[evolution/gnome-43] I#2037 - EHeaderBarButton: Avoid busy loop on toggle action's 'active' change

[Milan Crha <mcrha src gnome org>]

commit a35c3a5a322dbc5e2ca441d7f260a63eee2b0d7f
Author: Milan Crha <mcrha redhat com>
Date:   Fri Sep 23 09:20:14 2022 +0200

    I#2037 - EHeaderBarButton: Avoid busy loop on toggle action's 'active' change
    
    Closes https://gitlab.gnome.org/GNOME/evolution/-/issues/2037

 src/e-util/e-headerbar-button.c | 104 ++++++++++++++++++++++++++++++++--------
 1 file changed, 85 insertions(+), 19 deletions(-)
---
diff --git a/src/e-util/e-headerbar-button.c b/src/e-util/e-headerbar-button.c
index 70dad04173..248a278ea4 100644
--- a/src/e-util/e-headerbar-button.c
+++ b/src/e-util/e-headerbar-button.c
@@ -136,8 +136,10 @@ header_bar_button_update_button (EHeaderBarButton *header_bar_button)
 }
 
 static void
-header_bar_button_clicked (EHeaderBarButton *header_bar_button)
+header_bar_button_clicked (GtkWidget *button,
+                          gpointer user_data)
 {
+       EHeaderBarButton *header_bar_button = user_data;
        GtkAction *action;
 
        if (header_bar_button->priv->action == NULL)
@@ -149,6 +151,15 @@ header_bar_button_clicked (EHeaderBarButton *header_bar_button)
                gtk_action_activate (action);
 }
 
+static void
+header_bar_button_action_activate_cb (GObject *button,
+                                     gpointer user_data)
+{
+       GtkAction *action = user_data;
+
+       gtk_action_activate (action);
+}
+
 static void
 header_bar_button_set_prefer_item (EHeaderBarButton *self,
                                   const gchar *prefer_item)
@@ -178,12 +189,63 @@ header_bar_button_transform_sensitive_cb (GBinding *binding,
        return TRUE;
 }
 
+typedef struct _ToggleActionData {
+       GWeakRef *button_weakref;
+       gulong handler_id;
+} ToggleActionData;
+
+static void
+toggle_action_data_free (gpointer ptr,
+                        GClosure *closure)
+{
+       ToggleActionData *tad = ptr;
+
+       if (tad) {
+               e_weak_ref_free (tad->button_weakref);
+               g_free (tad);
+       }
+}
+
+static void
+header_button_action_notify_active_cb (GObject *action,
+                                      GParamSpec *param,
+                                      gpointer user_data)
+{
+       ToggleActionData *tad = user_data;
+       GtkToggleButton *button;
+       gboolean active = FALSE;
+
+       button = g_weak_ref_get (tad->button_weakref);
+       if (!button)
+               return;
+
+       g_object_get (action, "active", &active, NULL);
+
+       /* The "clicked" callback calls gtk_action_activate(), which, in case
+          of the toggle action, means to flip the option, thus it calls a notification
+          about action's 'active' property change, which leads back here, causing
+          a busy loop though the signal handlers. Blocking the handler breaks the loop. */
+       if (tad->handler_id)
+               g_signal_handler_block (button, tad->handler_id);
+
+       if ((gtk_toggle_button_get_active (button) ? 1 : 0) != (active ? 1 : 0))
+               gtk_toggle_button_set_active (button, active);
+
+       if (tad->handler_id)
+               g_signal_handler_unblock (button, tad->handler_id);
+
+       g_clear_object (&button);
+}
+
 static GtkWidget *
 header_bar_button_add_action (EHeaderBarButton *header_bar_button,
                              const gchar *label,
-                             GtkAction *action)
+                             GtkAction *action,
+                             GCallback clicked_cb,
+                             gpointer clicked_cb_user_data)
 {
        GtkWidget *button;
+       gulong clicked_handler = 0;
 
        if (GTK_IS_TOGGLE_ACTION (action))
                button = gtk_toggle_button_new_with_label (label);
@@ -194,6 +256,11 @@ header_bar_button_add_action (EHeaderBarButton *header_bar_button,
 
        gtk_box_pack_start (GTK_BOX (header_bar_button), button, FALSE, FALSE, 0);
 
+       if (clicked_cb) {
+               clicked_handler = g_signal_connect_object (
+                       button, "clicked", clicked_cb, clicked_cb_user_data, 0);
+       }
+
        if (action) {
                e_binding_bind_property_full (
                        action, "sensitive",
@@ -203,10 +270,17 @@ header_bar_button_add_action (EHeaderBarButton *header_bar_button,
                        NULL, NULL, NULL);
 
                if (GTK_IS_TOGGLE_ACTION (action)) {
-                       e_binding_bind_property (
-                               action, "active",
-                               button, "active",
-                               G_BINDING_SYNC_CREATE);
+                       ToggleActionData *tad;
+
+                       gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (button),
+                               gtk_toggle_action_get_active (GTK_TOGGLE_ACTION (action)));
+
+                       tad = g_new0 (ToggleActionData, 1);
+                       tad->button_weakref = e_weak_ref_new (button);
+                       tad->handler_id = clicked_handler;
+
+                       g_signal_connect_data (action, "notify::active",
+                               G_CALLBACK (header_button_action_notify_active_cb), tad, 
toggle_action_data_free, 0);
                }
 
                header_bar_button_update_button_for_action (GTK_BUTTON (button), action);
@@ -278,16 +352,14 @@ header_bar_button_constructed (GObject *object)
 
        header_bar_button->priv->button = header_bar_button_add_action (header_bar_button,
                header_bar_button->priv->label,
-               header_bar_button->priv->action);
+               header_bar_button->priv->action,
+               G_CALLBACK (header_bar_button_clicked),
+               header_bar_button);
 
        /* TODO: GTK4 port: do not use linked buttons
         * https://developer.gnome.org/hig/patterns/containers/header-bars.html#button-grouping */
        style_context = gtk_widget_get_style_context (GTK_WIDGET (header_bar_button));
        gtk_style_context_add_class (style_context, "linked");
-
-       g_signal_connect_swapped (
-               header_bar_button->priv->button, "clicked",
-               G_CALLBACK (header_bar_button_clicked), header_bar_button);
 }
 
 static void
@@ -393,17 +465,11 @@ e_header_bar_button_add_action (EHeaderBarButton *header_bar_button,
                                const gchar *label,
                                GtkAction *action)
 {
-       GtkWidget *button;
-
        g_return_if_fail (E_IS_HEADER_BAR_BUTTON (header_bar_button));
        g_return_if_fail (GTK_IS_ACTION (action));
 
-       button = header_bar_button_add_action (header_bar_button, label, action);
-
-       g_signal_connect_object (
-               button, "clicked",
-               G_CALLBACK (gtk_action_activate), action,
-               G_CONNECT_SWAPPED);
+       header_bar_button_add_action (header_bar_button, label, action,
+               G_CALLBACK (header_bar_button_action_activate_cb), action);
 }
 
 /**