Add PluginManager class for client plugin support

meson.build

@@ -46,6 +46,7 @@ vapi_dir = join_paths(meson.source_root(), 'bindings', 'vapi')
 metadata_dir = join_paths(meson.source_root(), 'bindings', 'metadata')
 dbus_services_dir = join_paths(datadir, 'dbus-1', 'services')
 web_extensions_dir = join_paths(libdir, 'geary', 'web-extensions')
+plugins_dir = join_paths(libdir, 'geary', 'plugins')
 
 # Make sure Meson can find our custom VAPI's
 add_project_arguments([
@@ -201,6 +202,7 @@ conf.set_quoted('_SOURCE_ROOT_DIR', meson.source_root())
 conf.set_quoted('_GSETTINGS_DIR', join_paths(meson.build_root(), 'desktop'))
 conf.set_quoted('_INSTALL_PREFIX', geary_prefix)
 conf.set_quoted('_WEB_EXTENSIONS_DIR', web_extensions_dir)
+conf.set_quoted('_PLUGINS_DIR', plugins_dir)
 conf.set_quoted('LANGUAGE_SUPPORT_DIRECTORY', locale_dir)
 conf.set_quoted('ISO_CODE_639_XML', iso_639_xml)
 conf.set_quoted('ISO_CODE_3166_XML', iso_3166_xml)

po/POTFILES.in

@@ -20,6 +20,7 @@ src/client/application/application-command.vala
 src/client/application/application-contact-store.vala
 src/client/application/application-contact.vala
 src/client/application/application-controller.vala
+src/client/application/application-plugin-manager.vala
 src/client/application/application-startup-manager.vala
 src/client/application/geary-application.vala
 src/client/application/goa-mediator.vala

src/client/application/application-controller.vala

@@ -152,6 +152,8 @@ public class Application.Controller : Geary.BaseObject {
     private NewMessagesIndicator new_messages_indicator;
     private UnityLauncher unity_launcher;
 
+    private PluginManager plugin_manager;
+
     // Null if none selected
     private Geary.Folder? current_folder = null;
 
@@ -271,6 +273,10 @@ public class Application.Controller : Geary.BaseObject {
 
         }
 
+        this.plugin_manager = new PluginManager(
+            application.get_app_plugins_dir()
+        );
+
         // Create the main window (must be done after creating actions.)
         main_window = new MainWindow(this.application);
         main_window.retry_service_problem.connect(on_retry_service_problem);

src/client/application/application-plugin-manager.vala

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2019 Michael Gratton <mike@vee.net>
+ *
+ * This software is licensed under the GNU Lesser General Public License
+ * (version 2.1 or later). See the COPYING file in this distribution.
+ */
+
+/*
+ * Finds and manages application plugins.
+ */
+public class Application.PluginManager : GLib.Object {
+
+
+    private Peas.Engine engine;
+
+
+    public PluginManager(GLib.File app_plugin_dir) {
+        this.engine = Peas.Engine.get_default();
+        this.engine.add_search_path(app_plugin_dir.get_path(), null);
+
+        // Load built-in plugins
+        foreach (Peas.PluginInfo info in this.engine.get_plugin_list()) {
+            if (info.is_builtin()) {
+                this.engine.load_plugin(info);
+            }
+        }
+    }
+
+}

src/client/application/geary-application.vala

@@ -10,6 +10,7 @@
 extern const string _INSTALL_PREFIX;
 extern const string _GSETTINGS_DIR;
 extern const string _WEB_EXTENSIONS_DIR;
+extern const string _PLUGINS_DIR;
 extern const string _SOURCE_ROOT_DIR;
 extern const string _BUILD_ROOT_DIR;
 extern const string GETTEXT_PACKAGE;
@@ -614,6 +615,19 @@ public class GearyApplication : Gtk.Application {
             : GLib.File.new_for_path(BUILD_ROOT_DIR).get_child("src");
     }
 
+    /**
+     * Returns the directory containing the application's plugins.
+     *
+     * When running from the installation prefix, this will be based
+     * on the Meson `libdir` option, and can be set by invoking `meson
+     * configure` as appropriate.
+     */
+    public GLib.File get_app_plugins_dir() {
+        return (is_installed)
+            ? GLib.File.new_for_path(_PLUGINS_DIR)
+            : GLib.File.new_for_path(BUILD_ROOT_DIR).get_child("src");
+    }
+
     /** Displays a URI on the current active window, if any. */
     public void show_uri(string uri) throws Error {
         bool success = Gtk.show_uri_on_window(

src/client/meson.build

@@ -6,6 +6,7 @@ geary_client_vala_sources = files(
   'application/application-contact-store.vala',
   'application/application-contact.vala',
   'application/application-controller.vala',
+  'application/application-plugin-manager.vala',
   'application/application-startup-manager.vala',
   'application/geary-application.vala',
   'application/geary-config.vala',