GTK/GObject detailed_signal parameter

Question

In the GObject Reference Manual, it denotes that for a function:

   g_signal_connect(instance, detailed_signal, c_handler, data)

A detailed_signal string parameter of form "signal-name::detail" is desired. My initial understanding of that is that there are predefined signal details to pass in. If that is the case, where can I find a list of these? If not, then what exactly does it mean, as the manual doesn't make that too terribly obvious.

Answer 1

The ::detail part of the signal name is optional. If a signal takes a detail parameter, then it will say so in the signal's documentation. Otherwise you can ignore it.

The only signal that I'm aware of that actually uses a detail parameter, is the notify signal of GObject. The notify signal without a detail fires whenever any property changes on the object, so it's fairly useless. But if you connect to the notify::visible signal, then it will fire whenever the object's visible property changes.

Answer 2

Unless things have changed a lot recently, there's no complete, official list of signals. The predefined signals depend entirely on what technologies you're using.

What you can do is look at the online documentation for the GObject instance classes you're working with. For instance, if you're working with GtkButton, you can look it up online and find out that it emits six signals (activate, clicked, enter, leave, pressed, released). GtkButton is derived from GtkContainer, which also emits several documented signals that can potentially be emitted by GtkButton. And GtkContainer is derived from GtkWidget, which emits many documented signals which can potentially be emitted by GtkButton.

If you find an object isn't emitting a kind of signal you expect, you might also look in the source code for that object, because sometimes objects emit undocumented signals,