bbhtt · Sep 15, 2026 · Sep 15, 2026 · Sep 15, 2026 · Sep 15, 2026
diff --git a/.gitignore b/.gitignore
@@ -104,3 +104,4 @@ system-helper/org.freedesktop.Flatpak.rules
 flatpak-bwrap
 py-compile
 libglnx-config.h
+subprojects/.wraplock
diff --git a/doc/flatpak-builder.xml b/doc/flatpak-builder.xml
@@ -624,6 +624,18 @@
                 </para></listitem>
             </varlistentry>
 
+            <varlistentry>
+                <term><option>--compose-image-format=FORMAT</option></term>
+
+                <listitem><para>
+                  Set the AppStream compose image format used for
+                  generated icons and screenshots. Accepted values
+                  are <literal>png</literal> and <literal>jxl</literal>.
+                  <literal>jxl</literal> requires AppStream version >= 1.2.0.
+                  Defaults to <literal>png</literal> if unspecified.
+                </para></listitem>
+            </varlistentry>
+
             <varlistentry>
                 <term><option>--add-tag=TAG</option></term>
 

diff --git a/src/builder-context.c b/src/builder-context.c
@@ -90,6 +90,7 @@ struct BuilderContext
   BuilderSdkConfig *sdk_config;
 
   BuilderAsUrlPolicy as_url_policy;
+  BuilderAsImageFormat as_image_format;
 };
 
 typedef struct
@@ -1257,6 +1258,19 @@ builder_context_get_as_url_policy (BuilderContext *self)
   return self->as_url_policy;
 }
 
+void
+builder_context_set_as_image_format (BuilderContext       *self,
+                                     BuilderAsImageFormat  format)
+{
+  self->as_image_format = format;
+}
+
+BuilderAsImageFormat
+builder_context_get_as_image_format (BuilderContext *self)
+{
+  return self->as_image_format;
+}
+
 gboolean
 builder_context_resolve_source_uri (BuilderContext *self,
                                     const char     *url,

diff --git a/src/builder-context.h b/src/builder-context.h
@@ -34,6 +34,11 @@ typedef enum {
   BUILDER_AS_URL_POLICY_FULL,
 } BuilderAsUrlPolicy;
 
+typedef enum {
+  BUILDER_AS_IMAGE_FORMAT_PNG = 0,
+  BUILDER_AS_IMAGE_FORMAT_JXL,
+} BuilderAsImageFormat;
+
 /* Same as SOUP_HTTP_URI_FLAGS, means all possible flags for http uris */
 
 #if GLIB_CHECK_VERSION (2, 68, 0)
@@ -202,6 +207,10 @@ void             builder_context_set_as_url_policy (BuilderContext      *self,
                                                     BuilderAsUrlPolicy  policy);
 BuilderAsUrlPolicy builder_context_get_as_url_policy (BuilderContext   *self);
 
+void             builder_context_set_as_image_format (BuilderContext       *self,
+                                                      BuilderAsImageFormat  format);
+BuilderAsImageFormat builder_context_get_as_image_format (BuilderContext   *self);
+
 G_DEFINE_AUTOPTR_CLEANUP_FUNC (BuilderContext, g_object_unref)
 
 G_END_DECLS

diff --git a/src/builder-main.c b/src/builder-main.c
@@ -90,6 +90,7 @@ static gboolean opt_log_system_bus;
 static gboolean opt_yes;
 static gint64 opt_source_date_epoch = -1;
 static gchar *opt_as_url_policy = NULL;
+static gchar *opt_as_image_format = NULL;
 
 static GOptionEntry entries[] = {
   { "verbose", 'v', 0, G_OPTION_ARG_NONE, &opt_verbose, "Print debug information during command processing", NULL },
@@ -146,6 +147,7 @@ static GOptionEntry entries[] = {
   { "no-shallow-clone", 0, 0, G_OPTION_ARG_NONE, &opt_no_shallow_clone, "Don't use shallow clones when mirroring git repos", NULL },
   { "override-source-date-epoch", 0, 0, G_OPTION_ARG_INT64, &opt_source_date_epoch, "Use this timestamp to perform the build, instead of the last modification time of the manifest.", NULL },
   { "compose-url-policy", 0, 0, G_OPTION_ARG_STRING, &opt_as_url_policy, "Set the AppStream compose URL policy to either 'partial' (default) or 'full'", "POLICY" },
+  { "compose-image-format", 0, 0, G_OPTION_ARG_STRING, &opt_as_image_format, "Set the AppStream compose image format to either 'png' (default) or 'jxl'", "FORMAT" },
   { NULL }
 };
 
@@ -636,6 +638,28 @@ main (int    argc,
       builder_context_set_as_url_policy (build_context, policy);
     }
 
