Understanding signals

uaknight

Here's some quick questions regarding signals:

a) Is a signal emitted even if there are no connected listening nodes?

b) Will the Global node below receive signals from ObjectA, if a connection is set up?

c) Will ObjectA receive signals from ObjectB?

root
	-- Global # autoloaded
	-- MainScene
		-- PathA
			-- ObjectA
		-- PathB
			-- ObjectB

uaknight

Remark: A strange "5." string is added when saving the post. Can't get rid of it, did not copy and paste the pseudo-code.

uaknight

I should add that according to my own testing the answer is Yes to b) and No to c). I have no clue to the answer to a).

However, I would like to have it confirmed since I cannot find anywhere an explanation of how exactly signals propagate through the node tree.

Megalomaniak

@uaknight said: Remark: A strange "5." string is added when saving the post. Can't get rid of it, did not copy and paste the pseudo-code.

The CSS just strips every line number but the fifth, however highlighting the codeblock shouldn't select the line number.

TwistedTwigleg

@uaknight said: Here's some quick questions regarding signals:

a) Is a signal emitted even if there are no connected listening nodes?

I believe that signals are emitted even if there are no listing nodes connected to the signal.

b) Will the Global node below receive signals from ObjectA, if a connection is set up?

As far as I know, signal connections do not really care where the nodes are within the scene. So long as the nodes are within the scene it should work. I think Godot internally keeps a reference to the nodes when a connection is made.

The signal connection reference might be NodePath based, in which case it may not work if you re-parent/restructure the scene tree through code while the game is running.

I think the connections are deleted when the nodes containing the signals are connected, but I do not know for sure. I've deleted connected nodes and I don't remember having any issues, so I think Godot handles deleted signals behind the scenes.

c) Will ObjectA receive signals from ObjectB?

Not by default. You'd have to connect the signals. To the best of my knowledge, there are no automatically connected signals in any of the Godot nodes by default.

I should mention that the answers are based on my experience with signals. I haven't really poked around in the Godot source code in quite awhile, so things may be different. :smile:

uaknight

Thanks for the help!

a) Ok. I think however that it would had been better if no signals were emitted if no connection was set up. You might have temporaryly signals which are not in use all the time. I f you have a lot of them, it would have been more efficient if they were never emitted. I mean if it's emitted then it must be checked with every other node in the scene tree to see if it's intercepted.

On the other hand, if there's a list of the connections made, then the signal would only need to check with the objects in the list, if I understand it correctly.

b) I didn't think of it like that the autoloaded scripts were part of the scene, but it's good that they are and that signals work between them.

On c) I was a bit unclear. I meant after the connection had been made.

The signal connection reference might be NodePath based, in which case it may not work if you re-parent/restructure the scene tree through code while the game is running.

Interesting, I think this is why it didn't work for me. The testing was done in my main project and that is by now quite large and complex. When testing in a vanilla project with minimal code, ObjectA and ObjectB succeed in signalling each other.