]> Pileus Git - ~andy/gtk/blobdiff - gdk-pixbuf/io-gif.c
Add icc-profile option to gdk-pixbuf for the TIFF image format
[~andy/gtk] / gdk-pixbuf / io-gif.c
index cd2221a1b87873221dc97a622d4552df7836d43e..d414d782013def3a6dd29ed42c26ef88fd8af66d 100644 (file)
@@ -1,3 +1,4 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*- */
 /* GdkPixbuf library - GIF image loader
  *
  * Copyright (C) 1999 Mark Crichton
@@ -5,64 +6,91 @@
  *
  * Authors: Jonathan Blandford <jrb@redhat.com>
  *          Adapted from the gimp gif filter written by Adam Moss <adam@gimp.org>
- *          Gimp work based on earlier work by ......
+ *          Gimp work based on earlier work.
  *          Permission to relicense under the LGPL obtained.
  *
  * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Library General Public
+ * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library 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
- * Library General Public License for more details.
+ * Lesser General Public License for more details.
  *
- * You should have received a copy of the GNU Library General Public
+ * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the
  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 02111-1307, USA.
  */
 
-#include <config.h>
+/* This loader is very hairy code.
+ *
+ * The main loop was not designed for incremental loading, so when it was hacked
+ * in it got a bit messy.  Basicly, every function is written to expect a failed
+ * read_gif, and lets you call it again assuming that the bytes are there.
+ *
+ * Return vals.
+ * Unless otherwise specified, these are the return vals for most functions:
+ *
+ *  0 -> success
+ * -1 -> more bytes needed.
+ * -2 -> failure; abort the load
+ * -3 -> control needs to be passed back to the main loop
+ *        \_ (most of the time returning 0 will get this, but not always)
+ *
+ * >1 -> for functions that get a guchar, the char will be returned.
+ *
+ * -jrb (11/03/1999)
+ */
+
+/*
+ * If you have any images that crash this code, please, please let me know and
+ * send them to me.
+ *                                            <jrb@redhat.com>
+ */
+
+\f
+
+#include "config.h"
 #include <stdio.h>
-#include <glib.h>
 #include <string.h>
-#include "gdk-pixbuf.h"
+#include <errno.h>
+#include "gdk-pixbuf-private.h"
 #include "gdk-pixbuf-io.h"
+#include "io-gif-animation.h"
+
 \f
 
+#undef DUMP_IMAGE_DETAILS 
+#undef IO_GIFDEBUG
 
 #define MAXCOLORMAPSIZE  256
-
-#define CM_RED           0
-#define CM_GREEN         1
-#define CM_BLUE          2
-
-#define MAX_LWZ_BITS     12
+#define MAX_LZW_BITS     12
 
 #define INTERLACE          0x40
 #define LOCALCOLORMAP      0x80
 #define BitSet(byte, bit)  (((byte) & (bit)) == (bit))
 #define LM_to_uint(a,b)         (((b)<<8)|(a))
 
-#define GRAYSCALE        1
-#define COLOR            2
+\f
 
 typedef unsigned char CMap[3][MAXCOLORMAPSIZE];
 
 /* Possible states we can be in. */
 enum {
-       GIF_START = 1,
+       GIF_START,
        GIF_GET_COLORMAP,
        GIF_GET_NEXT_STEP,
        GIF_GET_FRAME_INFO,
-       GIF_GET_EXTENTION,
+       GIF_GET_EXTENSION,
        GIF_GET_COLORMAP2,
        GIF_PREPARE_LZW,
        GIF_LZW_FILL_BUFFER,
+       GIF_LZW_CLEAR_CODE,
        GIF_GET_LZW,
-       GIF_DONE,
+       GIF_DONE
 };
 
 
@@ -81,87 +109,120 @@ struct _GifContext
        int state; /* really only relevant for progressive loading */
        unsigned int width;
        unsigned int height;
-       CMap color_map;
-       unsigned int bit_pixel;
-       unsigned int color_resolution;
-       unsigned int background;
+
+        gboolean has_global_cmap;
+
+        CMap global_color_map;
+        gint global_colormap_size;
+        unsigned int global_bit_pixel;
+       unsigned int global_color_resolution;
+        unsigned int background_index;
+        gboolean stop_after_first_frame;
+
+        gboolean frame_cmap_active;
+        CMap frame_color_map;
+        gint frame_colormap_size;
+        unsigned int frame_bit_pixel;
+
        unsigned int aspect_ratio;
-       int gray_scale;
-       GdkPixbuf *pixbuf;
+       GdkPixbufGifAnim *animation;
+       GdkPixbufFrame *frame;
        Gif89 gif89;
 
-       /* stuff per frame.  As we only support the first one, not so
-        * relevant.  But still needed */
+       /* stuff per frame. */
        int frame_len;
        int frame_height;
        int frame_interlace;
+       int x_offset;
+       int y_offset;
 
        /* Static read only */
        FILE *file;
 
        /* progressive read, only. */
-       ModulePreparedNotifyFunc func;
+       GdkPixbufModulePreparedFunc prepare_func;
+       GdkPixbufModuleUpdatedFunc update_func;
        gpointer user_data;
-       guchar *buf;
+        guchar *buf;
        guint ptr;
        guint size;
        guint amount_needed;
 
-       /* colormap context */
-       gint colormap_index;
-       gint colormap_flag;
-
        /* extension context */
        guchar extension_label;
        guchar extension_flag;
+        gboolean in_loop_extension;
 
        /* get block context */
        guchar block_count;
        guchar block_buf[280];
        gint block_ptr;
 
+       int old_state; /* used by lzw_fill buffer */
        /* get_code context */
        int code_curbit;
        int code_lastbit;
        int code_done;
        int code_last_byte;
-       
-       /* lwz context */
-       gint lwz_fresh;
-       gint lwz_code_size;
-       guchar lwz_set_code_size;
-       gint lwz_max_code;
-       gint lwz_max_code_size;
-       gint lwz_firstcode;
-       gint lwz_oldcode;
-       gint lwz_clear_code;
-       gint lwz_end_code;
-       gint lwz_table[2][(1 << MAX_LWZ_BITS)];
-       gint lwz_stack[(1 << (MAX_LWZ_BITS)) * 2];
-       gint *lwz_sp;
+       int lzw_code_pending;
+
+       /* lzw context */
+       gint lzw_fresh;
+       gint lzw_code_size;
+       guchar lzw_set_code_size;
+       gint lzw_max_code;
+       gint lzw_max_code_size;
+       gint lzw_firstcode;
+       gint lzw_oldcode;
+       gint lzw_clear_code;
+       gint lzw_end_code;
+       gint *lzw_sp;
+
+       gint lzw_table[2][(1 << MAX_LZW_BITS)];
+       gint lzw_stack[(1 << (MAX_LZW_BITS)) * 2 + 1];
 
        /* painting context */
        gint draw_xpos;
        gint draw_ypos;
        gint draw_pass;
+
+        /* error pointer */
+        GError **error;
 };
 
 static int GetDataBlock (GifContext *, unsigned char *);
-static int GetCode (GifContext *, int);
 
