Add code to load jpegs

This lets us avoid gdk-pixbuf for loading
textures from the common image formats.

As a consequence, we are now linking against libjpeg.

gdk/gdkjpeg.c

@@ -0,0 +1,234 @@
+/* GDK - The GIMP Drawing Kit
+ * Copyright (C) 2021 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "gdkjpeg.h"
+
+#include "gdktexture.h"
+#include "gdkmemorytextureprivate.h"
+#include <jpeglib.h>
+#include <jerror.h>
+#include <setjmp.h>
+
+/* {{{ IO handling */
+
+#define BUF_SIZE 65536
+
+typedef struct {
+  struct jpeg_source_mgr pub;
+  JOCTET buffer[BUF_SIZE];
+  long skip_next;
+  GInputStream *stream;
+} my_source_mgr;
+
+static void
+init_source (j_decompress_ptr info)
+{
+  my_source_mgr *src = (my_source_mgr *) info->src;
+  src->skip_next = 0;
+}
+
+static void
+term_source (j_decompress_ptr info)
+{
+}
+
+static boolean
+fill_input_buffer (j_decompress_ptr info)
+{
+  my_source_mgr *src = (my_source_mgr *) info->src;
+  size_t nbytes;
+
+  nbytes = g_input_stream_read (src->stream, src->buffer, BUF_SIZE, NULL, NULL);
+
+  if (nbytes <= 0)
+    {
+      /* Insert a fake EOI marker */
+      src->buffer[0] = (JOCTET) 0xFF;
+      src->buffer[1] = (JOCTET) JPEG_EOI;
+      nbytes = 2;
+    }
+
+  src->pub.next_input_byte = src->buffer;
+  src->pub.bytes_in_buffer = nbytes;
+
+  return TRUE;
+}
+
+static void
+skip_input_data (j_decompress_ptr info,
+                 long             num_bytes)
+{
+  my_source_mgr *src = (my_source_mgr *) info->src;
+
+  if (num_bytes > 0)
+    {
+      while (num_bytes > src->pub.bytes_in_buffer)
+        {
+          num_bytes -= src->pub.bytes_in_buffer;
+          fill_input_buffer (info);
+        }
+
+      src->pub.next_input_byte += num_bytes;
+      src->pub.bytes_in_buffer -= num_bytes;
+    }
+}
+
+/* }}} */
+/* {{{ Error handling */
+
+struct error_handler_data {
+        struct jpeg_error_mgr pub;
+        sigjmp_buf setjmp_buffer;
+        GError **error;
+};
+
+static void
+fatal_error_handler (j_common_ptr cinfo)
+{
+  struct error_handler_data *errmgr;
+
+  errmgr = (struct error_handler_data *) cinfo->err;
+
+  siglongjmp (errmgr->setjmp_buffer, 1);
+
+  g_assert_not_reached ();
+}
+
+static void
+output_message_handler (j_common_ptr cinfo)
+{
+  /* do nothing */
+}
+
+/* }}} */
+ /* {{{ Public API */
+
+GdkTexture *
+gdk_load_jpeg (GInputStream  *stream,
+               GError       **error)
+{
+  struct jpeg_decompress_struct info;
+  struct error_handler_data jerr;
+  struct jpeg_error_mgr err;
+  my_source_mgr src;
+  int width, height;
+  int size;
+  unsigned char *data;
+  unsigned char *row[1];
+  GBytes *bytes;
+  GdkTexture *texture;
+
+  info.err = jpeg_std_error (&jerr.pub);
+  jerr.pub.error_exit = fatal_error_handler;
+  jerr.pub.output_message = output_message_handler;
+  jerr.error = error;
+
+  if (sigsetjmp (jerr.setjmp_buffer, 1))
+    {
+      jpeg_destroy_decompress (&info);
+      return NULL;
+    }
+
+  info.err = jpeg_std_error (&err);
+  jpeg_create_decompress (&info);
+
+  src.pub.init_source = init_source;
+  src.pub.fill_input_buffer = fill_input_buffer;
+  src.pub.skip_input_data = skip_input_data;
+  src.pub.resync_to_restart = jpeg_resync_to_restart;
+  src.pub.term_source = term_source;
+  src.pub.bytes_in_buffer = 0;
+  src.pub.next_input_byte = NULL;
+  src.stream = stream;
+
+  info.src = (struct jpeg_source_mgr *)&src;
+
+  jpeg_read_header (&info, TRUE);
+  jpeg_start_decompress (&info);
+
+  width = info.output_width;
+  height = info.output_height;
+
+  size = width * height * 3;
+  data = g_malloc (size);
+
+  while (info.output_scanline < info.output_height)
+    {
+       row[0] = (unsigned char *)(&data[3 *info.output_width * info.output_scanline]);
+       jpeg_read_scanlines (&info, row, 1);
+    }
+
+  jpeg_finish_decompress (&info);
+  jpeg_destroy_decompress (&info);
+
+  bytes = g_bytes_new_take (data, size);
+
+  texture = gdk_memory_texture_new (width, height,
+                                    GDK_MEMORY_R8G8B8,
+                                    bytes, width * 3);
+
+  g_bytes_unref (bytes);
+
+  return texture;
+}
+
+/* }}} */
+/* {{{ Async code */
+
+static void
+load_jpeg_in_thread (GTask        *task,
+                     gpointer      source_object,
+                     gpointer      task_data,
+                     GCancellable *cancellable)
+{
+  GInputStream *stream = source_object;
+  GdkTexture *texture;
+  GError *error = NULL;
+
+  texture = gdk_load_jpeg (stream, &error);
+
+  if (texture)
+    g_task_return_pointer (task, texture, g_object_unref);
+  else
+    g_task_return_error (task, error);
+}
+
+void
+gdk_load_jpeg_async (GInputStream         *stream,
+                     GCancellable         *cancellable,
+                     GAsyncReadyCallback   callback,
+                     gpointer              user_data)
+{
+  GTask *task;
+
+  task = g_task_new (stream, cancellable, callback, user_data);
+  g_task_run_in_thread (task, load_jpeg_in_thread);
+  g_object_unref (task);
+}
+
+GdkTexture *
+gdk_load_jpeg_finish (GAsyncResult  *result,
+                      GError       **error)
+{
+  return g_task_propagate_pointer (G_TASK (result), error);
+}
+
+/* }}} */
+
+/* vim:set foldmethod=marker expandtab: */

