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/loaders/gdkjpeg.c

@@ -0,0 +1,127 @@
+/* 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 "gdkjpegprivate.h"
+
+#include "gdktexture.h"
+#include "gdkmemorytextureprivate.h"
+#include <jpeglib.h>
+#include <jerror.h>
+#include <setjmp.h>
+
+/* {{{ Error handling */
+
+/* No sigsetjmp on Windows */
+#ifndef HAVE_SIGSETJMP
+#define sigjmp_buf jmp_buf
+#define sigsetjmp(jb, x) setjmp(jb)
+#define siglongjmp longjmp
+#endif
+
+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 (GBytes  *input_bytes,
+               GError **error)
+{
+  struct jpeg_decompress_struct info;
+  struct error_handler_data jerr;
+  struct jpeg_error_mgr err;
+  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);
+
+  jpeg_mem_src (&info,
+                g_bytes_get_data (input_bytes, NULL),
+                g_bytes_get_size (input_bytes));
+
+  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;
+}
+
+/* }}} */
+
+/* vim:set foldmethod=marker expandtab: */

gdk/loaders/gdkjpegprivate.h

@@ -0,0 +1,29 @@
+/* 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_PRIVATE_H__
+#define __GDK_JPEG_PRIVATE_H__
+
+#include "gdkmemorytexture.h"
+#include <gio/gio.h>
+
+#define JPEG_SIGNATURE "\xff\xd8"
+
+GdkTexture *gdk_load_jpeg         (GBytes           *bytes,
+                                   GError          **error);
+
+#endif

gdk/meson.build

@@ -53,6 +53,7 @@ gdk_public_sources = files([
   'gdkdragsurface.c',
   'loaders/gdkpng.c',
   'loaders/gdktiff.c',
+  'loaders/gdkjpeg.c',
 ])
 
 gdk_public_headers = files([
@@ -258,7 +259,7 @@ 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

@@ -207,6 +207,17 @@ foreach func : check_functions
   endif
 endforeach
 
+# We use links() because sigsetjmp() is often a macro hidden behind other macros
+cdata.set('HAVE_SIGSETJMP',
+  cc.links('''#define _POSIX_SOURCE
+              #include <setjmp.h>
+              int main (void) {
+                sigjmp_buf env;
+                sigsetjmp (env, 0);
+                return 0;
+              }''', name: 'sigsetjmp'),
+)
+
 # Check for __uint128_t (gcc) by checking for 128-bit division
 uint128_t_src = '''int main() {
 static __uint128_t v1 = 100;
@@ -395,6 +406,9 @@ png_dep        = dependency('libpng',
 tiff_dep       = dependency('libtiff-4',
                             fallback: ['libtiff', 'libtiff4_dep'],
                             required: true)
+jpeg_dep       = dependency('libjpeg',
+                            fallback: ['libjpeg-turbo', 'jpeg_dep'],
+                            required: true)
 
 epoxy_dep      = dependency('epoxy', version: epoxy_req,
                             fallback: ['libepoxy', 'libepoxy_dep'])