GraphMachine: set proportional font or allow caller control about transitions HOT 3 OPEN

Hello @ulemanstreaming,

the diagrams module supports pygraphviz and graphviz backends and get_graph will return either pygraphviz or graphviz graph objects which you can edit to your liking. If you use pygraphviz (default) you could edit pygraphviz.AGraph attributes like this:

from transitions.extensions import GraphMachine

states = ["welcome", "industry", "usecase", "load_data"]
transitions = [
    ["next_step", "welcome", "industry"],
    ["next_step", "industry", "usecase"],
    ["next_step", "usecase", "load_data"],
    ["previous_step", "load_data", "usecase"],
    ["previous_step", "usecase", "industry"],
    ["previous_step", "industry", "welcome"],
]

m = GraphMachine(states=states, transitions=transitions, initial='welcome')
graph = m.get_combined_graph()
graph.graph_attr["fontname"] = "arial"
graph.edge_attr["fontname"] = "arial"
graph.node_attr["fontname"] = "arial"
graph.draw('graph_arial.png', prog='dot')

But there is also a mechanism for 'global' graph settings:
The dot/graphviz settings are defined as class members (Graphmachine.machine_attributes, Graphmachine.style_attributes). For global changes you can either 'monkey patch' those or use inheritance and create your own configuration. For a start, you can copy the above mentioned configurations.

GraphMachine uses MarkupMachine to get a dictionary representation of the current machine configuration (states, transitions, etc.). You could override get_markup_config to intercept this process and add a capitalised label.

from transitions.extensions import GraphMachine
from copy import deepcopy

states = ["welcome", "industry", "usecase", "load_data"]
transitions = [
    ["next_step", "welcome", "industry"],
    ["next_step", "industry", "usecase"],
    ["next_step", "usecase", "load_data"],
    ["previous_step", "load_data", "usecase"],
    ["previous_step", "usecase", "industry"],
    ["previous_step", "industry", "welcome"],
]

machine_attributes = deepcopy(GraphMachine.machine_attributes)
style_attributes = deepcopy(GraphMachine.style_attributes)

machine_attributes["fontname"] = "arial"
style_attributes["node"]["default"]["fontname"] = "arial"
style_attributes["edge"]["default"]["fontname"] = "arial"


class ArialGraph(GraphMachine):

    machine_attributes=machine_attributes
    style_attributes=style_attributes

    def get_markup_config(self):
        config = super(ArialGraph, self).get_markup_config()
        for state in config['states']:
            state['label'] = state['name'].capitalize()
        return config


ag = ArialGraph(states=states, transitions=transitions, initial='welcome')
ag.get_combined_graph().draw('graph_inherited.png', prog='dot')

So this is how you could achieve what you are looking for as of now. However, if you have some ideas about how to streamline this process and make it more user friendly let me know. Adding more parameters to the constructor is something I'd like to avoid since there are already so many of them.

from transitions.

Instead of

graph.graph_attr["fontname"] = "arial"
graph.edge_attr["fontname"] = "arial"
graph.node_attr["fontname"] = "arial"

you could also pass them as arguments to dot:

graph.draw('graph_args.png', prog='dot', args="-Gfontname=Arial -Efontname=Arial -Nfontname=Arial")

from transitions.

Thank you @aleneum . These are very helpful suggestions, and sufficient for my current purposes.

• Using command line arguments is effective, though it feels a bit hacky.
• I already subclass GraphMachine (using your suggested Alternative initialization pattern), so there's no need for me to create a separate subclass. I work in a Jupyter notebook, which can readily display a PNG if it's returned by a method named _repr_png_. So I simply implement that, along with your suggestions for get_markup_config() and the *_attribute data members. I also use a smaller font inside the graph and replace underscore with space in the state labels. This leads to:

class Wizard(GraphMachine):
    machine_attributes = deepcopy(GraphMachine.machine_attributes)
    style_attributes   = deepcopy(GraphMachine.style_attributes)
    
    machine_attributes['fontname']                  = 'arial'
    style_attributes['node']['default']['fontname'] = 'arial'
    style_attributes['edge']['default']['fontname'] = 'arial'
    style_attributes['node']['default']['fontsize'] = 9
    style_attributes['edge']['default']['fontsize'] = 9

    def __init(...)
        ...

    def get_markup_config(self):
        config = super(Wizard, self).get_markup_config()
        
        for state in config['states']:
            state['label'] = state['name'].capitalize().replace('_', ' ')
        return config
    
    def _repr_png_(self, **kwargs):
        return self.get_graph(title=self._title, **kwargs).draw(None, prog='dot', format='png')

So, it works. I have no suggestions for making it easier beyond documenting these tricks, or maybe doing more with the kwargs parameter in get_graph(). I agree that loading up the constructor with more parameters is not great; if you really wanted to give callers more control, adding one or a few methods to set style attributes might be preferable.

This issue can be closed as far as I'm concerned.

from transitions.