gdk/gdkjpeg.h

@@ -0,0 +1,35 @@
+/* GDK - The GIMP Drawing Kit
+ * Copyright (C) 2021 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GDK_JPEG_H__
+#define __GDK_JPEG_H__
+
+#include "gdkmemorytexture.h"
+#include <gio/gio.h>
+
+GdkTexture *gdk_load_jpeg         (GInputStream     *stream,
+                                   GError          **error);
+
+void        gdk_load_jpeg_async   (GInputStream           *stream,
+                                   GCancellable           *cancellable,
+                                   GAsyncReadyCallback     callback,
+                                   gpointer                user_data);
+
+GdkTexture *gdk_load_jpeg_finish  (GAsyncResult           *result,
+                                   GError                **error);
+
+#endif

gdk/meson.build

@@ -52,6 +52,7 @@ gdk_public_sources = files([
   'gdkdragsurface.c',
   'gdkpng.c',
   'gdktiff.c',
+  'gdkjpeg.c',
 ])
 
 gdk_public_headers = files([
@@ -256,7 +257,7 @@ endif
 
 libgdk = static_library('gdk',
   sources: [gdk_sources, gdk_backends_gen_headers, gdkconfig],
-  dependencies: gdk_deps + [libgtk_css_dep, png_dep, tiff_dep],
+  dependencies: gdk_deps + [libgtk_css_dep, png_dep, tiff_dep, jpeg_dep],
   link_with: [libgtk_css],
   include_directories: [confinc, gdkx11_inc, wlinc],
   c_args: libgdk_c_args + common_cflags,

meson.build

@@ -392,6 +392,7 @@ pixbuf_dep     = dependency('gdk-pixbuf-2.0', version: gdk_pixbuf_req,
                             default_options: ['png=enabled', 'jpeg=enabled', 'builtin_loaders=png,jpeg', 'man=false'])
 png_dep        = dependency('libpng16')
 tiff_dep        = dependency('libtiff-4')
+jpeg_dep       = dependency('libjpeg')
 epoxy_dep      = dependency('epoxy', version: epoxy_req,
                             fallback: ['libepoxy', 'libepoxy_dep'])
 harfbuzz_dep   = dependency('harfbuzz', version: '>= 2.1.0', required: false,