20.2. Signal Emission and Propagation
Signal emission is the process whereby GTK+ runs all handlers for
a specific object and signal.
First, note that the return value from a signal emission is the
return value of the last handler executed. Since event signals are all of
type RUN_LAST, this will be the default (GTK+ supplied)
handler, unless you connect with the
The way an event (say "button_press_event") is handled,
Start with the widget where the event occurred.
Emit the generic "event" signal. If that signal handler
returns a value of TRUE, stop all processing.
Otherwise, emit a specific, "button_press_event" signal. If
that returns TRUE, stop all processing.
Otherwise, go to the widget's parent, and repeat the above
Continue until some signal handler returns
TRUE, or until the top-level widget is reached.
Some consequences of the above are:
Your handler's return value will have no effect if there is
a default handler, unless you connect with
To prevent the default handler from being run, you need to
connect with connect() and use
emit_stop_by_name() - the return value only affects
whether the signal is propagated, not the current emission.