[gtk/backports-for-4-4: 14/16] editable: Clarify the docs

[Matthias Clasen <matthiasc src gnome org>]

commit 8407ebe1d8a3c15e40f0d5a01f74e46c59c2430b
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Aug 31 08:41:45 2021 -0400

    editable: Clarify the docs
    
    Make it clear that your class must have all the editable properties
    already before you call the (confusingly named) function
    gtk_editable_install_properties.

 gtk/gtkeditable.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkeditable.c b/gtk/gtkeditable.c
index c8386afe21..a9517e1c1e 100644
--- a/gtk/gtkeditable.c
+++ b/gtk/gtkeditable.c
@@ -945,11 +945,15 @@ gtk_editable_set_enable_undo (GtkEditable *editable,
  * @object_class: a `GObjectClass`
  * @first_prop: property ID to use for the first property
  *
- * Installs the `GtkEditable` properties for @class.
+ * Overrides the `GtkEditable` properties for @class.
  *
  * This is a helper function that should be called in class_init,
  * after installing your own properties.
  *
+ * Note that your class must have "text", "cursor-position",
+ * "selection-bound", "editable", "width-chars", "max-width-chars",
+ * "xalign" and "enable-undo" properties for this function to work.
+ *
  * To handle the properties in your set_property and get_property
  * functions, you can either use [func@Gtk.Editable.delegate_set_property]
  * and [func@Gtk.Editable.delegate_get_property] (if you are using