Implement 'detached' workspace context

There is always at least one workspace context which is the context
that is currently being used by the GNOME desktop. If no running realm
is associated with this context then we consider this context to be
'detached' and store it so that the next time a context is needed to
attach to a running realm, this 'detached' context will be used rather
than asking mutter to create a new fresh context.

src/shell-realm-tracker.c

@@ -175,7 +175,6 @@ request_realm_state_finish (GObject *object, GAsyncResult *result, gpointer data
 
   realm_state_process_elements (self, response);
   g_variant_unref (response);
-  subscribe_bus_signals (self);
 }
 
 static void
@@ -301,6 +300,7 @@ on_realm_manager_appeared (GDBusConnection *connection, const gchar *name, const
       g_warning("Realm tracker already has a connection in on_realm_manager_appeared()");
   }
 
+  subscribe_bus_signals (self);
   request_realm_state (self);
 }
 

src/shell-realms.c

@@ -12,6 +12,7 @@ struct _ShellRealms {
     GList *running_realms;
     ShellRealmItem *current_realm;
     ShellRealmsWindowFrames *frames;
+    MetaWorkspaceContext *detached_context;
 };
 
 G_DEFINE_TYPE (ShellRealms, shell_realms, G_TYPE_OBJECT);
@@ -111,7 +112,6 @@ shell_realms_realm_by_window (ShellRealms *realms, MetaWindow *window)
 {
   ShellRealmItem *realm = NULL;
   gchar *realm_name = realm_name_from_window_pid (realms, window);
-  // g_warning("shell_realms_realm_by_window() realm_name=%s", realm_name);
   if (realm_name && g_strcmp0 (CITADEL_REALM_TAG, realm_name)) {
     realm = shell_realms_realm_by_name (realms, realm_name);
   }
@@ -249,6 +249,7 @@ shell_realms_set_current_item (ShellRealms *realms, ShellRealmItem *item)
 
   shell_realm_item_set_current_flag (item, TRUE);
   realms->current_realm = item;
+  g_object_notify (realms, "current-realm");
 }
 
 /*
@@ -282,13 +283,16 @@ shell_realms_add_realm_item (ShellRealms *realms,
 }
 
 static void
-remove_workspace_context (ShellRealmItem *realm)
+remove_workspace_context (ShellRealms *realms, ShellRealmItem *realm)
 {
   MetaWorkspaceContext *context = shell_realm_item_get_context (realm);
   if (context) {
+    guint id = meta_workspace_context_id (context);
     shell_realm_item_set_context (realm, NULL);
     if (!meta_workspace_context_is_current (context)) {
       meta_workspace_context_remove (context);
+    } else {
+      realms->detached_context = context;
     }
   }
 }
@@ -330,6 +334,12 @@ acquire_active_workspace_context (ShellRealms *realms, ShellRealmItem *realm)
     return;
   }
 
+  if (realms->detached_context == active_context) {
+    shell_realm_item_set_context(realm, realms->detached_context);
+    realms->detached_context = NULL;
+    return;
+  }
+
   ShellRealmItem *other_realm = find_realm_with_context (realms, active_context);
 
   if (other_realm) {
@@ -365,12 +375,19 @@ acquire_workspace_context (ShellRealms *realms, ShellRealmItem *realm)
     return;
   }
 
+  if (realms->detached_context) {
+    guint id = meta_workspace_context_id(realms->detached_context);
+    shell_realm_item_set_context(realm, realms->detached_context);
+    realms->detached_context = NULL;
+    return;
+  }
+
   MetaDisplay *display = shell_global_get_display(shell_global_get());
   MetaWorkspaceManager *workspace_manager = meta_display_get_workspace_manager(display);
   MetaWorkspaceContext *context = meta_workspace_context_new(workspace_manager);
+  guint id = meta_workspace_context_id(context);
 
   shell_realm_item_set_context(realm, context);
-
 }
 
 void
@@ -387,6 +404,8 @@ shell_realms_process_list_realm (ShellRealms *realms,
   }
 
