doc: Replace uses of #NULL with %NULL

gdk/gdkdevicemanager.c

@@ -300,7 +300,7 @@ gdk_device_manager_get_property (GObject      *object,
  * Gets the #GdkDisplay associated to @device_manager.
  *
  * Returns: (nullable) (transfer none): the #GdkDisplay to which
- *          @device_manager is associated to, or #NULL. This memory is
+ *          @device_manager is associated to, or %NULL. This memory is
  *          owned by GDK and must not be freed or unreferenced.
  *
  * Since: 3.0

gdk/gdkglcontext.c

@@ -340,7 +340,7 @@ gdk_gl_context_class_init (GdkGLContextClass *klass)
   /**
    * GdkGLContext:shared-context:
    *
-   * The #GdkGLContext that this context is sharing data with, or #NULL
+   * The #GdkGLContext that this context is sharing data with, or %NULL
    *
    * Since: 3.16
    */

gtk/gtkdnd.c

@@ -1964,7 +1964,7 @@ gtk_drag_begin_internal (GtkWidget          *widget,
  * button is held down for some time.  Try to save the last event that you got
  * from the mouse, using gdk_event_copy(), and pass it to this function
  * (remember to free the event with gdk_event_free() when you are done).
- * If you can really not pass a real event, pass #NULL instead.
+ * If you really cannot pass a real event, pass %NULL instead.
  *
  * Returns: (transfer none): the context for this drag
  *

gtk/gtkgesturemultipress.c

@@ -409,7 +409,7 @@ gtk_gesture_multi_press_new (GtkWidget *widget)
  * If @rect is non-%NULL, the press area will be checked to be
  * confined within the rectangle, otherwise the button count
  * will be reset so the press is seen as being the first one.
- * If @rect is #NULL, the area will be reset to an unrestricted
+ * If @rect is %NULL, the area will be reset to an unrestricted
  * state.
  *
  * Note: The rectangle is only used to determine whether any

gtk/gtkplacessidebar.c

@@ -4448,8 +4448,10 @@ gtk_places_sidebar_class_init (GtkPlacesSidebarClass *class)
    * GtkPlacesSidebar::populate-popup:
    * @sidebar: the object which received the signal.
    * @container: (type Gtk.Widget): a #GtkMenu or another #GtkContainer
-   * @selected_item: (type Gio.File) (nullable): #GFile with the item to which the popup should refer, or #NULL in the case of a @selected_volume.
-   * @selected_volume: (type Gio.Volume) (nullable): #GVolume if the selected item is a volume, or #NULL if it is a file.
+   * @selected_item: (type Gio.File) (nullable): #GFile with the item to which
+   *     the popup should refer, or %NULL in the case of a @selected_volume.
+   * @selected_volume: (type Gio.Volume) (nullable): #GVolume if the selected
+   *     item is a volume, or %NULL if it is a file.
    *
    * The places sidebar emits this signal when the user invokes a contextual
    * popup on one of its items. In the signal handler, the application may
@@ -4919,7 +4921,7 @@ gtk_places_sidebar_get_open_flags (GtkPlacesSidebar *sidebar)
 /**
  * gtk_places_sidebar_set_location:
  * @sidebar: a places sidebar
- * @location: (allow-none): location to select, or #NULL for no current path
+ * @location: (nullable): location to select, or %NULL for no current path
  *
  * Sets the location that is being shown in the widgets surrounding the
  * @sidebar, for example, in a folder view in a file manager.  In turn, the
@@ -4979,7 +4981,7 @@ gtk_places_sidebar_set_location (GtkPlacesSidebar *sidebar,
  * gtk_places_sidebar_get_location:
  * @sidebar: a places sidebar
  *
- * Gets the currently-selected location in the @sidebar.  This can be #NULL when
+ * Gets the currently selected location in the @sidebar. This can be %NULL when
  * nothing is selected, for example, when gtk_places_sidebar_set_location() has
  * been called with a location that is not among the sidebar’s list of places to
  * show.
@@ -4989,7 +4991,7 @@ gtk_places_sidebar_set_location (GtkPlacesSidebar *sidebar,
  * function to get the location that is being referred to during the callbacks
  * for your menu items.
  *
- * Returns: (nullable) (transfer full): a GFile with the selected location, or
+ * Returns: (nullable) (transfer full): a #GFile with the selected location, or
  * %NULL if nothing is visually selected.
  *
  * Since: 3.10

gtk/gtkwidget.c

@@ -5791,7 +5791,7 @@ gtk_widget_queue_resize_no_redraw (GtkWidget *widget)
  * Unrealized widgets do not have a frame clock.
  *
  * Returns: (nullable) (transfer none): a #GdkFrameClock,
- * or #NULL if widget is unrealized
+ * or %NULL if widget is unrealized
  *
  * Since: 3.8
  */