SignalHandling.md

Signal Handling in GTK-4 Python3

Default way, pre-given Signals

You can just connect to the EventListener of a Widget, Window etc. It is pretty straight forward, although there is no list that helps you to find the Signals, you need to search in the GTK 4 Documentation for everything.

# init func of your Widget/Window
def __init__(...):
  window.connect("event", eventListener)

# eventListener Func
def eventListener (params...):
  print("this event triggered yo")

How to create and use custom signals?

The fun starts when you try to hook custom signal e.g. after destroying the Window and showing it again. After ton of research, I was able to find the required GTK 4 steps.

First of all import the GObject Class from the gi Repository, and use it to setup a custom SignalObject and hook to our object, which is usually some object that is using the class Widget or Window.

Create custom Signals

import gi
gi.require_version('Gtk', '4.0')
gi.require_version('Adw', '1')
from gi.repository import GObject

# init Func of your Widget/Window
def __init__(...):
  GObject.signal_new('custom-signal', self, GObject.SignalFlags.RUN_FIRST, self,())
  self.connect("custom-signal", onCustomSignal)

# the eventListener Func
def onCustomSignal (self, ...):
    print("my custom signal bro")

Keep in mind that you have to change the param array after RUN_FIRST, if you want to give in to the eventListener multiple parameters etc. But that works fine.

Trigger Custom Signals

After initializing our nice custom Signal, we need to use emit to trigger it.

emit("custom-signal")

And you finally burned the world, good job :-)

Hint: Don't forget to use self. if you are operating in a object (e.g. using a custom class).