38 lines
1.6 KiB
Python
38 lines
1.6 KiB
Python
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"""fontTools.ttLib.tables.otDataSchema -- contains the FieldSpec dataclass, which is
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used to define the schema of OpenType tables in otData.py.
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"""
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from typing import Any, NamedTuple
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class FieldSpec(NamedTuple):
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"""Represents a single field in an OpenType table schema.
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These are defined in `otData.py` and used to construct converters in
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`otConverters.py`.
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Attributes:
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type: The type of the field. This string is used by `otConverters.py` to
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select or construct the appropriate converter. It can be a simple
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type name (e.g. 'uint16', 'Tag', 'Offset'), a specialized type (e.g.
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'ValueRecord', 'DeltaValue'), or a more complex expression (e.g.
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'OffsetTo(AatStateTable)', 'AATLookup(UShort)') which is evaluated
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to create a converter factory.
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name: The name of the field as defined in the OpenType specification.
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repeat: If the field is an array, this defines how many times it
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repeats. It can be an integer, or the name of another field (usually
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a 'Count' field) that contains the number of repetitions. If it is a
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string, it is used to lookup the count value from the table.
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aux: Auxiliary data used by some converters. When `repeat` is not set
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and `aux` is a string, it is often compiled into a Python
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expression for evaluation. For repeating structs, it is often used
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as a constant or an expression.
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description: A human-readable description of the field's purpose.
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"""
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type: str
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name: str
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repeat: Any = None
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aux: Any = None
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description: str = ""
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