-/* Returns TRUE if Read is OK,
- * FALSE if more memory is needed. */
+\f
+
+#ifdef IO_GIFDEBUG
 static int count = 0;
-static int
-ReadOK (GifContext *context, guchar *buffer, size_t len)
+#endif
+
+/* Returns TRUE if read is OK,
+ * FALSE if more memory is needed. */
+static gboolean
+gif_read (GifContext *context, guchar *buffer, size_t len)
 {
-       gint retval, i;
+       gboolean retval;
+#ifdef IO_GIFDEBUG
+       gint i;
+#endif
        if (context->file) {
-               count += len;
 #ifdef IO_GIFDEBUG
+               count += len;
                g_print ("Fsize :%d\tcount :%d\t", len, count);
 #endif
                retval = (fread(buffer, len, 1, context->file) != 0);
+
+                if (!retval && ferror (context->file)) {
+                        gint save_errno = errno;
+                        g_set_error (context->error,
+                                     G_FILE_ERROR,
+                                     g_file_error_from_errno (save_errno),
+                                     _("Failure reading GIF: %s"), 
+                                     g_strerror (save_errno));
+                }
+                
 #ifdef IO_GIFDEBUG
                if (len < 100) {
                        for (i = 0; i < len; i++)
@@ -169,13 +230,16 @@ ReadOK (GifContext *context, guchar *buffer, size_t len)
                }
                g_print ("\n");
 #endif
+                
                return retval;
        } else {
 #ifdef IO_GIFDEBUG
-               g_print ("\tlooking for %d bytes.  size == %d, ptr == %d\n", len, context->size, context->ptr);
+/*             g_print ("\tlooking for %d bytes.  size == %d, ptr == %d\n", len, context->size, context->ptr); */
 #endif
                if ((context->size - context->ptr) >= len) {
+#ifdef IO_GIFDEBUG
                        count += len;
+#endif
                        memcpy (buffer, context->buf + context->ptr, len);
                        context->ptr += len;
                        context->amount_needed = 0;
@@ -191,37 +255,21 @@ ReadOK (GifContext *context, guchar *buffer, size_t len)
                }
                context->amount_needed = len - (context->size - context->ptr);
        }
-       return 0;
+       return FALSE;
 }
 
-
-/*
- * Return vals.
- * Unless otherwise specified, these are the return vals for most functions:
- *
- *  0 -> success
- * -1 -> more bytes needed.
- * -2 -> failure; abort the load
- * -3 -> control needs to be passed back to the main loop
- *        \_ (most of the time returning 0 will get this, but not always)
- */
-
-
-
 /* Changes the stage to be GIF_GET_COLORMAP */
 static void
 gif_set_get_colormap (GifContext *context)
 {
-       context->colormap_flag = TRUE;
-       context->colormap_index = 0;
+       context->global_colormap_size = 0;
        context->state = GIF_GET_COLORMAP;
 }
 
 static void
 gif_set_get_colormap2 (GifContext *context)
 {
-       context->colormap_flag = TRUE;
-       context->colormap_index = 0;
+       context->frame_colormap_size = 0;
        context->state = GIF_GET_COLORMAP2;
 }
 
@@ -230,21 +278,44 @@ gif_get_colormap (GifContext *context)
 {
        unsigned char rgb[3];
 
-       while (context->colormap_index < context->bit_pixel) {
-               if (!ReadOK (context, rgb, sizeof (rgb))) {
-                       /*g_message (_("GIF: bad colormap\n"));*/
+       while (context->global_colormap_size < context->global_bit_pixel) {
+               if (!gif_read (context, rgb, sizeof (rgb))) {
                        return -1;
                }
 
-               context->color_map[CM_RED][context->colormap_index] = rgb[0];
-               context->color_map[CM_GREEN][context->colormap_index] = rgb[1];
-               context->color_map[CM_BLUE][context->colormap_index] = rgb[2];
+               context->global_color_map[0][context->global_colormap_size] = rgb[0];
+               context->global_color_map[1][context->global_colormap_size] = rgb[1];
+               context->global_color_map[2][context->global_colormap_size] = rgb[2];
 
-               context->colormap_flag &= (rgb[0] == rgb[1] && rgb[1] == rgb[2]);
-               context->colormap_index ++;
+                if (context->global_colormap_size == context->background_index) {
+                        context->animation->bg_red = rgb[0];
+                        context->animation->bg_green = rgb[1];
+                        context->animation->bg_blue = rgb[2];
+                }
+
+               context->global_colormap_size ++;
        }
 
-       context->gray_scale = (context->colormap_flag) ? GRAYSCALE : COLOR;
+       return 0;
+}
+
+
+static gint
+gif_get_colormap2 (GifContext *context)
+{
+       unsigned char rgb[3];
+
+       while (context->frame_colormap_size < context->frame_bit_pixel) {
+               if (!gif_read (context, rgb, sizeof (rgb))) {
+                       return -1;
+               }
+
+               context->frame_color_map[0][context->frame_colormap_size] = rgb[0];
+               context->frame_color_map[1][context->frame_colormap_size] = rgb[1];
+               context->frame_color_map[2][context->frame_colormap_size] = rgb[2];
+
+               context->frame_colormap_size ++;
+       }
 
        return 0;
 }
@@ -267,7 +338,7 @@ get_data_block (GifContext *context,
 {
 
        if (context->block_count == 0) {
-               if (!ReadOK (context, &context->block_count, 1)) {
+               if (!gif_read (context, &context->block_count, 1)) {
                        return -1;
                }
        }
@@ -278,7 +349,7 @@ get_data_block (GifContext *context,
                        return 0;
                }
 
-       if (!ReadOK (context, buf, context->block_count)) {
+       if (!gif_read (context, buf, context->block_count)) {
                return -1;
        }
 
@@ -288,9 +359,9 @@ get_data_block (GifContext *context,
 static void
 gif_set_get_extension (GifContext *context)
 {
-       context->state = GIF_GET_EXTENTION;
+       context->state = GIF_GET_EXTENSION;
        context->extension_flag = TRUE;
-       context->extension_label = '\000';
+       context->extension_label = 0;
        context->block_count = 0;
        context->block_ptr = 0;
 }
@@ -302,43 +373,79 @@ gif_get_extension (GifContext *context)
        gint empty_block = FALSE;
 
        if (context->extension_flag) {
-               if (!context->extension_label) {
-                       if (!ReadOK (context, &context->extension_label , 1)) {
+               if (context->extension_label == 0) {
+                       /* I guess bad things can happen if we have an extension of 0 )-: */
+                       /* I should look into this sometime */
+                       if (!gif_read (context, & context->extension_label , 1)) {
                                return -1;
                        }
                }
 
                switch (context->extension_label) {
-               case 0xf9:                      /* Graphic Control Extension */
-                       retval = get_data_block (context, (unsigned char *) context->block_buf, NULL);
+                case 0xf9:                     /* Graphic Control Extension */
+                        retval = get_data_block (context, (unsigned char *) context->block_buf, NULL);
                        if (retval != 0)
                                return retval;
-                       context->gif89.disposal = (context->block_buf[0] >> 2) & 0x7;
-                       context->gif89.input_flag = (context->block_buf[0] >> 1) & 0x1;
-                       context->gif89.delay_time = LM_to_uint (context->block_buf[1], context->block_buf[2]);
-                       if (context->pixbuf == NULL) {
+
+                       if (context->frame == NULL) {
                                /* I only want to set the transparency if I haven't
-                                * created the pixbuf yet. */
-                               if ((context->block_buf[0] & 0x1) != 0)
+                                * created the frame yet.
+                                 */
+                               context->gif89.disposal = (context->block_buf[0] >> 2) & 0x7;
+                               context->gif89.input_flag = (context->block_buf[0] >> 1) & 0x1;
+                               context->gif89.delay_time = LM_to_uint (context->block_buf[1], context->block_buf[2]);
+                               
+                               if ((context->block_buf[0] & 0x1) != 0) {
                                        context->gif89.transparent = context->block_buf[3];
-                               else
+                               } else {
                                        context->gif89.transparent = -1;
+                               }
                        }
-                       
+
                        /* Now we've successfully loaded this one, we continue on our way */
                        context->block_count = 0;
                        context->extension_flag = FALSE;
+                       break;
+                case 0xff: /* application extension */
+                        if (!context->in_loop_extension) { 
+                                retval = get_data_block (context, (unsigned char *) context->block_buf, NULL);
+                                if (retval != 0)
+                                        return retval;
+                                if (!strncmp ((gchar *)context->block_buf, "NETSCAPE2.0", 11) ||
+                                    !strncmp ((gchar *)context->block_buf, "ANIMEXTS1.0", 11)) {
+                                        context->in_loop_extension = TRUE;
+                                }
+                                context->block_count = 0;
+                        }
+                        if (context->in_loop_extension) {
+                                do {
+                                        retval = get_data_block (context, (unsigned char *) context->block_buf, &empty_block);
+                                        if (retval != 0)
+                                                return retval;
+                                        if (context->block_buf[0] == 0x01) {
+                                                context->animation->loop = context->block_buf[1] + (context->block_buf[2] << 8);
+                                                if (context->animation->loop != 0) 
+                                                        context->animation->loop++;
+                                        }
+                                        context->block_count = 0;
+                                }
+                                while (!empty_block);
+                                context->in_loop_extension = FALSE;
+                                context->extension_flag = FALSE;
+                                return 0;
+                        }
+                       break;                          
                default:
                        /* Unhandled extension */
                        break;
                }
        }
-       /* read all blocks, until I get an empty block */
-       /* not sure why, but it makes it work.  -jrb */
+       /* read all blocks, until I get an empty block, in case there was an extension I didn't know about. */
        do {
                retval = get_data_block (context, (unsigned char *) context->block_buf, &empty_block);
                if (retval != 0)
                        return retval;
+               context->block_count = 0;
        } while (!empty_block);
 
        return 0;
@@ -350,16 +457,16 @@ static int
 GetDataBlock (GifContext *context,
              unsigned char *buf)
 {
-//     unsigned char count;
+/*     unsigned char count; */
 
