I still think dot could be reimplemented in d3. I agree dot is very expressive but it's starting to feel like TeX where it works great until you need to mix it into more recent applications.
There used to be several commercial alternatives in this space (browser graph drawing): jgraph/mxgraph, tom sawyer, yworks (yed) had a browser library. It's curious that these never get discussed when this topic comes up. It's been a few years, so they may no longer around. The hard part of graph visualization has always been the layout algorithms. I tend to think that the ubiquity of graphviz has been an impediment in this area (imo)
Considering I'm still getting paid, I can say that yWorks is still around ;-) Since about a month with a new major version of our JS library as well. mxGraph apparently transitioned to open-source with paid subscription by now – we'll see how well that works out.
I guess the reason that commercial solutions rarely get discussed in such contexts is that they are quite expensive if you're a single developer hacking away at a side project. Even our cheapest license is already five figures (considering Tom Sawyer also rather target enterprise customers they won't be cheaper) and to be honest, I'd think hard about paying that if I'm not absolutely sure I'd get the money back somehow. For larger companies it's less of an issue, of course, or the cost just gets billed to their customer as part of the project cost.
Ah I see, since you're on the inside I'll ask, why haven't you (i.e. yworks) implemented the so-called delta drawing for flow charts? Seems like that would be a real differentiator? Or have you and I haven't been paying attention?
I have to admit, I'm not familiar with that¹. Do you have a link to a paper or something; I could ask our layout team.
But probably the answer will be that few customers asked so far and/or it might be fairly easy to accomplish with customizing one of the existing layout algorithms. We did something similar with our example BPMN implementation where a pre-processing step applied constraints for the hierarchic layout based on the node/edge types in the diagram. The vast majority of things customers ask of us are actually fairly easy to implement without necessarily having them in the library. So we have very few layout algorithms that are applicable to exactly one kind of diagram (family trees are an exception, but even that is just a wrapper around a more general-purpose algorithm).
The advantage is that there are very many knobs and configuration options to fiddle with to get the layout you want. The disadvantage is that there are very many knobs and configuration options to fiddle with, where having special layouts for certain types of graphs might be easier but not as flexible.
In the end, it's a library and the users (from our perspective) are developers and those shouldn't shy away from writing some code. It would be nice to also appeal to people who just want some data laid out nicely. To some extent that works already², but such wishes have to be balanced with what people are willing to pay for :-)
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¹ Happens often with very domain-specific graphs; last thing mentioned I didn't know was some kind of diagram to describe pipes, valves, and water flows in buildings.
Your ¹ sounds like the Sankey diagram[1]. I only know about these because at one time matplotlib advertised support. And because of the classic diagram that Tufte promotes [2].
