SVG canvas scaling and .replace method

[hyanwong]

A few times now, myself and others (e.g. @gtsambos) have wanted to make the SVG canvas a little bigger, e.g. to accommodate long or rotated labels, etc.

There's a quick hack to do this as follows:

import tskit
from IPython.display import display, SVG
w = 300
h = 200
tree = tskit.Tree.generate_balanced(10)
svg = tree.draw_svg(
    size=(w, h),
    style=".leaf > .lab {text-anchor: start; transform: rotate(90deg) translate(6px)}",
    node_labels={u: "abcedfghij"[u] * 10 for u in ts.samples()},
)
display(svg) # labels cut off

# Hack to make room for labels
taller_svg = svg.replace(f'height="{h}"', f'height="{h+50}"', 1)
display(SVG(taller_svg))

So two things here:

1. should we implement the .replace method on the tskit.SVGstring class, so ti returns another SVGstring? That would save a small amount of hassle, but I don't want to be implementing all the other standard string methods that return a string. I guess this would be just

   def replace(self, *args, **kwargs):
       return tskit.SVGString(self.replace(*args, **kwargs))
   

2. should we be able to specify a different canvas size from the size() passed to draw_svg to avoid having to hack it altogether?

[jeromekelleher]

Adding a canvas_size to draw_svg seems a reasonable thing to do - a lot of this layout stuff is pretty arbitrary so adding options to tweak is good.

[hyanwong]

SGTM