-       if (!ReadOK (context, &context->block_count, 1)) {
+       if (!gif_read (context, &context->block_count, 1)) {
                /*g_message (_("GIF: error in getting DataBlock size\n"));*/
                return -1;
        }
 
        ZeroDataBlock = context->block_count == 0;
 
-       if ((context->block_count != 0) && (!ReadOK (context, buf, context->block_count))) {
+       if ((context->block_count != 0) && (!gif_read (context, buf, context->block_count))) {
                /*g_message (_("GIF: error in reading DataBlock\n"));*/
                return -1;
        }
@@ -367,51 +474,12 @@ GetDataBlock (GifContext *context,
        return context->block_count;
 }
 
-#if 0
-
-static int
-GetCode (GifContext *context,
-        int   code_size)
-{
-       int i, j, ret;
-       unsigned char count;
-
-
-       if ((context->code_curbit + code_size) >= context->code_lastbit){
-               if (context->code_done) {
-                       if (context->code_curbit >= context->code_lastbit) {
-                               /*g_message (_("GIF: ran off the end of by bits\n"));*/
-                               return -2;
-                       }
-                       return -2;
-               }
-               context->block_buf[0] = context->block_buf[context->code_last_byte - 2];
-               context->block_buf[1] = context->block_buf[context->code_last_byte - 1];
-
-               context->block_count = 0;
-               
-               if ((count = GetDataBlock (context, &context->block_buf[2])) == 0)
-                       context->code_done = TRUE;
-
-               context->code_last_byte = 2 + count;
-               context->code_curbit = (context->code_curbit - context->code_lastbit) + 16;
-               context->code_lastbit = (2 + count) * 8;
-       }
-
-       ret = 0;
-       for (i = context->code_curbit, j = 0; j < code_size; ++i, ++j)
-               ret |= ((context->block_buf[i / 8] & (1 << (i % 8))) != 0) << j;
-
-       context->code_curbit += code_size;
-
-       return ret;
-}
-#endif
 
 static void
 gif_set_lzw_fill_buffer (GifContext *context)
 {
        context->block_count = 0;
+       context->old_state = context->state;
        context->state = GIF_LZW_FILL_BUFFER;
 }
 
@@ -419,13 +487,24 @@ static int
 gif_lzw_fill_buffer (GifContext *context)
 {
        gint retval;
-       
+
        if (context->code_done) {
                if (context->code_curbit >= context->code_lastbit) {
-                               g_message ("GIF: ran off the end of by bits\n");
+                        g_set_error_literal (context->error,
+                                             GDK_PIXBUF_ERROR,
+                                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                             _("GIF file was missing some data (perhaps it was truncated somehow?)"));
+
                        return -2;
                }
-               g_message ("trying to read more data after we've done stuff\n");
+                /* Is this supposed to be an error or what? */
+               /* g_message ("trying to read more data after we've done stuff\n"); */
+                g_set_error (context->error,
+                             GDK_PIXBUF_ERROR,
+                             GDK_PIXBUF_ERROR_FAILED,
+                             _("Internal error in the GIF loader (%s)"),
+                             G_STRLOC);
+                
                return -2;
        }
 
@@ -444,13 +523,13 @@ gif_lzw_fill_buffer (GifContext *context)
        context->code_curbit = (context->code_curbit - context->code_lastbit) + 16;
        context->code_lastbit = (2 + context->block_count) * 8;
 
-       context->state = GIF_GET_LZW;
+       context->state = context->old_state;
        return 0;
 }
 
 static int
-GetCode (GifContext *context,
-        int   code_size)
+get_code (GifContext *context,
+         int   code_size)
 {
        int i, j, ret;
 
@@ -468,109 +547,164 @@ GetCode (GifContext *context,
        return ret;
 }
 
-/*
- * For various reasons, this one is a little different from the others:
- *
- * returns -1 if it needs more bytes.
- * returns -2 if there's an error.
- * returns -3 if there is no error, but needs to go back to the main loop.
- * returns the byte otherwise.
- */
+
+static void
+set_gif_lzw_clear_code (GifContext *context)
+{
+       context->state = GIF_LZW_CLEAR_CODE;
+       context->lzw_code_pending = -1;
+}
 
 static int
-lwz_read_byte (GifContext *context)
+gif_lzw_clear_code (GifContext *context)
+{
+       gint code;
+
+       code = get_code (context, context->lzw_code_size);
+       if (code == -3)
+               return -0;
+
+       context->lzw_firstcode = context->lzw_oldcode = code;
+       context->lzw_code_pending = code;
+       context->state = GIF_GET_LZW;
+       return 0;
+}
+
+#define CHECK_LZW_SP() G_STMT_START {                                           \
+        if ((guchar *)context->lzw_sp >=                                        \
+            (guchar *)context->lzw_stack + sizeof (context->lzw_stack)) {       \
+                 g_set_error_literal (context->error,                           \
+                                      GDK_PIXBUF_ERROR,                         \
+                                      GDK_PIXBUF_ERROR_CORRUPT_IMAGE,           \
+                                      _("Stack overflow"));                     \
+                return -2;                                                      \
+        }                                                                       \
+} G_STMT_END
+
+static int
+lzw_read_byte (GifContext *context)
 {
        int code, incode;
        gint retval;
+       gint my_retval;
        register int i;
 
-       if (context->lwz_fresh) {
-               context->lwz_fresh = FALSE;
+       if (context->lzw_code_pending != -1) {
+               retval = context->lzw_code_pending;
+               context->lzw_code_pending = -1;
+               return retval;
+       }
+
+       if (context->lzw_fresh) {
+               context->lzw_fresh = FALSE;
                do {
-                       retval = GetCode (context, context->lwz_code_size);
+                       retval = get_code (context, context->lzw_code_size);
                        if (retval < 0) {
                                return retval;
                        }
-                       
-                       context->lwz_firstcode = context->lwz_oldcode = retval;
-               } while (context->lwz_firstcode == context->lwz_clear_code);
-               return context->lwz_firstcode;
+
+                       context->lzw_firstcode = context->lzw_oldcode = retval;
+               } while (context->lzw_firstcode == context->lzw_clear_code);
+               return context->lzw_firstcode;
        }
 
-       if (context->lwz_sp > context->lwz_stack)
-               return *--(context->lwz_sp);
+       if (context->lzw_sp > context->lzw_stack) {
+               my_retval = *--(context->lzw_sp);
+               return my_retval;
+       }
 
