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>Signal Emission and Propagation

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>Signal Emission and Propagation

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>

>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 

CLASS="EMPHASIS"

>last

> handler executed. Since event signals are

all of type 

CLASS="LITERAL"

>GTK_RUN_LAST

>, this will be the default (GTK supplied)

handler, unless you connect with gtk_signal_connect_after().

>

>The way an event (say "button_press_event") is handled, is:

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>Start with the widget where the event occured.

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>Emit the generic "event" signal. If that signal handler returns

a value of TRUE, stop all processing.

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>Otherwise, emit a specific, "button_press_event" signal. If that

returns TRUE, stop all processing.

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>Otherwise, go to the widget's parent, and repeat the above two

steps.

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>Continue until some signal handler returns TRUE, or until the

top-level widget is reached.

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>Some consequences of the above are:

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>Your handler's return value will have no effect if there is a

default handler, unless you connect with gtk_signal_connect_after().

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>To prevent the default handler from being run, you need to

connect with gtk_signal_connect() and use

gtk_signal_emit_stop_by_name() - the return value only affects whether

the signal is propagated, not the current emission.

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