+    {
+      BuilderAsImageFormat image_format = BUILDER_AS_IMAGE_FORMAT_PNG;
+
+      if (opt_as_image_format == NULL || g_strcmp0 (opt_as_image_format, "png") == 0)
+        image_format = BUILDER_AS_IMAGE_FORMAT_PNG;
+      else if (g_strcmp0 (opt_as_image_format, "jxl") == 0)
+        image_format = BUILDER_AS_IMAGE_FORMAT_JXL;
+      else
+        {
+          g_printerr ("Invalid value for --compose-image-format: %s\n", opt_as_image_format);
+          return 1;
+        }
+
+      if (image_format == BUILDER_AS_IMAGE_FORMAT_JXL && !appstream_has_version (1, 2, 0))
+        {
+          g_printerr ("AppStream version >= 1.2.0 required for 'jxl' compose image format\n");
+          return 1;
+        }
+
+      builder_context_set_as_image_format (build_context, image_format);
+    }
+
   git_init_email ();
 
   if (!builder_context_create_state_dir (build_context, &error))

diff --git a/src/builder-manifest.c b/src/builder-manifest.c
@@ -2428,6 +2428,7 @@ cmpstringp (const void *p1, const void *p2)
 static gboolean
 appstreamcli_compose (GError             **error,
                       BuilderAsUrlPolicy   as_url_policy,
+                      BuilderAsImageFormat as_image_format,
                       ...)
 {
   g_autoptr(GPtrArray) args = NULL;
@@ -2441,7 +2442,22 @@ appstreamcli_compose (GError             **error,
   if (as_url_policy == BUILDER_AS_URL_POLICY_FULL)
     g_ptr_array_add (args, g_strdup ("--no-partial-urls"));
 
-  va_start (ap, as_url_policy);
+  /* For AppStream >= 1.2.0 we need to explicitly pass --image-format,
+     since JXL is now the default and we want to keep producing
+     PNG unless the user asked for JXL. */
+  if (appstream_has_version (1, 2, 0))
+    {
+      g_ptr_array_add (args, g_strdup ("--image-format"));
+      g_ptr_array_add (args, g_strdup (as_image_format == BUILDER_AS_IMAGE_FORMAT_JXL ? "jxl" : "png"));
+    }
+  else
+    {
+      /* For AppStream < 1.2.0, --image-format doesn't exist and PNG is
+         the only supported format. The JXL choice is gated in main
+         on having >= 1.2.0 */
+    }
+
+  va_start (ap, as_image_format);
   while ((arg = va_arg (ap, const gchar *)))
     g_ptr_array_add (args, g_strdup (arg));
   g_ptr_array_add (args, NULL);
@@ -3092,6 +3108,7 @@ builder_manifest_cleanup (BuilderManifest *self,
           const char *opt_mirror_screenshots_url = builder_context_get_opt_mirror_screenshots_url (context);
           gboolean opt_export_only = builder_context_get_opt_export_only (context);
           BuilderAsUrlPolicy as_url_policy = builder_context_get_as_url_policy (context);
+          BuilderAsImageFormat as_image_format = builder_context_get_as_image_format (context);
 
           if (opt_mirror_screenshots_url && !opt_export_only)
             {
@@ -3104,6 +3121,7 @@ builder_manifest_cleanup (BuilderManifest *self,
               g_print ("Saving screenshots in %s\n", flatpak_file_get_path_cached (media_dir));
               if (!appstreamcli_compose (error,
                                          as_url_policy,
+                                         as_image_format,
                                          "--prefix=/",
                                          origin,
                                          arg_base_url,
@@ -3121,6 +3139,7 @@ builder_manifest_cleanup (BuilderManifest *self,
               g_print ("Running appstreamcli compose\n");
               if (!appstreamcli_compose (error,
                                          as_url_policy,
+                                         as_image_format,
                                          "--prefix=/",
                                          origin,
                                          result_root_arg,

diff --git a/tests/Makefile.am.inc b/tests/Makefile.am.inc
@@ -91,6 +91,7 @@ dist_test_scripts = \
 	tests/test-builder-licence-paths.sh \
 	tests/test-builder-locale-migration.sh \
 	tests/test-sandboxed-mode-source-resolution.sh \
+	tests/test-appstream.sh \
 	$(NULL)
 
 @VALGRIND_CHECK_RULES@

diff --git a/tests/meson.build b/tests/meson.build
@@ -15,6 +15,7 @@ test_names = [
   'test-builder-licence-paths',
   'test-builder-locale-migration',
   'test-sandboxed-mode-source-resolution',
+  'test-appstream',
 ]
 
