Added interpolation of glyph advance width, from HVAR/hmtx, and derivation of new LSB.
Updated tests to match.
Needed to cherrypick from another branch an update for psCharstrings to allow the CFFSubr.draw() method to work.
varStore.py. Commit the correct function references.
psCharstrings.py. Add decompiler class specifically for flattening subroutinized charstrings.
mutator.py. Flatten the subroutinized charstrings, delete the Subrs.
TestCFF2VF.otf, Updated to version with subroutinization. Updated expected ttx output.
varLib.py. restore import of 'fontTools.misc.py23 import *'
varStore.py. Rename 'applyScalar' to 'interpolateFromDeltasAndScalars', and refactor common code with __git__item to a static method.
mutator.py. Update to reflect function name change to interpolateFromDeltasAndScalars. Changed some logic from one line to several lines for readability, and i to avoid flake8 warnings about line too long.
See 0283b1f.
By finishing overlayBox() to cull remainder box when possible, we generate
far fewer spurious boxes, if any.
For the featureVars_test.py test case, this now generates optimal output,
that is, 2*n - 1 boxes.
Running time for n=20 stays at 0.06s, which is probably Python startup
time.
Running time for n=100 is down from 2.5s with unoptimized new algorithm,
to 0.17s for this and number of output boxes from 5050 to the optimal 199.
Fixes#1372 again
Whereas previous algorithm had exponential running time and return
value size, new one has quadratic.
For featureVars_test.py test case, for example, which is a pathological
test case of n sliding intervals, the number of output intervals of
various algorithms are:
- Previous algorithm: 2**n - 1
- New algorithm: n*(n-1)/2
- Optimal algorithm: 2*n - 1
Ie, we go from exponential to quadratic, whereas in this case the optimal
solution is linear.
Running time of said test, for n=20, goes from over 20s, to 0.06s.
The algorithm can be improved. The overlayBox() function currently does
not try to shrink the remainder box. Doing that will probably bring us
to optimal solution for this test case.
Fixes https://github.com/fonttools/fonttools/pull/1372
One test is failing. Needs to be investigated that new output is correct,
and test expectations updated.