-       while ((code = GetCode (context, context->lwz_code_size)) >= 0) {
-               if (code == context->lwz_clear_code) {
-                       for (i = 0; i < context->lwz_clear_code; ++i) {
-                               context->lwz_table[0][i] = 0;
-                               context->lwz_table[1][i] = i;
+       while ((code = get_code (context, context->lzw_code_size)) >= 0) {
+               if (code == context->lzw_clear_code) {
+                       for (i = 0; i < context->lzw_clear_code; ++i) {
+                               context->lzw_table[0][i] = 0;
+                               context->lzw_table[1][i] = i;
                        }
-                       for (; i < (1 << MAX_LWZ_BITS); ++i)
-                               context->lwz_table[0][i] = context->lwz_table[1][i] = 0;
-                       context->lwz_code_size = context->lwz_set_code_size + 1;
-                       context->lwz_max_code_size = 2 * context->lwz_clear_code;
-                       context->lwz_max_code = context->lwz_clear_code + 2;
-                       context->lwz_sp = context->lwz_stack;
-                       context->lwz_firstcode = context->lwz_oldcode =
-                               GetCode (context, context->lwz_code_size);
-                       return context->lwz_firstcode;
-               } else if (code == context->lwz_end_code) {
+                       for (; i < (1 << MAX_LZW_BITS); ++i)
+                               context->lzw_table[0][i] = context->lzw_table[1][i] = 0;
+                       context->lzw_code_size = context->lzw_set_code_size + 1;
+                       context->lzw_max_code_size = 2 * context->lzw_clear_code;
+                       context->lzw_max_code = context->lzw_clear_code + 2;
+                       context->lzw_sp = context->lzw_stack;
+
+                       set_gif_lzw_clear_code (context);
+                       return -3;
+               } else if (code == context->lzw_end_code) {
                        int count;
                        unsigned char buf[260];
 
-                       g_error (" DID WE EVER EVER GET HERE\n");
-                       
-                       if (ZeroDataBlock)
+                        /*  FIXME - we should handle this case */
+                        g_set_error_literal (context->error,
+                                             GDK_PIXBUF_ERROR,
+                                             GDK_PIXBUF_ERROR_FAILED,
+                                             _("GIF image loader cannot understand this image."));
+                        return -2;
+                        
+                       if (ZeroDataBlock) {
                                return -2;
+                       }
 
                        while ((count = GetDataBlock (context, buf)) > 0)
                                ;
 
-                       if (count != 0)
+                       if (count != 0) {
                                /*g_print (_("GIF: missing EOD in data stream (common occurence)"));*/
-                       return -2;
+                               return -2;
+                       }
                }
 
                incode = code;
 
-               if (code >= context->lwz_max_code) {
-                       *(context->lwz_sp)++ = context->lwz_firstcode;
-                       code = context->lwz_oldcode;
+               if (code >= context->lzw_max_code) {
+                        CHECK_LZW_SP ();
+                       *(context->lzw_sp)++ = context->lzw_firstcode;
+                       code = context->lzw_oldcode;
                }
 
-               while (code >= context->lwz_clear_code) {
-                       *(context->lwz_sp)++ = context->lwz_table[1][code];
-                       if (code == context->lwz_table[0][code]) {
-                               /*g_message (_("GIF: circular table entry BIG ERROR\n"));*/
-                               /*gimp_quit ();*/
+               while (code >= context->lzw_clear_code) {
+                        if (code >= (1 << MAX_LZW_BITS)) {
+                                g_set_error_literal (context->error,
+                                                     GDK_PIXBUF_ERROR,
+                                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                                     _("Bad code encountered"));
+                               return -2;
+                        }
+                        CHECK_LZW_SP ();
+                       *(context->lzw_sp)++ = context->lzw_table[1][code];
+
+                       if (code == context->lzw_table[0][code]) {
+                                g_set_error_literal (context->error,
+                                                     GDK_PIXBUF_ERROR,
+                                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                                     _("Circular table entry in GIF file"));
                                return -2;
                        }
-                       code = context->lwz_table[0][code];
+                       code = context->lzw_table[0][code];
                }
 
-               *(context->lwz_sp)++ = context->lwz_firstcode = context->lwz_table[1][code];
-
-               if ((code = context->lwz_max_code) < (1 << MAX_LWZ_BITS)) {
-                       context->lwz_table[0][code] = context->lwz_oldcode;
-                       context->lwz_table[1][code] = context->lwz_firstcode;
-                       ++context->lwz_max_code;
-                       if ((context->lwz_max_code >= context->lwz_max_code_size) &&
-                           (context->lwz_max_code_size < (1 << MAX_LWZ_BITS))) {
-                               context->lwz_max_code_size *= 2;
-                               ++context->lwz_code_size;
+                CHECK_LZW_SP ();
+               *(context->lzw_sp)++ = context->lzw_firstcode = context->lzw_table[1][code];
+
+               if ((code = context->lzw_max_code) < (1 << MAX_LZW_BITS)) {
+                       context->lzw_table[0][code] = context->lzw_oldcode;
+                       context->lzw_table[1][code] = context->lzw_firstcode;
+                       ++context->lzw_max_code;
+                       if ((context->lzw_max_code >= context->lzw_max_code_size) &&
+                           (context->lzw_max_code_size < (1 << MAX_LZW_BITS))) {
+                               context->lzw_max_code_size *= 2;
+                               ++context->lzw_code_size;
                        }
                }
 
-               context->lwz_oldcode = incode;
+               context->lzw_oldcode = incode;
 
-               if (context->lwz_sp > context->lwz_stack)
-                       return *--(context->lwz_sp);
+               if (context->lzw_sp > context->lzw_stack) {
+                       my_retval = *--(context->lzw_sp);
+                       return my_retval;
+               }
        }
        return code;
 }
 
-
 static void
 gif_set_get_lzw (GifContext *context)
 {
@@ -580,46 +714,298 @@ gif_set_get_lzw (GifContext *context)
        context->draw_pass = 0;
 }
 
+static void
+gif_fill_in_pixels (GifContext *context, guchar *dest, gint offset, guchar v)
+{
+       guchar *pixel = NULL;
+        guchar (*cmap)[MAXCOLORMAPSIZE];
+
+        if (context->frame_cmap_active)
+                cmap = context->frame_color_map;
+        else
+                cmap = context->global_color_map;
+        
+       if (context->gif89.transparent != -1) {
+               pixel = dest + (context->draw_ypos + offset) * gdk_pixbuf_get_rowstride (context->frame->pixbuf) + context->draw_xpos * 4;
+               *pixel = cmap [0][(guchar) v];
+               *(pixel+1) = cmap [1][(guchar) v];
+               *(pixel+2) = cmap [2][(guchar) v];
+               *(pixel+3) = (guchar) ((v == context->gif89.transparent) ? 0 : 255);
+       } else {
+               pixel = dest + (context->draw_ypos + offset) * gdk_pixbuf_get_rowstride (context->frame->pixbuf) + context->draw_xpos * 3;
+               *pixel = cmap [0][(guchar) v];
+               *(pixel+1) = cmap [1][(guchar) v];
+               *(pixel+2) = cmap [2][(guchar) v];
+       }
+}
+
+
+/* only called if progressive and interlaced */
+static void
+gif_fill_in_lines (GifContext *context, guchar *dest, guchar v)
+{
+       switch (context->draw_pass) {
+       case 0:
+               if (context->draw_ypos > 4) {
+                       gif_fill_in_pixels (context, dest, -4, v);
+                       gif_fill_in_pixels (context, dest, -3, v);
+               }
+               if (context->draw_ypos < (context->frame_height - 4)) {
+                       gif_fill_in_pixels (context, dest, 3, v);
+                       gif_fill_in_pixels (context, dest, 4, v);
+               }
+               /* we don't need a break here.  We draw the outer pixels first, then the
+                * inner ones, then the innermost ones.  case 0 needs to draw all 3 bands.
+                * case 1, just the last two, and case 2 just draws the last one*/
+       case 1:
+               if (context->draw_ypos > 2)
+                       gif_fill_in_pixels (context, dest, -2, v);
+               if (context->draw_ypos < (context->frame_height - 2))
+                       gif_fill_in_pixels (context, dest, 2, v);
+               /* no break as above. */
+       case 2:
+               if (context->draw_ypos > 1)
+                       gif_fill_in_pixels (context, dest, -1, v);
+               if (context->draw_ypos < (context->frame_height - 1))
+                       gif_fill_in_pixels (context, dest, 1, v);
+       case 3:
+       default:
+               break;
+       }
+}
+
+/* Clips a rectancle to the base dimensions. Returns TRUE if the clipped rectangle is non-empty. */
+static gboolean
+clip_frame (GifContext *context, 
+            gint       *x, 
+            gint       *y, 
+            gint       *width, 
+            gint       *height)
+{
+        gint orig_x, orig_y;
+        
+        orig_x = *x;
+        orig_y = *y;
+       *x = MAX (0, *x);
+       *y = MAX (0, *y);
+       *width = MIN (context->width, orig_x + *width) - *x;
+       *height = MIN (context->height, orig_y + *height) - *y;
+
+       if (*width > 0 && *height > 0)
+               return TRUE;
+
+       /* The frame is completely off-bounds */
+
+       *x = 0;
+       *y = 0;
+       *width = 0;
+       *height = 0;
+
+        return FALSE;
+}
+
+/* Call update_func on the given rectangle, unless it is completely off-bounds */
+static void
+maybe_update (GifContext *context,
+              gint        x,
+              gint        y,
+              gint        width,
+              gint        height)
+{
+        if (clip_frame (context, &x, &y, &width, &height))
+                (*context->update_func) (context->frame->pixbuf, 
+                                         x, y, width, height,
+                                         context->user_data);
+}
+
 static int
 gif_get_lzw (GifContext *context)
 {
        guchar *dest, *temp;
+       gint lower_bound, upper_bound; /* bounds for emitting the area_updated signal */
+       gboolean bound_flag;
+       gint first_pass; /* bounds for emitting the area_updated signal */
        gint v;
 
