Installs an accelerator that will cause the named action to be activated when the key combination specificed by accelerator is pressed.
accelerator must be a string that can be parsed by gtk_accelerator_parse(), e.g. "<Primary>q" or “<Control><Alt>p”.
action_name must be the name of an action as it would be used in the app menu, i.e. actions that have been added to the application are referred to with an “app.” prefix, and window-specific actions with a “win.” prefix.
GtkApplication also extracts accelerators out of “accel” attributes in the gio.MenuModels passed to Application.setAppMenu and Application.setMenubar, which is usually more convenient than calling this function for each accelerator.
the name of the action to activate
parameter to pass when activating the action, or NULL if the action does not accept an activation parameter
Deprecated: Use Application.setAccelsForAction instead