[glib] GSimpleAction: Clarify/fix @parameter(_type) docs

[Daniel Boles <dboles src gnome org>]

commit 75021c6c6ea8a5f094ef85ebf32f2f99c71cd173
Author: Daniel Boles <dboles src gnome org>
Date:   Sun Apr 8 11:39:32 2018 +0100

    GSimpleAction: Clarify/fix @parameter(_type) docs
    
    If something is nullable, it's always helpful to identify what NULL
    means. Also, this is not the parameter for the .activate() vfunc, as we
    take that over: rather, it is the parameter for the ::activate signal.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=795070

 gio/gsimpleaction.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/gio/gsimpleaction.c b/gio/gsimpleaction.c
index 54c554087..0560ae6d2 100644
--- a/gio/gsimpleaction.c
+++ b/gio/gsimpleaction.c
@@ -371,7 +371,8 @@ g_simple_action_class_init (GSimpleActionClass *class)
   /**
    * GSimpleAction::activate:
    * @simple: the #GSimpleAction
-   * @parameter: (nullable): the parameter to the activation
+   * @parameter: (nullable): the parameter to the activation, or %NULL if it has
+   *   no parameter
    *
    * Indicates that the action was just activated.
    *
@@ -591,7 +592,8 @@ g_simple_action_set_state_hint (GSimpleAction *simple,
 /**
  * g_simple_action_new:
  * @name: the name of the action
- * @parameter_type: (nullable): the type of parameter to the activate function
+ * @parameter_type: (nullable): the type of parameter that will be passed to
+ *   handlers for the #GSimpleAction::activate signal, or %NULL for no parameter
  *
  * Creates a new action.
  *
@@ -616,7 +618,8 @@ g_simple_action_new (const gchar        *name,
 /**
  * g_simple_action_new_stateful:
  * @name: the name of the action
- * @parameter_type: (nullable): the type of the parameter to the activate function
+ * @parameter_type: (nullable): the type of the parameter that will be passed to
+ *   handlers for the #GSimpleAction::activate signal, or %NULL for no parameter
  * @state: the initial state of the action
  *
  * Creates a new stateful action.