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[otData] Fix DeltaValue repeat value #3758

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Merged
merged 2 commits into from
Feb 4, 2025
Merged

[otData] Fix DeltaValue repeat value #3758

merged 2 commits into from
Feb 4, 2025
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behdad
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@behdad behdad commented Jan 30, 2025

The "" marker is used when a custom converter expects a list. For DeltaValues, we expect a list as a single value, not a list to be enumerated in XML. So, None is appropriate here. Cryptic, I know...

Fixes #3757

@behdad
[otData] Fix DeltaValue repeat value
24eb3f7 
The "" marker is used when a custom converter expects a list.
For DeltaValues, we expect a list as a single value, not a list
to be enumerated in XML. So, None is appropriate here. Cryptic,
I know...

Fixes #3757
@behdad behdad mentioned this pull request Jan 30, 2025
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behdad commented Jan 30, 2025

Would be nice to add a test for this, but I don't have cycles for right now.

@behdad behdad requested a review from anthrotype January 30, 2025 13:54
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wow.. the DeltaValue's conv.repeat field has been an empty string for 23 years and nobody noticed? 🤔
Is it like nobody ever used it?

Just to confirm I understand, seeting it to None basically is to take the else branch of this if statement, in BaseTable.fromXML?

fonttools/Lib/fontTools/ttLib/tables/otBase.py

Lines 1148 to 1159 in b467579

value = conv.xmlRead(attrs, content, font)
# Some manually-written tables have a conv.repeat of ""
# to represent lists. Hence comparing to None here to
# allow those lists to be read correctly from XML.
if conv.repeat is not None:
seq = getattr(self, conv.name, None)
if seq is None:
seq = []
setattr(self, conv.name, seq)
seq.append(value)
else:
setattr(self, conv.name, value)

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behdad commented Jan 30, 2025

wow.. the DeltaValue's conv.repeat field has been an empty string for 23 years and nobody noticed? 🤔
Is it like nobody ever used it?

I probably broke it in 2013: 7d13030

But yeah, wow!

Just to confirm I understand, seeting it to None basically is to take the else branch of this if statement, in BaseTable.fromXML?

Correct.

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behdad commented Jan 30, 2025

In HarfBuzz-using systems we don't even bother delta-adjusting GPOS.

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I'll work on a test tomorrow

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behdad commented Jan 30, 2025

I probably broke it in 2013: 7d13030

Oh. Probably more recently: ec78b57

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behdad commented Jan 30, 2025

I probably broke it in 2013: 7d13030

Oh. Probably more recently: ec78b57

I just checked, and DeltaValues are the only suspect of breakage from my change. The rest are intentional I believe:


>>> from otData import otData 
>>> for name,attrs in otData:
...     for typ,attrName,repeat,aux,desc in attrs:
...         if not repeat and repeat is not None:
...             print(name, attrName)
...             
Device DeltaValue
VarIdxMap mapping
DeltaSetIndexMapFormat0 mapping
DeltaSetIndexMapFormat1 mapping
MultiVarData Item
AxisIndicesList Item
VarCompositeGlyphs VarCompositeGlyph

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behdad commented Feb 4, 2025

LGTM. THanks.

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I force-pushed so that the test now does a full roundtrip (XML->binary->XML)

@anthrotype anthrotype merged commit 307b312 into main Feb 4, 2025
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@anthrotype anthrotype deleted the DeltaValue branch February 4, 2025 10:44
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