Completely hide pointer when fullscreen-timeout is set to 0

That's the intuitive meaning of 0 here, it seems to me. The wrap from 0
to 3600 makes it easier in practice to switch to the effect that 0 used
to have: not hiding the pointer.

Closes: #126

src/main_window.c

@@ -2433,6 +2433,10 @@ cb_rstto_main_window_state_event (GtkWidget *widget,
                                         cb_rstto_main_window_hide_fs_mouse_cursor_timeout, window,
                                         cb_rstto_main_window_hide_fs_mouse_cursor_timeout_destroy);
             }
+            else
+            {
+                cb_rstto_main_window_hide_fs_mouse_cursor_timeout (window);
+            }
 
             if (rstto_settings_get_boolean_property (window->priv->settings_manager, "hide-thumbnails-fullscreen"))
             {
@@ -2560,13 +2564,9 @@ cb_rstto_main_window_motion_notify_event (RsttoMainWindow *window,
         {
             REMOVE_SOURCE (window->priv->hide_fs_mouse_cursor_timeout_id);
         }
-        else
-        {
-            gdk_window_set_cursor (gtk_widget_get_window (GTK_WIDGET (window)), NULL);
-        }
-
         if (timeout > 0)
         {
+            gdk_window_set_cursor (gtk_widget_get_window (GTK_WIDGET (window)), NULL);
             window->priv->hide_fs_mouse_cursor_timeout_id =
                 g_timeout_add_full (G_PRIORITY_DEFAULT, 1000 * timeout,
                                     cb_rstto_main_window_hide_fs_mouse_cursor_timeout, window,

src/preferences_dialog.c

@@ -367,6 +367,7 @@ rstto_preferences_dialog_init (RsttoPreferencesDialog *dialog)
     dialog->priv->fullscreen_tab.cursor_timeout_label = gtk_label_new (_("Period of inactivity (seconds):"));
     dialog->priv->fullscreen_tab.cursor_timeout_button = gtk_spin_button_new_with_range (0, 3600, 1);
     gtk_spin_button_set_digits (GTK_SPIN_BUTTON (dialog->priv->fullscreen_tab.cursor_timeout_button), 0);
+    gtk_spin_button_set_wrap (GTK_SPIN_BUTTON (dialog->priv->fullscreen_tab.cursor_timeout_button), TRUE);
     gtk_container_add (GTK_CONTAINER (dialog->priv->fullscreen_tab.cursor_hbox), dialog->priv->fullscreen_tab.cursor_timeout_label);
     gtk_container_add (GTK_CONTAINER (dialog->priv->fullscreen_tab.cursor_hbox), dialog->priv->fullscreen_tab.cursor_timeout_button);
     gtk_container_add (GTK_CONTAINER (dialog->priv->fullscreen_tab.cursor_vbox), dialog->priv->fullscreen_tab.cursor_hbox);