I know you can send messages to a canvas to create objects, move things, make connections, etc.

Is there conversely a way to receive messages from a canvas? For example, can you get a message when an object is created or moved?

The use case I am specifically after right now is to create a conditional that checks if a subpatch is open or not. I can send vis 1 to the subpatch to open the window, but can I receive a vis 1 or vis 0 (or some other equivalent notification) when the window is opened or closed by other means?

@pure_datum [pdcontrol] has this feature for patches and subpatches. It is described in the help file.

@pure_datum I think you're looking for [receivecanvas] from iemguts

@seb-harmonik.ar Right, [pdcontrol] doesn't react on opening the subpatch, it can only be questioned if the subpatch is opened.

@ingox oh yeah I didn't read the question carefully enough. is the need to be notified when a canvas is opened, or to find out if a canvas is open?

Oh these are both super useful to know about! They didn't come up in my searches. Thanks. I could probably make either one work for my case. I'll probably try out pdcontrol in order to stay vanilla.

If anyone is curious, what I specifically want to do is to avoid writing to a table unless the window is open. I know the actual graphical table doesn't update if the subpatch is closed, but I want to save some cpu usage by actually not writing to it unless it's open.