lookup

Given the name of the signal and the type of object it connects to, gets the signal's identifying integer.

Emitting the signal by number is somewhat faster than using the name each time.

Also tries the ancestors of the given type.

The type class passed as itype must already have been instantiated (for example, using class_ref) for this function to work, as signals are always installed during class initialization.

See @new for details on allowed signal names.

Parameters:

name	the signal's name.
itype	the type that the signal operates on.

Returns:

the signal's identifying number, or 0 if no signal was found.