Switch SVG path parsing to fonttools

[gmischler]

e.g. Fixes #525

Checklist:

• The GitHub pipeline is OK (green),
  meaning that both pylint (static code analyzer) and black (code formatter) are happy with the changes of this PR.
• A unit test is covering the code added / modified by this PR
• This PR is ready to be merged
• [NA] In case of a new feature, docstrings have been added, with also some documentation in the docs/ folder
• A mention of the change is present in CHANGELOG.md

The nice part is that the new parser resolves everything to absolute coordinates, and it does so in a very simple and elegant way. For us this means that many class definitions dealing with relative movements have become redundant. After removing them, sgv.py is now significantly shorter.

At first, I couldn't get the "exponentated numbers" to parse correctly. Then I found that my copy of fonttools was slightly outdated, and they had just recently fixed a bug quite similar to our own #376. I have now pinned fonttools to the current release 4.37.2 or newer as well to make sure we have this fix available.

Previously, the "comma seperation" test converted "M0,1l2,3" into [M(0, 1), L2, 3)]. I don't think this was correct, since a relative line_to should end up at absolute (2,4). I didn't analyze if this was our own bug or one in "svg.path", but now it's gone anyway.

When a path gets closed with "Z/z", the fonttools parser adds an explicit extra "L" back to the start point. They may need this internally, but it has no purpose for us. I had to add methods to drawing._graphics_context() and drawing.PaintedPath() for removing the last element of a path again to eliminate this.

I had to replace a few of the reference PDFs. They all looked identical visually, but the new ones were consistently a bit smaller.

By submitting this pull request, I confirm that my contribution is made under the terms of the GNU LGPL 3.0 license.

[codecov]

Codecov Report

Base: 94.12% // Head: 93.94% // Decreases project coverage by -0.17% ⚠️

Coverage data is based on head (ef05f6c) compared to base (af12339).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head ef05f6c differs from pull request most recent head 75a6e13. Consider uploading reports for the commit 75a6e13 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #545      +/-   ##
==========================================
- Coverage   94.12%   93.94%   -0.18%     
==========================================
  Files          22       22              
  Lines        6225     5999     -226     
  Branches     1271     1213      -58     
==========================================
- Hits         5859     5636     -223     
+ Misses        191      189       -2     
+ Partials      175      174       -1     

Impacted Files	Coverage Δ
fpdf/drawing.py	92.43% <100.00%> (-0.57%)	⬇️
fpdf/svg.py	96.63% <100.00%> (+0.68%)	⬆️
fpdf/prefs.py	90.90% <0.00%> (-1.95%)	⬇️
fpdf/syntax.py	95.37% <0.00%> (-0.05%)	⬇️
fpdf/fpdf.py	92.59% <0.00%> (-0.02%)	⬇️
fpdf/sign.py	100.00% <0.00%> (ø)
fpdf/enums.py	100.00% <0.00%> (ø)
fpdf/__init__.py	100.00% <0.00%> (ø)

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[Lucas-C]

Good job!
Nice code shrinking here, thank you @gmischler!

By the way, don't hesitate to ping me by email whenever you want to get the role of a maintainer on this project, I still think fpdf2 would benefit from it and you clearly deserve it

[Lucas-C]

$ pylint fpdf test tutorial/tuto*.py
************* Module fpdf.svg
fpdf/svg.py:552:0: W0223: Method 'addComponent' is abstract in class 'AbstractPen' but is not overridden (abstract-method)
fpdf/svg.py:558:4: W0237: Parameter 'pt' has been renamed to 'end' in overridden 'PathPen.moveTo' method (arguments-renamed)
fpdf/svg.py:564:4: W0237: Parameter 'pt' has been renamed to 'end' in overridden 'PathPen.lineTo' method (arguments-renamed)
fpdf/svg.py:570:4: W0221: Number of parameters was 2 in 'AbstractPen.curveTo' and is now 4 in overridden 'PathPen.curveTo' method (arguments-differ)
fpdf/svg.py:570:4: W0221: Variadics removed in overridden 'PathPen.curveTo' method (arguments-differ)
fpdf/svg.py:583:4: W0221: Number of parameters was 2 in 'AbstractPen.qCurveTo' and is now 3 in overridden 'PathPen.qCurveTo' method (arguments-differ)
fpdf/svg.py:583:4: W0221: Variadics removed in overridden 'PathPen.qCurveTo' method (arguments-differ)

[Lucas-C]

To me, this looks ready to be merged 😊