8000 MarkFeatureWriter does not allow multiple anchor marks on the same glyph · Issue #303 · googlefonts/ufo2ft · GitHub
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MarkFeatureWriter does not allow multiple anchor marks on the same glyph #303

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khaledhosny opened this issue Dec 21, 2018 · 10 comments · Fixed by #416
Closed

MarkFeatureWriter does not allow multiple anchor marks on the same glyph #303

khaledhosny opened this issue Dec 21, 2018 · 10 comments · Fixed by #416

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@khaledhosny
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I believe this is a regression, since my font used to build fine with fontmake 1.4.0 (not sure what version of ufo2ft this used).

If a glyph has more than one mark anchor, e.g. _mark1 and _mark2 only one of them will end up in the generated mark classes. This is caused by the code in: https://github.com/googlei18n/ufo2ft/blob/39ab30c54ab71b24d96bb68e0965c41937d39b35/Lib/ufo2ft/featureWriters/markFeatureWriter.py#L361-L364

I don’t know what the rationale for this, but it is a severe limitation and breaks my fonts. OpenType allows any number of mark anchors on a glyphs and ufo2ft should allow this.

For testing, try building Reem Kufi with latest fontmake and ufo2ft, the string لأ should render like the first image below, but it now renders like the second:
o n
@khaledhosny khaledhosny changed the title MarkFeatureWriter does nlt allow multiple anchor marks on the same glyph MarkFeatureWriter does not allow multiple anchor marks on the same glyph Jan 2, 2019
@anthrotype
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anthrotype commented Mar 1, 2019 •
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The change was meant to match Glyphs.app behavior. The problem with multiple mark anchors on the same glyph is that the same glyph cannot belong to multiple mark classes within the same lookup subtable, and unlike before when we were creating one mark2base lookup for each markClass (thus they were always disjoint and the problem didn’t arise), we now make a single mark2base lookup.

@moyogo
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moyogo commented Mar 1, 2019

About that... Null anchors are read as anchors at (0, 0) by InDesign 14.0.1 and maybe others. We didn’t have this issue with split lookups.

@moyogo
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moyogo commented Mar 1, 2019

I don’t think we should match Glyphs.app here, or at least one should have the option not to.
If one diacritic has more than one mark anchor then the mark2base lookup should be split to preserve the anchors in the source files.

@anthrotype
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Sounds reasonable. I won’t be able to look into it before second week of March. But I’d happily review PR

@madig
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madig commented Mar 3, 2019 •
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@schriftgestalt: How does Glyphs handle this case?

@schriftgestalt
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I don’t think Glyphs can handle multiple _mark anchors. Just to be sure, I can’t find the test font in the linked repo?

@khaledhosny
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I don’t think Glyphs can handle multiple _mark anchors. Just to be sure, I can’t find the test font in the linked repo?

There is both UFO sources and generated OTFs in the repo.

khaledhosny added a commit to aliftype/reem-kufi that referenced this issue Apr 7, 2019
@khaledhosny
Pin the last working version of ufo2ft
ea8ca47 
Together with the last version of fontmake that can work with it.
googlefonts/ufo2ft#303
khaledhosny added a commit to aliftype/reem-kufi that referenced this issue May 6, 2019
@khaledhosny
Add own mark feature writer
9d2c70e 
Copied from ufo2ft commit 3fe4446ec60231baf5bc5f9992bf99feb0be2f92, as
later ones are broken: googlefonts/ufo2ft#303

This allows us to use the latest fontmake again.
khaledhosny added a commit to aliftype/mada that referenced this issue May 6, 2019
@khaledhosny
Add own mark feature writer
80048e9 
Copied from ufo2ft commit 3fe4446ec60231baf5bc5f9992bf99feb0be2f92, as
later ones are broken: googlefonts/ufo2ft#303

This allows us to use the latest fontmake again.
@justvanrossum justvanrossum mentioned this issue May 6, 2019
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@anthrotype anthrotype mentioned this issue Jun 26, 2019
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anthrotype added a commit that referenced this issue Jun 26, 2019
@anthrotype
Revert "markFeatureWriter: sort anchors alphabetically in _groupMarkG…
0b29744 
…lyphsByAnchor"

This reverts commit 7e28c50.

Probably not such a good idea actually. Using the existing anchors order
allows user to determine which anchor is selected as the "first"
anchor (i.e. the one that assigns a mark glyph to its unique markClass).

See #303 and #336
@anthrotype
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I have a patch locally that uses fontTools.misc.classifyTools.Classifier to make disjoint sets of markClasses which I then use to build multiple lookup subtables to ensure that mark classes do not intersect. Unfortunately it isn't ready to push and am going on vacation tomorrow. I will continue work on this when I am back in mid July.

@moyogo
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moyogo commented Nov 21, 2019

@anthrotype What’s the status of your patch? We can work on it if you share the branch?

@anthrotype
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@moyogo sorry I can't seem to find it any more... Do you want to take this up?

@belluzj belluzj mentioned this issue Oct 30, 2020
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Allow multiple anchor classes per mark glyph in the mark feature daltonmaag/ufo2ft
5 participants
@khaledhosny @schriftgestalt @madig @moyogo @anthrotype
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