Allow custom dot attributes in Diagram constructor

[deadmeu]

Allow custom graph, node, and edge attributes to be passed in to the Diagram constructor. This allows the user to configure the output image using whatever configuration of attributes they would like.

[mingrammer]

Could you please provide a practical example use custom options?

Because I want to hide the internal implementation-specific options to users who don't know or even who know the Graphviz.

The outformat, direction options are also dot attributes, but provided as normal arguments. So users don't have to know Graphviz options.

[deadmeu]

I was looking to render with a transparent background, though I think providing some mechanism to allow users to customise the rendered image is important.

Since Graphviz is a hard dependency of this project, and there is plenty of documentation available online, I figured it would be ok to allow users to pass in their own Graphviz configuration.

[mingrammer]

Your opinions are persuasive to me. I accept it :)

Thanks for your contribution!

[deadmeu]

Thanks, I really hate drawing diagrams using popular visual editors, so the natural language expression using python, along with the awesome pre-provided icons, intrigues me.

I found the changes in this PR to be quite compelling in being able to rapidly prototype the design. Take a look: https://streamable.com/f9zf1

Maybe as a future edition we could develop something like a DiagramOptions class, decoupling the Graphviz attributes from Diagrams? That way, we would only need to pass in a single options parameter into the constructor of the Diagrams class which would contain all of the configuration, including the existing outformat and direction options. I'm not very experienced with Python though so there may be a more Pythonic way to handle this.

[mingrammer]

Wow! I'm glad to see that someone makes a demo video using a library I made :) Thank you.

The idea of DiagramOptions class sounds good to me. We can more develop this idea. I'm willing to support option class in the future. (while keeping the backward compatibility)