Improve performance working with unicode fonts (#907)

[andersonhc]

I am doing some tests using functools cache to improve performance working with unicode fonts.

test_cell/test_cell_speed_with_long_text is running 50% faster.

I will do additional tests soon.

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

• 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

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

[gmischler]

This is an very interesting approach.

We should probably test this with some longish text in chinese/japanese, or with a multilingual font. I suspect that a cache size of 128 is far too small in those cases (and I don't think increasing it will hurt anything with smaller alphabets).

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.28%. Comparing base (a313586) to head (ae21192).
Report is 8 commits behind head on master.

❗ Current head ae21192 differs from pull request most recent head 335c4e7. Consider uploading reports for the commit 335c4e7 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1158      +/-   ##
==========================================
+ Coverage   93.27%   93.28%   +0.01%     
==========================================
  Files          30       30              
  Lines        9228     9250      +22     
  Branches     2103     2105       +2     
==========================================
+ Hits         8607     8629      +22     
- Misses        379      382       +3     
+ Partials      242      239       -3     

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[Lucas-C]

test_cell/test_cell_speed_with_long_text is running 50% faster.

Wow, that is quite an improvement!
Good job @andersonhc!
This is very promising 🙂