Reencode() silently mis-encodes type1 fonts with Unused/detached glyphs

[HinTak]

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• The FontForge version and the operating system you're using

Based on source from git with hash: b8e5ff8, fedora linux, x86_64

• The behavior you expect to see, and the actual behavior

For example, for subfont 44, this is what ttf2tfm gives:

/a1sh44Encoding [
/index0x1AD1 /index0x1AD2 /index0x1AD3 /index0x1AD4
/index0x1AD5 /index0x1AD6 /index0x1AD7 /index0x1AD8
/index0x1ADA /index0x1ADB /index0x1ADC /index0x1ADD
/index0x1ADE /index0x1ADF /index0x1AE0 /index0x1AE1
/index0x1AE2 /index0x1AE3 /index0x1AE4 /index0x1AE5
/index0x1AE6 /index0x1AE7 /index0x1AE8 /index0x1AE9
/index0x1AEB /index0x1AEC /index0x1AED /index0x1AEE
/index0x1AF0 /index0x1AF1 /index0x1AF2 /index0x1AF3
...

This is what fontforge does (it is really glyph id rather than uniXXXX) - whenever fontforge seems to be randomly uses /uni44*, it encodes the wrong glyph. The glyph ids should be uni1AD1, etc. So half of subfont 44 is wrong, in my case.

/a1sh44-Enc [
/uni4400 /uni1AD2 /uni4402 /uni1AD4
/uni4404 /uni4405 /uni1AD7 /uni4407
/uni4408 /uni1ADB /uni1ADC /uni440B
/uni1ADE /uni1ADF /uni440E /uni1AE1
/uni1AE2 /uni4411 /uni4412 /uni1AE5
/uni4414 /uni1AE7 /uni1AE8 /uni4417
/uni4418 /uni1AEC /uni441A /uni441B
/uni1AF0 /uni441D /uni441E /uni1AF3
...

• [x ] Steps to reproduce the behavior

fontforge -script cjk/utils/subfonts/subfonts.pe SourceHanSerifTC_EL-M/SourceHanSerifTC
-Regular.otf a1sh /usr/share/texlive/texmf-dist/fonts/sfd/ttf2pk/Unicode.sfd

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• A description of the problem you're trying to solve, including why you think this is a problem
• If the feature changes current behavior, reasons why your solution is better
• (optional) Possible solution/fix/workaround

[HinTak]

I tried RemoveDetachedGlyphs(); No improvement.

[HinTak]

The problem was first noted on the CJK mailing list.

[HinTak]

The two contributing problems are #3084 and #3085 . That's all. I am able to workaround them with an external script, but it would be nice for both of them to be fixed properly.

[HinTak]

It would be nice if MultipleEncodingsToReferences() does the right thing - it currently does not.

[HinTak]

The fixed up freetype-py script is up at
https://github.com/HinTak/freetype-py/blob/fontval-diag/examples/subfonts-script-generate.py