-       
-       if (context->pixbuf == NULL) {
-               context->pixbuf = gdk_pixbuf_new (ART_PIX_RGB,
-                                                 context->gif89.transparent,
-                                                 8,
-                                                 context->width,
-                                                 context->height);
-
-               if (context->func)
-                       (* context->func) (context->pixbuf, context->user_data);
-       }
+       if (context->frame == NULL) {
+                context->frame = g_new (GdkPixbufFrame, 1);
+
+                context->frame->composited = NULL;
+                context->frame->revert = NULL;
+                
+                if (context->frame_len == 0 || context->frame_height == 0) {
+                        /* An empty frame, we just output a single transparent
+                         * pixel at (0, 0).
+                         */
+                        context->x_offset = 0;
+                        context->y_offset = 0;
+                        context->frame_len = 1;
+                        context->frame_height = 1;
+                        context->frame->pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, TRUE, 8, 1, 1);
+                        if (context->frame->pixbuf) {
+                                guchar *pixels;
+
+                                pixels = gdk_pixbuf_get_pixels (context->frame->pixbuf);
+                                pixels[0] = 0;
+                                pixels[1] = 0;
+                                pixels[2] = 0;
+                                pixels[3] = 0;
+                        }
+                } else
+                        context->frame->pixbuf =
+                                gdk_pixbuf_new (GDK_COLORSPACE_RGB,
+                                                TRUE,
+                                                8,
+                                                context->frame_len,
+                                                context->frame_height);
+                if (!context->frame->pixbuf) {
+                        g_free (context->frame);
+                        g_set_error_literal (context->error,
+                                             GDK_PIXBUF_ERROR,
+                                             GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
+                                             _("Not enough memory to load GIF file"));
+                        return -2;
+                }
+
+                context->frame->x_offset = context->x_offset;
+                context->frame->y_offset = context->y_offset;
+                context->frame->need_recomposite = TRUE;
+                
+                /* GIF delay is in hundredths, we want thousandths */
+                context->frame->delay_time = context->gif89.delay_time * 10;
+
+                /* GIFs with delay time 0 are mostly broken, but they
+                 * just want a default, "not that fast" delay.
+                 */
+                if (context->frame->delay_time == 0)
+                        context->frame->delay_time = 100;
+
+                /* No GIFs gets to play faster than 50 fps. They just
+                 * lock up poor gtk.
+                 */
+                if (context->frame->delay_time < 20)
+                        context->frame->delay_time = 20; /* 20 = "fast" */
+                
+                context->frame->elapsed = context->animation->total_time;
+                context->animation->total_time += context->frame->delay_time;                
+                
+                switch (context->gif89.disposal) {
+                case 0:
+                case 1:
+                        context->frame->action = GDK_PIXBUF_FRAME_RETAIN;
+                        break;
+                case 2:
+                        context->frame->action = GDK_PIXBUF_FRAME_DISPOSE;
+                        break;
+                case 3:
+                        context->frame->action = GDK_PIXBUF_FRAME_REVERT;
+                        break;
+                default:
+                        context->frame->action = GDK_PIXBUF_FRAME_RETAIN;
+                        break;
+                }
+
+                context->frame->bg_transparent = (context->gif89.transparent == context->background_index);
+                
+                context->animation->n_frames ++;
+                context->animation->frames = g_list_append (context->animation->frames, context->frame);
+
+                /* Only call prepare_func for the first frame */
+               if (context->animation->frames->next == NULL) { 
+                        if (context->animation->width == 0 )
+                                context->animation->width = gdk_pixbuf_get_width(context->frame->pixbuf);
+                        if (context->animation->height == 0)
+                                context->animation->height = gdk_pixbuf_get_height (context->frame->pixbuf);
+
+                        if (context->prepare_func)
+                                (* context->prepare_func) (context->frame->pixbuf,
+                                                           GDK_PIXBUF_ANIMATION (context->animation),
+                                                           context->user_data);
+                } else {
+                        /* Otherwise init frame with last frame */
+                        GList *link;
+                        GdkPixbufFrame *prev_frame;
+                        gint x, y, w, h;
+                        
+                        link = g_list_find (context->animation->frames, context->frame);
+
+                        prev_frame = link->prev->data;
+
+                        gdk_pixbuf_gif_anim_frame_composite (context->animation, prev_frame);
+
+                        /* Composite failed */
+                        if (prev_frame->composited == NULL) {
+                                GdkPixbufFrame *frame = NULL;
+                                link = g_list_first (context->animation->frames);
+                                while (link != NULL) {
+                                        frame = (GdkPixbufFrame *)link->data;
+                                        if (frame != NULL) {
+                                                if (frame->pixbuf != NULL)
+                                                        g_object_unref (frame->pixbuf);
+                                                if (frame->composited != NULL)
+                                                        g_object_unref (frame->composited);
+                                                if (frame->revert != NULL)
+                                                        g_object_unref (frame->revert);
+                                                g_free (frame);
+                                        }
+                                        link = link->next;
+                                }
+                                
+                                g_list_free (context->animation->frames);
+                                context->animation->frames = NULL;
+                                
+                                g_set_error_literal (context->error,
+                                                     GDK_PIXBUF_ERROR,
+                                                     GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
+                                                     _("Not enough memory to composite a frame in GIF file"));
+                                return -2;
+                        }
+                    
+                        x = context->frame->x_offset;
+                        y = context->frame->y_offset;
+                        w = gdk_pixbuf_get_width (context->frame->pixbuf);
+                        h = gdk_pixbuf_get_height (context->frame->pixbuf);
+                        if (clip_frame (context, &x, &y, &w, &h))
+                                gdk_pixbuf_copy_area (prev_frame->composited,
+                                                      x, y, w, h,
+                                                      context->frame->pixbuf,
+                                                      0, 0);
+                }
+        }
+
+       dest = gdk_pixbuf_get_pixels (context->frame->pixbuf);
+
+       bound_flag = FALSE;
+       lower_bound = upper_bound = context->draw_ypos;
+       first_pass = context->draw_pass;
 
