Fixes markup [sup] followed by [sub] doesn't work (issue #8077)

[azinneck0485]

Made changes to markup.py to fix #8077

Fix was to add a condition wh < pph to the logic used to calculate script_pos for sub-/superscript in render_lines method. This means the "if condition" is only evaluated when nested, otherwise the "else condition" is evaluated and used in the calculation.

Tested with the following file, which builds on the test script in the original issue report:
Issue8077_test.zip

Output display, showing multiple variations of sub and sup, including nested conditions:

Please let me know if there are any other tests I should run (I did not see anything in the documentation), additional changes that need to be make, or if I should make the pull request against a different branch.
 

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• Unittests are included in PR.
• Properly documented, including versionadded, versionchanged as needed.

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[misl6]

Hi @azinneck0485 ,

The automated PEP8 check is failing, can you take care of it?

[azinneck0485]

I fixed the places in markup.py where the changes I made failed the PEP8 check in my latest commit

[misl6]

LGTM. Thank you!

(merging the PR as-is, but if you want to add some tests and refactor that part to have a better readable code, no one will complain about it. 😅)

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