fix(linux): set GTK window icon from bundled app icon

apps/app_seeds/linux/runner/my_application.cc

@@ -19,6 +19,24 @@ static void first_frame_cb(MyApplication* self, FlView* view) {
   gtk_widget_show(gtk_widget_get_toplevel(GTK_WIDGET(view)));
 }
 
+// GTK does not pick up an icon from the Flutter bundle; load the packaged app
+// icon so the window/taskbar shows it (X11; on Wayland the icon comes from an
+// installed .desktop file matching APPLICATION_ID).
+static void set_window_icon(GtkWindow* window) {
+  g_autofree gchar* exe_path = g_file_read_link("/proc/self/exe", nullptr);
+  if (exe_path == nullptr) {
+    return;
+  }
+  g_autofree gchar* exe_dir = g_path_get_dirname(exe_path);
+  g_autofree gchar* icon_path = g_build_filename(
+      exe_dir, "data", "flutter_assets", "assets", "icon.png", nullptr);
+  g_autoptr(GError) error = nullptr;
+  if (!gtk_window_set_icon_from_file(window, icon_path, &error)) {
+    g_warning("Failed to set window icon from %s: %s", icon_path,
+              error->message);
+  }
+}
+
 // Implements GApplication::activate.
 static void my_application_activate(GApplication* application) {
   MyApplication* self = MY_APPLICATION(application);
@@ -53,6 +71,7 @@ static void my_application_activate(GApplication* application) {
   }
 
   gtk_window_set_default_size(window, 1280, 720);
+  set_window_icon(window);
 
   g_autoptr(FlDartProject) project = fl_dart_project_new();
   fl_dart_project_set_dart_entrypoint_arguments(

apps/app_seeds/pubspec.yaml

@@ -98,6 +98,8 @@ flutter:
   assets:
     - assets/catalog/species.json
     - assets/logo.png
+    # Bundled so the Linux runner can use it as the GTK window icon.
+    - assets/icon.png
   fonts:
     # Custom seed-themed icon glyphs (chars a–k). See docs/mockups/seedks-glyphs.png.
     - family: seedks