-       dest = gdk_pixbuf_get_pixels (context->pixbuf);
        while (TRUE) {
-               v = lwz_read_byte (context);
+                guchar (*cmap)[MAXCOLORMAPSIZE];
+
+                if (context->frame_cmap_active)
+                        cmap = context->frame_color_map;
+                else
+                        cmap = context->global_color_map;
+                
+               v = lzw_read_byte (context);
                if (v < 0) {
-                       return v;
-               }
-               
-
-               if (context->gif89.transparent) {
-                       temp = dest + context->draw_ypos * gdk_pixbuf_get_rowstride (context->pixbuf) + context->draw_xpos * 4;
-                       *temp = context->color_map [0][(guchar) v];
-                       *(temp+1) = context->color_map [1][(guchar) v];
-                       *(temp+2) = context->color_map [2][(guchar) v];
-                       *(temp+3) = (guchar) ((v == context->gif89.transparent) ? 0 : 65535);
-               } else {
-                       temp = dest + context->draw_ypos * gdk_pixbuf_get_rowstride (context->pixbuf) + context->draw_xpos * 3;
-                       *temp = context->color_map [0][(guchar) v];
-                       *(temp+1) = context->color_map [1][(guchar) v];
-                       *(temp+2) = context->color_map [2][(guchar) v];
+                       goto finished_data;
                }
+               bound_flag = TRUE;
+
+                g_assert (gdk_pixbuf_get_has_alpha (context->frame->pixbuf));
+                
+                temp = dest + context->draw_ypos * gdk_pixbuf_get_rowstride (context->frame->pixbuf) + context->draw_xpos * 4;
+                *temp = cmap [0][(guchar) v];
+                *(temp+1) = cmap [1][(guchar) v];
+                *(temp+2) = cmap [2][(guchar) v];
+                *(temp+3) = (guchar) ((v == context->gif89.transparent) ? 0 : 255);
+
+               if (context->prepare_func && context->frame_interlace)
+                       gif_fill_in_lines (context, dest, v);
 
                context->draw_xpos++;
+                
                if (context->draw_xpos == context->frame_len) {
                        context->draw_xpos = 0;
                        if (context->frame_interlace) {
@@ -655,49 +1041,120 @@ gif_get_lzw (GifContext *context)
                        } else {
                                context->draw_ypos++;
                        }
+                       if (context->draw_pass != first_pass) {
+                               if (context->draw_ypos > lower_bound) {
+                                       lower_bound = 0;
+                                       upper_bound = context->frame_height;
+                               } else {
+                                        
+                               }
+                       } else
+                               upper_bound = context->draw_ypos;
                }
                if (context->draw_ypos >= context->frame_height)
                        break;
        }
+
  done:
-       /* we got enough data. there may be more (ie, newer layers) but we can quit now */
-       context->state = GIF_DONE;
-       return 0;
+
+        context->state = GIF_GET_NEXT_STEP;
+
+        v = 0;
+
+ finished_data:
+        
+        if (bound_flag)
+                context->frame->need_recomposite = TRUE;
+        
+       if (bound_flag && context->update_func) {
+               if (lower_bound <= upper_bound && first_pass == context->draw_pass) {
+                        maybe_update (context, 
+                                      context->frame->x_offset,
+                                      context->frame->y_offset + lower_bound,
+                                      gdk_pixbuf_get_width (context->frame->pixbuf),
+                                      upper_bound - lower_bound);
+               } else {
+                       if (lower_bound <= upper_bound) {
+                                maybe_update (context,
+                                              context->frame->x_offset,
+                                              context->frame->y_offset,
+                                              gdk_pixbuf_get_width (context->frame->pixbuf),
+                                              gdk_pixbuf_get_height (context->frame->pixbuf));
+                       } else {
+                                maybe_update (context,
+                                              context->frame->x_offset,
+                                              context->frame->y_offset,
+                                              gdk_pixbuf_get_width (context->frame->pixbuf),
+                                              upper_bound);
+                                maybe_update (context,
+                                              context->frame->x_offset,
+                                              context->frame->y_offset + lower_bound,
+                                              gdk_pixbuf_get_width (context->frame->pixbuf),
+                                              gdk_pixbuf_get_height (context->frame->pixbuf) - lower_bound);
+                       }
+               }
+       }
+
+       if (context->state == GIF_GET_NEXT_STEP) {
+                /* Will be freed with context->animation, we are just
+                 * marking that we're done with it (no current frame)
+                 */
+               context->frame = NULL;
+                context->frame_cmap_active = FALSE;
+
+                if (context->stop_after_first_frame)
+                        context->state =  GIF_DONE;
+       }
+       
+       return v;
 }
 
 static void
 gif_set_prepare_lzw (GifContext *context)
 {
        context->state = GIF_PREPARE_LZW;
+       context->lzw_code_pending = -1;
 }
 static int
 gif_prepare_lzw (GifContext *context)
 {
        gint i;
 
-       if (!ReadOK (context, &(context->lwz_set_code_size), 1)) {
+       if (!gif_read (context, &(context->lzw_set_code_size), 1)) {
                /*g_message (_("GIF: EOF / read error on image data\n"));*/
                return -1;
        }
-
-       context->lwz_code_size = context->lwz_set_code_size + 1;
-       context->lwz_clear_code = 1 << context->lwz_set_code_size;
-       context->lwz_end_code = context->lwz_clear_code + 1;
-       context->lwz_max_code_size = 2 * context->lwz_clear_code;
-       context->lwz_max_code = context->lwz_clear_code + 2;
-       context->lwz_fresh = TRUE;
+        
+        if (context->lzw_set_code_size > MAX_LZW_BITS) {
+                g_set_error_literal (context->error,
+                                     GDK_PIXBUF_ERROR,
+                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                     _("GIF image is corrupt (incorrect LZW compression)"));
+                return -2;
+        }
+
+       context->lzw_code_size = context->lzw_set_code_size + 1;
+       context->lzw_clear_code = 1 << context->lzw_set_code_size;
+       context->lzw_end_code = context->lzw_clear_code + 1;
+       context->lzw_max_code_size = 2 * context->lzw_clear_code;
+       context->lzw_max_code = context->lzw_clear_code + 2;
+       context->lzw_fresh = TRUE;
        context->code_curbit = 0;
        context->code_lastbit = 0;
+       context->code_last_byte = 0;
        context->code_done = FALSE;
 
-       for (i = 0; i < context->lwz_clear_code; ++i) {
-               context->lwz_table[0][i] = 0;
-               context->lwz_table[1][i] = i;
+        g_assert (context->lzw_clear_code <= 
+                  G_N_ELEMENTS (context->lzw_table[0]));
+
+       for (i = 0; i < context->lzw_clear_code; ++i) {
+               context->lzw_table[0][i] = 0;
+               context->lzw_table[1][i] = i;
        }
-       for (; i < (1 << MAX_LWZ_BITS); ++i)
-               context->lwz_table[0][i] = context->lwz_table[1][0] = 0;
+       for (; i < (1 << MAX_LZW_BITS); ++i)
+               context->lzw_table[0][i] = context->lzw_table[1][0] = 0;
 
-       context->lwz_sp = context->lwz_stack;
+       context->lzw_sp = context->lzw_stack;
        gif_set_get_lzw (context);
 
        return 0;
@@ -710,14 +1167,20 @@ gif_init (GifContext *context)
        unsigned char buf[16];
        char version[4];
 
-       if (!ReadOK (context, buf, 6)) {
-               /* Unable to read magic number */
+       if (!gif_read (context, buf, 6)) {
+               /* Unable to read magic number,
+                 * gif_read() should have set error
+                 */
                return -1;
        }
 
        if (strncmp ((char *) buf, "GIF", 3) != 0) {
                /* Not a GIF file */
-               return -1;
+                g_set_error_literal (context->error,
+                                     GDK_PIXBUF_ERROR,
+                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                     _("File does not appear to be a GIF file"));
+               return -2;
        }
 
        strncpy (version, (char *) buf + 3, 3);
@@ -725,28 +1188,55 @@ gif_init (GifContext *context)
 
        if ((strcmp (version, "87a") != 0) && (strcmp (version, "89a") != 0)) {
                /* bad version number, not '87a' or '89a' */
-               return -1;
+                g_set_error (context->error,
+                             GDK_PIXBUF_ERROR,
+                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                             _("Version %s of the GIF file format is not supported"),
+                             version);
+               return -2;
        }
 
        /* read the screen descriptor */
-       if (!ReadOK (context, buf, 7)) {
-               /* Failed to read screen descriptor */
+       if (!gif_read (context, buf, 7)) {
+               /* Failed to read screen descriptor, error set */
                return -1;
        }
 
        context->width = LM_to_uint (buf[0], buf[1]);
        context->height = LM_to_uint (buf[2], buf[3]);
-       context->bit_pixel = 2 << (buf[4] & 0x07);
-       context->color_resolution = (((buf[4] & 0x70) >> 3) + 1);
-       context->background = buf[5];
+        /* The 4th byte is
+         * high bit: whether to use the background index
+         * next 3:   color resolution
+         * next:     whether colormap is sorted by priority of allocation
+         * last 3:   size of colormap
+         */
+       context->global_bit_pixel = 2 << (buf[4] & 0x07);
+       context->global_color_resolution = (((buf[4] & 0x70) >> 3) + 1);
+        context->has_global_cmap = (buf[4] & 0x80) != 0;
+       context->background_index = buf[5];
        context->aspect_ratio = buf[6];
-       context->pixbuf = NULL;
 