 tap_test = find_program(

diff --git a/tests/test-appstream.sh b/tests/test-appstream.sh
@@ -0,0 +1,84 @@
+#!/bin/bash
+#
+# Copyright (C) 2026 Boudhayan Bhattacharya <bbhtt@bbhtt.in>
+#
+# 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, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+set -euo pipefail
+
+. $(dirname $0)/libtest.sh
+
+skip_without_fuse
+
+echo "1..3"
+
+setup_repo
+install_repo
+setup_sdk_repo
+install_sdk_repo
+
+cd $TEST_DATA_DIR/
+
+cp $(dirname $0)/org.flatpak_builder.gui.desktop .
+cp $(dirname $0)/org.flatpak_builder.gui.metainfo.xml .
+cp $(dirname $0)/org.test.Hello-256.png .
+cp $(dirname $0)/org.flatpak.appstream_media.json .
+
+# test compose partial url policy
+APPDIR=builddir_sc \
+run_build \
+    --mirror-screenshots-url=https://example.org/media \
+    --state-dir .fp-compose-url-policy-partial \
+    --compose-url-policy=partial \
+    org.flatpak.appstream_media.json
+# we test for the icon tag instead of screenshot
+# the former works offline the latter does not
+gzip -cdq builddir_sc/files/share/app-info/xmls/org.flatpak.appstream_media.xml.gz|grep -Eq '>org/flatpak/appstream_media/[^/]+/icons/128x128/org.flatpak.appstream_media.png</icon>'
+
+echo "ok compose partial url policy"
+
+# test compose full url policy
+if appstream_has_version 0 16 3; then
+    APPDIR=builddir_sc \
+    run_build \
+        --mirror-screenshots-url=https://example.org/media \
+        --state-dir .fp-compose-url-policy-full \
+        --compose-url-policy=full \
+        org.flatpak.appstream_media.json
+
+    gzip -cdq builddir_sc/files/share/app-info/xmls/org.flatpak.appstream_media.xml.gz|grep -Eq '>https://example.org/media/org/flatpak/appstream_media/[^/]+/icons/128x128/org.flatpak.appstream_media.png</icon>'
+
+    echo "ok compose full url policy"
+else
+    echo "ok # Skip AppStream < 0.16.3"
+fi
+
+# test compose jxl image format
+if appstream_has_version 1 2 0; then
+    APPDIR=builddir_jxl \
+    run_build \
+        --mirror-screenshots-url=https://example.org/media \
+        --state-dir .fp-compose-image-format-jxl \
+        --compose-url-policy=full \
+        --compose-image-format=jxl \
+        org.flatpak.appstream_media.json
+
+        gzip -cdq builddir_jxl/files/share/app-info/xmls/org.flatpak.appstream_media.xml.gz|grep -Eq '>https://example.org/media/org/flatpak/appstream_media/[^/]+/icons/128x128/org.flatpak.appstream_media.jxl</icon>'
+
+    echo "ok compose jxl image format"
+else
+    echo "ok # Skip AppStream < 1.2.0"
+fi
diff --git a/tests/test-builder.sh b/tests/test-builder.sh
@@ -23,7 +23,7 @@ set -euo pipefail
 
 skip_without_fuse
 
-echo "1..12"
+echo "1..10"
 
 setup_repo
 install_repo
@@ -49,12 +49,8 @@ cp $(dirname $0)/Hello-desktop.appdata.xml .
 cp $(dirname $0)/org.test.Hello.desktop .
 cp $(dirname $0)/org.test.Hello.xml .
 cp $(dirname $0)/org.test.Hello.appdata.xml .
-cp $(dirname $0)/org.flatpak_builder.gui.desktop .
 cp $(dirname $0)/org.flatpak_builder.gui.json .
-cp $(dirname $0)/org.flatpak_builder.gui.metainfo.xml .
 cp $(dirname $0)/org.test.Hello.png .
-cp $(dirname $0)/org.test.Hello-256.png .
-cp $(dirname $0)/org.flatpak.appstream_media.json .
 cp $(dirname $0)/org.flatpak.install_test.json .
 cp $(dirname $0)/test-locale-cleanup.json .
 mkdir include1
@@ -150,35 +146,6 @@ find outdir_sc -path "*/icons/64x64/org.test.Hello.png" -type f | grep -q .
 
 echo "ok screenshot ref commit"
 
-# test compose partial url policy
-APPDIR=builddir_sc \
-run_build \
-    --mirror-screenshots-url=https://example.org/media \
-    --state-dir .fp-compose-url-policy-partial \
-    --compose-url-policy=partial \
-    org.flatpak.appstream_media.json
-# we test for the icon tag instead of screenshot
-# the former works offline the latter does not
-gzip -cdq builddir_sc/files/share/app-info/xmls/org.flatpak.appstream_media.xml.gz|grep -Eq '>org/flatpak/appstream_media/[^/]+/icons/128x128/org.flatpak.appstream_media.png</icon>'
-
-echo "ok compose partial url policy"
-
-# test compose full url policy
-if appstream_has_version 0 16 3; then
-    APPDIR=builddir_sc \
-    run_build \
-        --mirror-screenshots-url=https://example.org/media \
-        --state-dir .fp-compose-url-policy-full \
-        --compose-url-policy=full \
-        org.flatpak.appstream_media.json
-
-    gzip -cdq builddir_sc/files/share/app-info/xmls/org.flatpak.appstream_media.xml.gz|grep -Eq '>https://example.org/media/org/flatpak/appstream_media/[^/]+/icons/128x128/org.flatpak.appstream_media.png</icon>'
-
-    echo "ok compose full url policy"
-else
-    echo "ok # Skip AppStream < 0.16.3"
-fi
-
 # test install
 APPDIR=builddir run_build --user --install org.flatpak.install_test.json