Dear graph/posets devs,
Due to urgent needs for Sage days 20, I just rebased and worked
further on my patch for #7004:
Refactor the graph layout code, and add interface with graphviz
It is now up on trac for review. See the ticket description for what
was changed. The main improvement from the user point of view is that
it is more modular, allowing for using any layout algorithm
(circular/spring/planar/...) with any plot function (graph_editor,
plot, save, plot3d), when meaningful. There are a couple design
questions and TODO's left in the ticket description which I reproduce
here for discussions.
So here is what remains to do, now in this ticket, or later:
* Double check all the logic to make sure it is backward compatible
There are not that many tests for the graph layout code (because it
is non trivial to test). So please recreate all your favorite graph
plots and see if there is anything broken.
* graph_editor was using iterations=1000 as default. Was there a
reason? If yes, do we want to set this up as default value for all
layouts?
* What should be the default layout algorithm?
* Planar layout when the graph is planar
* acyclic if acyclic
* spring otherwise
* The spring option for graded layouts does not work: the plot get
completely squished horizontally. Could someone please help me
debug this?
sage: G = posets.[wiki:IntegerPartitions](3).hasse_diagram()
sage: G.plot(layout="acyclic_dummy", spring = True)
To be compared with:
sage: G.plot(layout="acyclic_dummy")
* Find a better name for acyclic_dummy. Once the spring option will
be functional, this could be set to the default value, and the
layout renamed to acyclic_spring.
* Choose a good option name for the direction of growth of acyclic
layout, and a good default value. Merge this with the option for
tree layout (tree_orientation).
orientation = "up" (as for tree) ?
rankdir = "BT" (as in graphviz)?
* A lot of code is doing things very similar to dot2tex. Maybe things could be
merged.
* Implement the various options for both latex constructions (tikz or dot2tex)
* Implement the default layout of standard graphs using a
default_layout method rather than at construction time.
Notes:
- Up to fixing a couple things after this discussion, the patch
should be essentially ready. As much as possible, I'd rather have
it not rot away again. Quick comments and reviews would be most
welcome!
- I am a bit worried about conflicts with #7608. Indeed, besides its
main changes which are well localized and far from what #7004
touches, the patch up on #7608 does trivial edits almost everywhere
in the graph code (apparently fixing spurious end of line spaces).
I would suggest to either remove those trivial edits from #7608, or
to rebase it on #7004 (which will be much easier than the
converse).
Thanks in advance!
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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