:construction: Generating an automatic Graph layout

[emmenlau]

I'm under the impression that QuickQanava currently does not do any automatic graph layout, is that correct? Or did I overlook something?

I've found that there are some Javascript libraries around that could be a cool combination with QuickQanava for this task. For example https://github.com/dagrejs/dagre is MIT licensed, and does only do layout, no rendering. So it should fit very well with QML and QuickQanava. The getting started example is almost trivial: https://github.com/dagrejs/dagre/wiki#using-dagre

Would that be something that can be considered? I may be able to help with such an (optional) integration, if that is something worthwhile for QuickQanava?

Or what is your overall take on the subject?

[cneben]

Hi @emmenlau sorry again for the answer delay, currently having too much work for serious open source contributions.

QuickQanava initially include c++ tree layout algorithm and a custom "force-spring" implementation (10 years ago!). I remove that code because:

• It was synchronous and there is no trivial strategy to execute it in a separate thread (locking or inefficient full graph copy)
• Adding locking on nodes x/y/width/height properties has significant cost even for users not interested in auto-layout.

I have more and more interest for auto-layout recently especially for force spring and tree layout algorithms (not necessarily an "online/progressive" version) for a private use-case, so we might consider putting effort in it.

Have you actually tried to import and use a packaged version of Dagre from QML ?

[emmenlau]

Thanks for the thumbs-up, @cneben !

I have not tried using Dagre from QML yet, but I'm very interested in that. In the past, I did use some pure Javascript libraries from QML, and in the cases that I tried, it was quite easy to get something up and running. However I think I will not have time this or next week.

Let me know if you will take a look, and otherwise I'll go for it sooner or later...

[emmenlau]

I have been considering this for a bit more, and here are my thoughts so far. I think adding Dagre as a javascript library is most likely not too hard, and neigher should be using Dagre to generate a graph layout.

I would assume that the main effort is in integrating the automatic graph layout together with manual graph layout in a sensible way. I.e. some relevant questions:

• Should the automatic layout only be triggered with some manual action, like a button click or key press? This would be important to avoid messing up a manual layout that the user wants to preserve.
  • What is sensible for example when adding new nodes? Should they be placed using automatic layout? But this may mess up the current (manual) graph layout completely, hard to predict...
• It may be helpful to combine automatic layout with Qt animations, so that nodes are moved to new positions, rather than jumping to new positions. Otherwise it can be quite hard for the user to see what is going on...

Just my two cents...