"""Graphviz placement for ``andrey.viz``, through pygraphviz (the ``viz`` extra).
Graphviz only places the nodes; ``andrey.viz`` still draws them. Each node is laid out as a box the
size of what the drawing puts there, its circle and the label under it, so Graphviz leaves room
for the labels.
"""
from __future__ import annotations
from collections.abc import Mapping
from typing import TYPE_CHECKING
from andrey.core.structure import ARROW, CIRCLE, TAIL, GraphStructure
from . import _svg
if TYPE_CHECKING:
import pygraphviz
ENGINES = ("dot", "neato", "fdp", "sfdp", "circo", "twopi", "osage", "patchwork")
INSTALL = 'Graphviz layouts need pygraphviz: pip install "andrey-core[viz]".'
_ARROWS = {ARROW: "normal", CIRCLE: "odot"} # a tail draws no mark
def available() -> bool:
"""Whether pygraphviz imports."""
try:
import pygraphviz # noqa: F401
except ImportError:
return False
return True
[docs]
def to_graphviz(
structure: GraphStructure, options: Mapping[str, object] | None = None
) -> pygraphviz.AGraph:
"""Return ``structure`` as a Graphviz graph.
Parameters
----------
structure : GraphStructure
Any kind. Node ``k`` is named ``"k"`` and carries its label as ``label``; each edge keeps
its endpoint marks as Graphviz arrow shapes: ``normal`` for an arrowhead, ``odot`` for a
circle, none for a tail.
options : mapping of str to object or None, default=None
Graphviz graph attributes, such as ``{"rankdir": "TB", "nodesep": 0.5}``. Causes run left
to right (``rankdir="LR"``) unless ``options`` says otherwise.
Returns
-------
pygraphviz.AGraph
A directed graph. A directed edge runs from tail to arrowhead; an undirected edge has
``dir="none"``; any other edge has ``dir="both"``, with ``arrowhead`` and ``arrowtail``
set from its marks; a ``digraph`` 2-cycle becomes two directed edges. Render or lay it out
with pygraphviz, or pass it to any Graphviz tool through ``to_string()``.
Raises
------
ImportError
If pygraphviz is not installed.
"""
try:
import pygraphviz
except ImportError as err:
raise ImportError(INSTALL) from err
n = int(structure.n_nodes)
labels = list(structure.labels) if structure.labels is not None else [str(k) for k in range(n)]
graph = pygraphviz.AGraph(directed=True, strict=False)
graph.graph_attr["rankdir"] = "LR"
graph.graph_attr.update({key: str(value) for key, value in (options or {}).items()})
graph.node_attr["shape"] = "circle"
for k in range(n):
graph.add_node(str(k), label=labels[k])
for row in structure.to_edges():
i, j = int(row["i"]), int(row["j"])
mark_i, mark_j = int(row["mark_i"]), int(row["mark_j"])
if i == j: # a self-loop is one directed edge
graph.add_edge(str(i), str(i))
elif (mark_i, mark_j) == (TAIL, ARROW):
graph.add_edge(str(i), str(j))
elif (mark_i, mark_j) == (ARROW, TAIL):
graph.add_edge(str(j), str(i))
elif (mark_i, mark_j) == (TAIL, TAIL):
graph.add_edge(str(i), str(j), dir="none")
elif structure.kind == "digraph": # arrowheads at both ends: a 2-cycle
graph.add_edge(str(i), str(j))
graph.add_edge(str(j), str(i))
else:
head, tail = _ARROWS.get(mark_j, "none"), _ARROWS.get(mark_i, "none")
graph.add_edge(str(i), str(j), dir="both", arrowhead=head, arrowtail=tail)
return graph
def positions(
structure: GraphStructure, engine: str, options: Mapping[str, object] | None = None
) -> dict[int, tuple[float, float]]:
"""Each node's center as Graphviz ``engine`` places it, in points, ``y`` downward."""
graph = to_graphviz(structure, options)
n = int(structure.n_nodes)
labels_inside = all(len(graph.get_node(str(k)).attr["label"]) <= 2 for k in range(n))
graph.node_attr.update(shape="box", fixedsize="true")
for k in range(n):
node = graph.get_node(str(k))
width, height = _svg.footprint(node.attr["label"], labels_inside)
node.attr.update(label="", width=width / 72, height=height / 72)
graph.layout(prog=engine)
placed = {}
for k in range(n):
x, y = (float(v) for v in graph.get_node(str(k)).attr["pos"].split(",")[:2])
placed[k] = (x, -y) # Graphviz's y grows upward
return placed
