Qt's state machine as a node graph?

Question

I am trying to figure out how to use a node graph for processing a set of data. It is for an application that manipulates sound data, much like if you had a bunch of pedals for your guitar. You have some nodes with predefined procedures connected to each other in a directed graph. Each takes a turn to process the data, and when one is finished it gives a signal to the next node to do it's thing. The idea is you piece these nodes together using the ui.

I am using Qt for creating the UI, and as such I was looking through it's documentation to see if there was something I could use for the above mentioned problem. And I found the Qt state machine, from what I can read it seems to do what I need, a state is entered, you do some processing, when it is done a finished signal is given, and the next state in the graph is started. Also the fact that you could nest states, giving me the ability to create new nodes by combining existing ones, seems like an attractive idea.

However the state machine was created for changing the attributes of widgets (changing their state) and not for wrapping procedures. For example, a button is pressed and the state machine changes the state of another widget, and e.g. if the button is released the state is swapped back.

So, anyone with more experience, with Qt, the state machine, or processing by node graphs, who could give me a hint whether or not tweaking the state machine to wrap my procedures will work. Or, if there is something else in the Qt library I could use?

Answer 1

I used QStateMachine for online message processing (online in the sense of online algorithm) and it worked fine, there weren't restrictions just because the original idea was to modify widgets.

However, personally I would not use it for your project because a state machine is not exactly what you describe. It might be possible to bend it to your needs but it would certainly be weird. A better solution would be to make a nice polymorphic OO model with your "effects" having a base class and a decoupled graph implementation to connect them. You can use Qt signals to signal finishing the the graph to take the next step. It is also easier to build your custom graph from data than create the states and transitions for the state machine dynamically.