Rocs general graph layout implementation question.

[Adriaan de Groot]

Hi Dilson,

I Have An Opinion. (I write that with caps to indicate that this is like Owl, 
in the Winnie-the-Pooh stories: someone who pretends to be very wise but 
doesn't have a handle on things at all; so this is just one thing you might 
consider)

On Monday, 1 June 2020 14:23:07 CEST Dilson Guimarães wrote:
> I am a GSoC student working on the graph layout (drawing) capabilities of
> Rocs <https://kde.org/applications/education/org.kde.rocs>. I am going to
> include graph layout algorithms to compute the positions for all the graph
> vertices, satisfying some constraints such as keeping every vertex inside
> the drawing area.

Inside the *drawing* area. Oh. There's existing code with several variations 
to move a generated graph into a sensible location on the canvas, but bear in 
mind that the graph can be bigger than the viewport / drawing area.

> I have two options here: use an existing library to do
> that or implement the algorithms directly. 

Re-use and re-cycle. I'd typically suggest using a library if the interface 
impedance isn't too large. However, ROCS is special: it's also an *example* 
and learning tool about graphs, and graph layout is something that might be 
interesting from that perspective. So consider doing it in Javascript (ugh?) 
so that it can be run through the interpreter in ROCS.


> The graph layout algorithms I would have to implement are optimization
> algorithms, which I have some experience with because I do research on
> optimization. A positive thing about implementing the algorithms myself is
> that I would have more flexibility to make them better suited for Rocs.
> Besides that, on future phases of this GSoC project, I will implement graph
> layout algorithms for specific kinds of graph. For those, I did not find a
> library ready for use.

This suggests harder: do it yourself (maybe not in JS though)

> 
> On the other hand, going with the library can speed things up. I found one
> library that seems to provide a good amount of functionality. Its name is
> libcola <https://www.adaptagrams.org/documentation/libcola.html> and its
> GitHub repository can be found here
> <https://github.com/mjwybrow/adaptagrams>. Maybe there are some issues
> about adding more dependencies.

adaptagrams itself does not look like it is packaged much; it doesn't even 
have a tagged release.

[ade]