Generalized inputs/outputs

[senritsu]

Currently nodes can only be linked to other nodes.

For more complex behaviours it might be interesting to populate properties from inputs that can be linked to outputs of other nodes. This would enable applications like making a graph similar to visual scripting tools or shader editors.

Effectively this would require generalization of links between nodes/properties to take the Type of the input/output into account, to limit what can be connected to it. Outputs of a subclass of GraphNode could be connected like it is now, outputs of different types can be connected to inputs of a matching (or compatible) type.

This would also allow restrictions to what kind of nodes can follow a node in the graph, for example a "Choose response" node in a dialogue could be restricted to only be followed by a "Show response text" node.