crash with firefox logo on svglib 0.9.1, but works on 0.9.0

[Akuli]

Download https://upload.wikimedia.org/wikipedia/commons/6/67/Firefox_Logo%2C_2017.svg to firefox.svg

After pip install svglib==0.9.0 running this produces out.gif as expected, but after installing 0.9.1 it raises an error

from svglib import svglib
from reportlab.graphics.renderPM import drawToPIL, drawToFile

rlg = svglib.svg2rlg('firefox.svg')
drawToFile(rlg, 'out.gif')

Here is the error

Can't handle color: url(#radial-gradient)
Can't handle color: url(#radial-gradient-2)
Can't handle color: url(#linear-gradient)
Can't handle color: url(#radial-gradient-3)
Can't handle color: url(#radial-gradient-4)
Can't handle color: url(#radial-gradient-5)
Can't handle color: url(#radial-gradient-6)
Can't handle color: url(#radial-gradient-7)
Can't handle color: url(#linear-gradient-2)
Can't handle color: url(#linear-gradient-3)
Can't handle color: url(#linear-gradient-4)
Can't handle color: url(#linear-gradient-5)
Can't handle color: url(#linear-gradient-6)
Can't handle color: url(#linear-gradient-7)
Traceback (most recent call last):
  File "asdf.py", line 6, in <module>
    drawToFile(rlg, 'out.gif')
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderPM.py", line 680, in drawToFile
    c = drawToPMCanvas(d, dpi=dpi, bg=bg, configPIL=configPIL, showBoundary=showBoundary)
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderPM.py", line 666, in drawToPMCanvas
    draw(d, c, 0, 0, showBoundary=showBoundary)
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderPM.py", line 51, in draw
    R.draw(renderScaledDrawing(drawing), canvas, x, y, showBoundary=showBoundary)
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderbase.py", line 205, in draw
    self.drawNode(drawing)
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderPM.py", line 108, in drawNode
    self.drawNodeDispatcher(node)
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderbase.py", line 286, in drawNodeDispatcher
    self.drawGroup(node)
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderbase.py", line 317, in drawGroup
    self.drawNode(node)
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderPM.py", line 111, in drawNode
    self.pop()
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderPM.py", line 60, in pop
    self._tracker.pop()
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderbase.py", line 112, in pop
    reverseDelta[key] = inverse(lastDelta['transform'])
  File "/home/akuli/.local/lib/python3.5/site-packages/reportlab/graphics/renderbase.py", line 16, in inverse
    R = [A[3]/det, -A[1]/det, -A[2]/det, A[0]/det]
ZeroDivisionError: float division by zero

[claudep]

Thanks for the report, I'm almost certain the problem is in 918415335, where the condition if r != 0 is probably missing before the new introduced line. @ajbrock, maybe you could have a look?

[ajbrock]

I think I agree that adding if r!=0 before computing r = 1 / r -1 is a good idea to prevent divide by zero, but I'm not sure I see the error path that would lead to the divide-by-zero in reportlab. If the line in question were computing "1/0 -1" then wouldn't it be outputting an inf or a nan to reportlab? It looks like reportlab is dealing with a transform whose determinant is zero. I don't quite follow the trace logic from the ellipse code to reportlab though, so please feel free to enlighten me =)

[claudep]

Sorry for wrongly accusing the commit 9184153 for that regression. In fact, the problem arises after 82860fa54f8a2b.

[claudep]

@Akuli with 0.9.0 do you obtain anything else than a blank page?

[Akuli]

I seem to be getting blank page only with 0.9.0 so I think this is a good as it ever was, lol