-       if (BitSet (buf[4], LOCALCOLORMAP)) {
+        /* Use background of transparent black as default, though if
+         * one isn't set explicitly no one should ever use it.
+         */
+        context->animation->bg_red = 0;
+        context->animation->bg_green = 0;
+        context->animation->bg_blue = 0;
+
+        context->animation->width = context->width;
+        context->animation->height = context->height;
+
+       if (context->has_global_cmap) {
                gif_set_get_colormap (context);
        } else {
                context->state = GIF_GET_NEXT_STEP;
        }
+
+#ifdef DUMP_IMAGE_DETAILS
+        g_print (">Image width: %d height: %d global_cmap: %d background: %d\n",
+                 context->width, context->height, context->has_global_cmap, context->background_index);
+#endif
+        
        return 0;
 }
 
@@ -760,40 +1250,72 @@ static gint
 gif_get_frame_info (GifContext *context)
 {
        unsigned char buf[9];
-       if (!ReadOK (context, buf, 9)) {
+        
+       if (!gif_read (context, buf, 9)) {
                return -1;
        }
+        
        /* Okay, we got all the info we need.  Lets record it */
        context->frame_len = LM_to_uint (buf[4], buf[5]);
        context->frame_height = LM_to_uint (buf[6], buf[7]);
-       if (context->frame_height > context->height) {
-               context->state = GIF_DONE;
-               return -2;
+       context->x_offset = LM_to_uint (buf[0], buf[1]);
+       context->y_offset = LM_to_uint (buf[2], buf[3]);
+
+       if (context->animation->frames == NULL &&
+            context->gif89.disposal == 3) {
+                /* First frame can't have "revert to previous" as its
+                 * dispose mode. Silently use "retain" instead.
+                 */
+                context->gif89.disposal = 0;
        }
 
        context->frame_interlace = BitSet (buf[8], INTERLACE);
+
+#ifdef DUMP_IMAGE_DETAILS
+        g_print (">width: %d height: %d xoffset: %d yoffset: %d disposal: %d delay: %d transparent: %d interlace: %d\n",
+                 context->frame_len, context->frame_height, context->x_offset, context->y_offset,
+                 context->gif89.disposal, context->gif89.delay_time, context->gif89.transparent, context->frame_interlace);
+#endif
+        
        if (BitSet (buf[8], LOCALCOLORMAP)) {
+
+#ifdef DUMP_IMAGE_DETAILS
+                g_print (">has local colormap\n");
+#endif
+                
                /* Does this frame have it's own colormap. */
                /* really only relevant when looking at the first frame
                 * of an animated gif. */
                /* if it does, we need to re-read in the colormap,
                 * the gray_scale, and the bit_pixel */
-               context->bit_pixel = 1 << ((buf[8] & 0x07) + 1);
+                context->frame_cmap_active = TRUE;
+               context->frame_bit_pixel = 1 << ((buf[8] & 0x07) + 1);
                gif_set_get_colormap2 (context);
                return 0;
        }
+
+        if (!context->has_global_cmap) {
+                context->state = GIF_DONE;
+                
+                g_set_error_literal (context->error,
+                                     GDK_PIXBUF_ERROR,
+                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                     _("GIF image has no global colormap, and a frame inside it has no local colormap."));
+                
+               return -2;
+        }
+
        gif_set_prepare_lzw (context);
        return 0;
-       
-}
 
+}
 
 static gint
 gif_get_next_step (GifContext *context)
 {
        unsigned char c;
        while (TRUE) {
-               if (!ReadOK (context, &c, 1)) {
+               if (!gif_read (context, &c, 1)) {
                        return -1;
                }
                if (c == ';') {
@@ -801,13 +1323,13 @@ gif_get_next_step (GifContext *context)
                        /* hmm.  Not 100% sure what to do about this.  Should
                         * i try to return a blank image instead? */
                        context->state = GIF_DONE;
-                       return -2;
+                       return 0;
                }
 
                if (c == '!') {
-                       /* Check the extention */
+                       /* Check the extension */
                        gif_set_get_extension (context);
-                       continue;
+                       return 0;
                }
 
                /* look for frame */
@@ -815,13 +1337,15 @@ gif_get_next_step (GifContext *context)
                        /* Not a valid start character */
                        continue;
                }
-               /* assume it's frame info */
+               /* load the frame */
                gif_set_get_frame_info (context);
                return 0;
        }
 }
 
 
+#define LOG(x) /* g_print ("%s: %s\n", G_STRLOC, x); */
+
 static gint
 gif_main_loop (GifContext *context)
 {
@@ -830,48 +1354,63 @@ gif_main_loop (GifContext *context)
        do {
                switch (context->state) {
                case GIF_START:
+                        LOG("start\n");
                        retval = gif_init (context);
                        break;
 
                case GIF_GET_COLORMAP:
+                        LOG("get_colormap\n");
                        retval = gif_get_colormap (context);
                        if (retval == 0)
                                context->state = GIF_GET_NEXT_STEP;
                        break;
 
                case GIF_GET_NEXT_STEP:
+                        LOG("next_step\n");
                        retval = gif_get_next_step (context);
                        break;
 
                case GIF_GET_FRAME_INFO:
+                        LOG("frame_info\n");
                        retval = gif_get_frame_info (context);
                        break;
 
-               case GIF_GET_EXTENTION:
+               case GIF_GET_EXTENSION:
+                        LOG("get_extension\n");
                        retval = gif_get_extension (context);
                        if (retval == 0)
                                context->state = GIF_GET_NEXT_STEP;
                        break;
 
                case GIF_GET_COLORMAP2:
-                       retval = gif_get_colormap (context);
+                        LOG("get_colormap2\n");
+                       retval = gif_get_colormap2 (context);
                        if (retval == 0)
                                gif_set_prepare_lzw (context);
                        break;
 
                case GIF_PREPARE_LZW:
+                        LOG("prepare_lzw\n");
                        retval = gif_prepare_lzw (context);
                        break;
 
                case GIF_LZW_FILL_BUFFER:
+                        LOG("fill_buffer\n");
                        retval = gif_lzw_fill_buffer (context);
                        break;
-                       
+
+               case GIF_LZW_CLEAR_CODE:
+                        LOG("clear_code\n");
+                       retval = gif_lzw_clear_code (context);
+                       break;
+
                case GIF_GET_LZW:
+                        LOG("get_lzw\n");
                        retval = gif_get_lzw (context);
                        break;
 
                case GIF_DONE:
+                        LOG("done\n");
                default:
                        retval = 0;
                        goto done;
@@ -881,64 +1420,148 @@ gif_main_loop (GifContext *context)
        return retval;
 }
 
-/* Shared library entry point */
-GdkPixbuf *
-image_load (FILE *file)
+static GifContext *
+new_context (void)
 {
        GifContext *context;
 
-       g_return_val_if_fail (file != NULL, NULL);
+       context = g_try_malloc (sizeof (GifContext));
+        if (context == NULL)
+                return NULL;
 
-       context = g_new (GifContext, 1);
-       context->file = file;
-       context->pixbuf = NULL;
+        memset (context, 0, sizeof (GifContext));
+        
+        context->animation = g_object_new (GDK_TYPE_PIXBUF_GIF_ANIM, NULL);
+       context->frame = NULL;
+       context->file = NULL;
        context->state = GIF_START;
-       context->func = NULL;
+       context->prepare_func = NULL;
+       context->update_func = NULL;
+       context->user_data = NULL;
+       context->buf = NULL;
+       context->amount_needed = 0;
+       context->gif89.transparent = -1;
+       context->gif89.delay_time = -1;
+       context->gif89.input_flag = -1;
+       context->gif89.disposal = -1;
+        context->animation->loop = 1;
+        context->in_loop_extension = FALSE;
+        context->stop_after_first_frame = FALSE;
+
+       return context;
+}
+/* Shared library entry point */
+static GdkPixbuf *
+gdk_pixbuf__gif_image_load (FILE *file, GError **error)
+{
+       GifContext *context;
+       GdkPixbuf *pixbuf;
 
