Preserve format of value records after reading #861
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ValueRecords have an explicit format, which is generally stored once in their parent table. In the case of records with device or variation tables, we need to know the format in order to write them correctly, since it's possible for these fields to be legitimately null, and we cannot distinguish between a record which where a field is None because it is not included versus when it is intended to be null. Previously, we would use the format when reading the table but would then discard it. This led to a bug where we would not know the correct format when we went to write the table back. With this patch, we hold onto the format after reading, and pass it to write-fonts if we convert to write-fonts types. This ensures that we roundtrip tables correctly in this case.
anthrotype
approved these changes
Mar 26, 2024
rsheeter
reviewed
Mar 26, 2024
| pub fn read_old(data: &[u8], format: ValueFormat) -> Result<Self, ReadError> { | ||
| let data = FontData::new(data); | ||
| Self::read(data, format) | ||
| // we ignore the format for the purpose of equality testing, it's redundant |
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if it's redundant why do we need to store it? - seems slightly contradictory. Perhaps further explanation of how this makes sense?
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sorry, it is redundant for the purposes of comparing two value records. In that case (testing, e.g.) I don't think we care.
rsheeter
approved these changes
Mar 26, 2024
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ValueRecords have an explicit format, which is generally stored once in their parent table. In the case of records with device or variation tables, we need to know the format in order to write them correctly, since it's possible for these fields to be legitimately null, and we cannot distinguish between a record which where a field is None because it is not included versus when it is intended to be null.
Previously, we would use the format when reading the table but would then discard it. This led to a bug where we would not know the correct format when we went to write the table back.
With this patch, we hold onto the format after reading, and pass it to write-fonts if we convert to write-fonts types. This ensures that we roundtrip tables correctly in this case.
closes #858