#16865: Dot2tex reverses Poset.show() upside down
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Reporter: jmantysalo | Owner:
Type: defect | Status: new
Priority: minor | Milestone: sage-6.7
Component: packages: optional | Resolution:
Keywords: poset, dot2tex | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by nthiery):
+1 to uniformly drawing posets with the top on top. This has annoyed
me as well.
For LaTeX / PDF output, this is taken care of by the `backward` option
of `set_latex_options` in `Poset.hasse_diagram` (called by
`Poset._latex_`).
For plots, `Poset.plot` calls `Graph.plot` on the hasse diagram, and
passes it by default the `layout=acyclic` option. The layout is then
computed by `Graph.layout_acyclic` which in turn either calls
`Graph.layout_acyclic_dummy` or `Graph.layout_graphviz` if `dot2tex`
is available.
It turns out that `Graph.layout_acyclic_dummy` orients edges pointing
up, while, `Graph.layout_graphviz` uses the default behaviour of
graphviz, namely to have edges pointing down. Hence the varying
behaviour.
Soo ... what's the cleanest way out?
One strategy:
- have an option in graphs stating whether the preferred acyclic
layout is going up or down (a generalization of the `backward` trick
in `set_latex_option`)
- make sure both `layout_acyclic_dummy` and `layout_graphviz` honor
this option.
- configure this option appropriately in the construction of the Hasse
diagram.
Another strategy would be to set as default for all graphs that the
acyclic layout shall be going up. That's simpler. But not consistent
with graphviz. It also also a larger change for the users (but only
those using acyclic layout and having dot2tex installed).
What do you think?
Cheers,
Nicolas
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Ticket URL: <http://trac.sagemath.org/ticket/16865#comment:2>
Sage <http://www.sagemath.org>
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