-       gif_main_loop (context);
+       g_return_val_if_fail (file != NULL, NULL);
 
-       return context->pixbuf;
+       context = new_context ();
+
+        if (context == NULL) {
+                g_set_error_literal (error,
+                                     GDK_PIXBUF_ERROR,
+                                     GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
+                                     _("Not enough memory to load GIF file"));
+                return NULL;
+        }
+        
+       context->file = file;
+        context->error = error;
+        context->stop_after_first_frame = TRUE;
+
+       if (gif_main_loop (context) == -1 || context->animation->frames == NULL) {
+                if (context->error && *(context->error) == NULL)
+                        g_set_error_literal (context->error,
+                                             GDK_PIXBUF_ERROR,
+                                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                             _("GIF file was missing some data (perhaps it was truncated somehow?)"));
+        }
+        
+        pixbuf = gdk_pixbuf_animation_get_static_image (GDK_PIXBUF_ANIMATION (context->animation));
+
+        if (pixbuf)
+                g_object_ref (pixbuf);
+
+        g_object_unref (context->animation);
+        
+        g_free (context->buf);
+       g_free (context);
+       return pixbuf;
 }
 
-gpointer
-image_begin_load (ModulePreparedNotifyFunc func, gpointer user_data)
+static gpointer
+gdk_pixbuf__gif_image_begin_load (GdkPixbufModuleSizeFunc size_func,
+                                  GdkPixbufModulePreparedFunc prepare_func,
+                                 GdkPixbufModuleUpdatedFunc update_func,
+                                 gpointer user_data,
+                                  GError **error)
 {
        GifContext *context;
 
+#ifdef IO_GIFDEBUG
        count = 0;
-       context = g_new (GifContext, 1);
-       context->func = func;
+#endif
+       context = new_context ();
+
+        if (context == NULL) {
+                g_set_error_literal (error,
+                                     GDK_PIXBUF_ERROR,
+                                     GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
+                                     _("Not enough memory to load GIF file"));
+                return NULL;
+        }
+        
+        context->error = error;
+       context->prepare_func = prepare_func;
+       context->update_func = update_func;
        context->user_data = user_data;
-       context->file = NULL;
-       context->pixbuf = NULL;
-       context->state = GIF_START;
-       context->buf = NULL;
-       context->amount_needed = 0;
+
        return (gpointer) context;
 }
 
-void
-image_stop_load (gpointer data)
+static gboolean
+gdk_pixbuf__gif_image_stop_load (gpointer data, GError **error)
 {
        GifContext *context = (GifContext *) data;
-
-       if (context->pixbuf)
-               gdk_pixbuf_unref (context->pixbuf);
-//     g_free (context->buf);
+        gboolean retval = TRUE;
+        
+        if (context->state != GIF_DONE || context->animation->frames == NULL) {
+                g_set_error_literal (error,
+                                     GDK_PIXBUF_ERROR,
+                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                     _("GIF image was truncated or incomplete."));
+
+                retval = FALSE;
+        }
+        
+        g_object_unref (context->animation);
+
+       g_free (context->buf);
        g_free (context);
+
+        return retval;
 }
 
-gboolean
-image_load_increment (gpointer data, guchar *buf, guint size)
+static gboolean
+gdk_pixbuf__gif_image_load_increment (gpointer data,
+                                      const guchar *buf, guint size,
+                                      GError **error)
 {
        gint retval;
        GifContext *context = (GifContext *) data;
 
+        context->error = error;
+        
        if (context->amount_needed == 0) {
                /* we aren't looking for some bytes. */
                /* we can use buf now, but we don't want to keep it around at all.
                 * it will be gone by the end of the call. */
-               context->buf = buf;
+               context->buf = (guchar*) buf; /* very dubious const cast */
                context->ptr = 0;
                context->size = size;
        } else {
@@ -961,19 +1584,22 @@ image_load_increment (gpointer data, guchar *buf, guint size)
 
        retval = gif_main_loop (context);
 
-       if (retval == -2)
+       if (retval == -2) {
+               if (context->buf == buf)
+                        context->buf = NULL;
                return FALSE;
+        }
        if (retval == -1) {
                /* we didn't have enough memory */
                /* prepare for the next image_load_increment */
                if (context->buf == buf) {
                        g_assert (context->size == size);
-                       context->buf = (guchar *)g_new (guchar, context->amount_needed + (context->size - context->ptr));
+                       context->buf = g_new (guchar, context->amount_needed + (context->size - context->ptr));
                        memcpy (context->buf, buf + context->ptr, context->size - context->ptr);
                } else {
                        /* copy the left overs to the begining of the buffer */
                        /* and realloc the memory */
-                       memcpy (context->buf, context->buf, context->size - context->ptr);
+                       memmove (context->buf, context->buf + context->ptr, context->size - context->ptr);
                        context->buf = g_realloc (context->buf, context->amount_needed + (context->size - context->ptr));
                }
                context->size = context->size - context->ptr;
@@ -985,3 +1611,88 @@ image_load_increment (gpointer data, guchar *buf, guint size)
        }
        return TRUE;
 }
+
+static GdkPixbufAnimation *
+gdk_pixbuf__gif_image_load_animation (FILE *file,
+                                      GError **error)
+{
+       GifContext *context;
+       GdkPixbufAnimation *animation;
+
+       g_return_val_if_fail (file != NULL, NULL);
+
+       context = new_context ();
+
+        if (context == NULL) {
+                g_set_error_literal (error,
+                                     GDK_PIXBUF_ERROR,
+                                     GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
+                                     _("Not enough memory to load GIF file"));
+                return NULL;
+        }
+        
+        context->error = error;
+       context->file = file;
+
+       if (gif_main_loop (context) == -1 || context->animation->frames == NULL) {
+                if (context->error && *(context->error) == NULL)
+                        g_set_error_literal (context->error,
+                                             GDK_PIXBUF_ERROR,
+                                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                             _("GIF file was missing some data (perhaps it was truncated somehow?)"));
+
+                g_object_unref (context->animation);
+                context->animation = NULL;
+        }
+
+        if (context->animation)
+                animation = GDK_PIXBUF_ANIMATION (context->animation);
+        else
+                animation = NULL;
+
+        if (context->error && *(context->error))
+                g_print ("%s\n", (*(context->error))->message);
+        
+        g_free (context->buf);
+       g_free (context);
+       return animation;
+}
+
+#ifndef INCLUDE_gif
+#define MODULE_ENTRY(function) G_MODULE_EXPORT void function
+#else
+#define MODULE_ENTRY(function) void _gdk_pixbuf__gif_ ## function
+#endif
+
+MODULE_ENTRY (fill_vtable) (GdkPixbufModule *module)
+{
+        module->load = gdk_pixbuf__gif_image_load;
+        module->begin_load = gdk_pixbuf__gif_image_begin_load;
+        module->stop_load = gdk_pixbuf__gif_image_stop_load;
+        module->load_increment = gdk_pixbuf__gif_image_load_increment;
+        module->load_animation = gdk_pixbuf__gif_image_load_animation;
+}
+
+MODULE_ENTRY (fill_info) (GdkPixbufFormat *info)
+{
+        static GdkPixbufModulePattern signature[] = {
+                { "GIF8", NULL, 100 },
+                { NULL, NULL, 0 }
+        };
+       static gchar * mime_types[] = {
+               "image/gif",
+               NULL
+       };
+       static gchar * extensions[] = {
+               "gif",
+               NULL
+       };
+
+       info->name = "gif";
+        info->signature = signature;
+       info->description = N_("The GIF image format");
+       info->mime_types = mime_types;
+       info->extensions = extensions;
+       info->flags = GDK_PIXBUF_FORMAT_THREADSAFE;
+       info->license = "LGPL";
+}