   ShellRealmItem *item = shell_realms_add_realm_item (realms, realm_name, description, namespace, status);
+  gboolean running = shell_realm_item_is_running(item);
+  gboolean current = shell_realm_item_is_current(item);
 
   shell_realms_update_running_list_for_item (realms, item);
   shell_realm_item_set_tagged (item, TRUE);
@@ -399,7 +418,7 @@ shell_realms_process_list_realm (ShellRealms *realms,
   }
 
   if (!shell_realm_item_is_running (item) && shell_realm_item_get_context (item) != NULL) {
-    remove_workspace_context (item);
+    remove_workspace_context (realms, item);
   }
 }
 
@@ -434,7 +453,7 @@ shell_realms_remove_untagged (ShellRealms *realms)
     ShellRealmItem *item = value;
     if (!shell_realm_item_is_tagged (item)) {
       shell_realms_remove_running_realm (realms, item);
-      remove_workspace_context (item);
+      remove_workspace_context (realms, item);
       g_hash_table_iter_remove (&iter);
     }
   }
@@ -478,12 +497,29 @@ activate_workspace_context (ShellRealmItem *realm)
 void
 shell_realms_on_realm_current (ShellRealms *realms, const gchar *realm_name)
 {
+  if (strlen(realm_name) == 0) {
+    g_warning("on_realm_current(NULL)");
+    if(realms->current_realm) {
+      shell_realm_item_set_current_flag (realms->current_realm, FALSE);
+      realms->current_realm = NULL;
+    }
+    return;
+  }
+
   ShellRealmItem *item = shell_realms_realm_by_name (realms, realm_name);
 
   if (item && realms->current_realm != item) {
     shell_realms_set_current_item (realms, item);
     shell_realms_update_running_list_for_item (realms, item);
+
     activate_workspace_context (item);
+
+    // If we really did switch to another context and we have a detached context saved, then
+    // now it can be removed which will move any windows on the detached context to the newly switched context.
+    if (realms->detached_context && shell_realm_item_get_context(item) != NULL) {
+      meta_workspace_context_remove(realms->detached_context);
+      realms->detached_context = NULL;
+    }
     g_signal_emit (realms, shell_realms_signals[REALM_CONTEXT_SWITCHED], 0);
   }
 }
@@ -494,7 +530,7 @@ shell_realms_on_realm_stopped (ShellRealms *realms, const gchar *realm_name)
   ShellRealmItem *item = shell_realms_realm_by_name (realms, realm_name);
   if (item) {
     shell_realm_item_set_running_flag (item, FALSE);
-    remove_workspace_context (item);
+    remove_workspace_context (realms, item);
     shell_realms_remove_running_realm (realms, item);
   }
 }
@@ -505,7 +541,7 @@ shell_realms_on_realm_removed (ShellRealms *realms, const gchar *realm_name)
   ShellRealmItem *item = shell_realms_realm_by_name (realms, realm_name);
   if (item) {
     shell_realm_item_set_running_flag (item, FALSE);
-    remove_workspace_context (item);
+    remove_workspace_context (realms, item);
 
     shell_realms_remove_running_realm (realms, item);
     g_hash_table_remove (realms->realms, realm_name);
@@ -545,10 +581,13 @@ shell_realms_get_default(void)
 static void
 shell_realms_init(ShellRealms *realms)
 {
+  MetaDisplay *display = shell_global_get_display(shell_global_get());
+  MetaWorkspaceManager *workspace_manager = meta_display_get_workspace_manager(display);
+
   realms->realms = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_object_unref);
   realms->running_realms = NULL;
   realms->current_realm = NULL;
-  realms->frames = shell_realms_window_frames_new (realms);
+  realms->detached_context = meta_workspace_manager_active_context(workspace_manager);
 }
 
 static void