installProperties
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 a delegate), or remember the @first_prop offset and add it to the values in the enum@Gtk.EditableProperties enumeration to get the property IDs for these properties.
Return
the number of properties that were installed
Parameters
a GObjectClass
property ID to use for the first property