Add a GCancellable to EActivity.

EActivity now uses a GCancellable to manage cancellations, instead of
having its own redundant cancellation API.  API changes are as follows:

  + e_activity_get_cancellable()
  + e_activity_set_cancellable()

  - e_activity_cancel()
  - e_activity_is_cancelled()
  - e_activity_get_allow_cancel()
  - e_activity_set_allow_cancel()

EActivity's "cancelled" signal remains, but only as a repeater for
GCancellable::cancelled signals.  It should not be emitted directly.

The presence of a GCancellable implies that cancellation is allowed.
EActivity does not create its own default GCancellable, it has to be
given one.

If a CamelOperation (cast as a GCancellable) is given, EActivity will
configure itself to listen for status updates from the CamelOperation
and propagate the information to its own "primary-text" and "percent"
properties.

These changes allowed me to start cleaning up some of the incredibly
convoluted logic in mail-mt.c -- in particular, mail_operation_status()
is completely gone now.  mail-mt.c is still in a transitional state --
much more significant changes coming soon.

2 files changed, 26 insertions, 16 deletions

diff --git a/shell/e-shell-taskbar.c b/shell/e-shell-taskbar.c
index a82d3d6246..47f900ae3e 100644
--- a/shell/e-shell-taskbar.c
+++ b/shell/e-shell-taskbar.c
@@ -96,12 +96,13 @@ shell_taskbar_activity_add (EShellTaskbar *shell_taskbar,
 	GtkBox *box;
 	GtkWidget *proxy;
 
+	/* Proxy widgets manage their own visibility.
+	 * Don't call gtk_widget_show() on it here. */
 	proxy = e_activity_proxy_new (activity);
 	box = GTK_BOX (shell_taskbar->priv->hbox);
 	gtk_box_pack_start (box, proxy, TRUE, TRUE, 0);
 	gtk_box_reorder_child (box, proxy, 0);
 	gtk_widget_show (GTK_WIDGET (box));
-	gtk_widget_show (proxy);
 
 	g_hash_table_insert (
 		shell_taskbar->priv->proxy_table,
@@ -176,13 +177,14 @@ shell_taskbar_get_property (GObject *object,
 }
 
 static gboolean
-disconnect_remove (EActivity      *activity,
-		   EActivityProxy *proxy,
-		   EShellTaskbar  *shell_taskbar)
+disconnect_remove (EActivity *activity,
+                   EActivityProxy *proxy,
+                   EShellTaskbar *shell_taskbar)
 {
-	g_signal_handlers_disconnect_matched
-		(activity, G_SIGNAL_MATCH_DATA,
-		 0, 0, NULL, NULL, shell_taskbar);
+	g_signal_handlers_disconnect_matched (
+		activity, G_SIGNAL_MATCH_DATA,
+		0, 0, NULL, NULL, shell_taskbar);
+
 	return TRUE;
 }
 
@@ -217,9 +219,8 @@ shell_taskbar_dispose (GObject *object)
 		priv->hbox = NULL;
 	}
 
-	g_hash_table_foreach_remove (priv->proxy_table,
-				     (GHRFunc) disconnect_remove,
-				     object);
+	g_hash_table_foreach_remove (
+		priv->proxy_table, (GHRFunc) disconnect_remove, object);
 
 	/* Chain up to parent's dispose() method. */
 	G_OBJECT_CLASS (e_shell_taskbar_parent_class)->dispose (object);
diff --git a/shell/e-shell.c b/shell/e-shell.c
index 93832ec7fe..28abe028dc 100644
--- a/shell/e-shell.c
+++ b/shell/e-shell.c
@@ -240,8 +240,11 @@ shell_prepare_for_offline (EShell *shell)
 	if (shell->priv->preparing_for_line_change != NULL)
 		return;
 
-	shell->priv->preparing_for_line_change =
-		e_activity_new (_("Preparing to go offline..."));
+	shell->priv->preparing_for_line_change = e_activity_new ();
+
+	e_activity_set_primary_text (
+		shell->priv->preparing_for_line_change,
+		_("Preparing to go offline..."));
 
 	g_object_add_toggle_ref (
 		G_OBJECT (shell->priv->preparing_for_line_change),
@@ -290,8 +293,11 @@ shell_prepare_for_online (EShell *shell)
 	if (shell->priv->preparing_for_line_change != NULL)
 		return;
 
-	shell->priv->preparing_for_line_change =
-		e_activity_new (_("Preparing to go online..."));
+	shell->priv->preparing_for_line_change = e_activity_new ();
+
+	e_activity_set_primary_text (
+		shell->priv->preparing_for_line_change,
+		_("Preparing to go online..."));
 
 	g_object_add_toggle_ref (
 		G_OBJECT (shell->priv->preparing_for_line_change),
@@ -349,8 +355,11 @@ shell_prepare_for_quit (EShell *shell)
 	if (shell->priv->preparing_for_quit != NULL)
 		return;
 
-	shell->priv->preparing_for_quit =
-		e_activity_new (_("Preparing to quit..."));
+	shell->priv->preparing_for_quit = e_activity_new ();
+
+	e_activity_set_primary_text (
+		shell->priv->preparing_for_quit,
+		_("Preparing to quit..."));
 
 	g_object_add_toggle_ref (
 		G_OBJECT (shell->priv->preparing_for_quit),