[BUG] PointDrawTool does not work for 'graph_renderer.node_renderer'

[FabiJa]

Hi,
the PointDrawTool does not work with an imported networkx graph. I am asking because I would like to interactively move the nodes of a networkx graph.

My minimal code example is the following:

import networkx as nx

from bokeh.io import show, output_file
from bokeh.models import Plot, Range1d, MultiLine, Circle, HoverTool, BoxZoomTool, ResetTool, PointDrawTool
from bokeh.models.graphs import from_networkx
from bokeh.palettes import Spectral4

import bokeh.plotting as bpl

bpl.output_notebook()

# Prepare Data
G = nx.karate_club_graph()

SAME_CLUB_COLOR, DIFFERENT_CLUB_COLOR = "black", "red"
edge_attrs = {}

for start_node, end_node, _ in G.edges(data=True):
  edge_color = SAME_CLUB_COLOR if G.nodes[start_node]["club"] == G.nodes[end_node]["club"] else DIFFERENT_CLUB_COLOR
  edge_attrs[(start_node, end_node)] = edge_color

nx.set_edge_attributes(G, edge_attrs, "edge_color")

# Show with Bokeh
plot = Plot(plot_width=400, plot_height=400,
          x_range=Range1d(-1.1, 1.1), y_range=Range1d(-1.1, 1.1))
plot.title.text = "Graph Interaction Demonstration"

node_hover_tool = HoverTool(tooltips=[("index", "@index"), ("club", "@club")])

graph_renderer = from_networkx(G, nx.spring_layout, scale=1, center=(0, 0))

graph_renderer.node_renderer.glyph = Circle(size=15, fill_color=Spectral4[0])
graph_renderer.edge_renderer.glyph = MultiLine(line_color="edge_color", line_alpha=0.8, line_width=1)

plot.add_tools(node_hover_tool, BoxZoomTool(), ResetTool(), PointDrawTool(renderers = [graph_renderer.node_renderer], empty_value = 'black'))

plot.renderers.append(graph_renderer)

output_file("interactive_graphs.html")
show(plot)

Thanks.

Already discussed here.

[bryevdv]

cc @philippjfr any thoughts on this? Offhand I think the only way this makes sense is with an entirely new tool that understands graph renderers explicitly. While there is probably a fairly trivial change to make the existing tool "work" with node renderers, the that would only let people move nodes but leave edges are they are to start, which seems less than useful.

Edit: or alternatively the existing tool could be special cased to understand being passed a GraphRenderer (not one of the sub-renderers)

Also all this said I can't think of any way to make this work usefully with a non-default layout provider.

[p-himik]

A recent question about this functionality on SO: https://stackoverflow.com/q/62950074/564509

[philippjfr]

I think for the default LayoutProvider it probably wouldn't be too hard to support this but as you said for a StaticLayoutProvider I don't think there's anything sensible we can do. That said it may be nice to finally implement a BezierLayoutProvider or similar which is the main use case I've had to use a non-default layout provider.