl_fbo_init( display_driver_t driver ) 

 {

 }

 #endif