/**

 * $Id$

 *

 * 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") || isOpenGLES2();

}

/**

 * 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

    if( display_driver->swap_buffers )

        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