84 lines
2.4 KiB
ReStructuredText
84 lines
2.4 KiB
ReStructuredText
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##########################
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Base table classes and API
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##########################
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.. contents:: On this page:
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:local:
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.. rubric:: Overview:
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:heading-level: 2
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The modules documented on this page are the base classes on which the
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:mod:`fontTools.ttLib` table converters are built. The
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:class:`.DefaultTable` is the most general; :class:`.asciiTable` is a
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simpler option for storing text-based data. For OpenType and TrueType
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fonts, the :class:`.otBase.BaseTTXConverter` leverages the model used
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by the majority of existing OpenType/TrueType converters.
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Contributing your own table convertors
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--------------------------------------
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To add support for a new font table that fontTools does not currently implement,
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you must subclass from :py:mod:`fontTools.ttLib.tables.DefaultTable.DefaultTable`.
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It provides some default behavior, as well as a constructor method (``__init__``)
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that you don't need to override.
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Your converter should minimally provide two methods::
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class table_F_O_O_(DefaultTable.DefaultTable): # converter for table 'FOO '
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def decompile(self, data, ttFont):
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# 'data' is the raw table data. Unpack it into a
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# Python data structure.
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# 'ttFont' is a ttLib.TTfile instance, enabling you to
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# refer to other tables. Do ***not*** keep a reference to
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# it: it will cause a circular reference (ttFont saves
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# a reference to us), and that means we'll be leaking
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# memory. If you need to use it in other methods, just
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# pass it around as a method argument.
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def compile(self, ttFont):
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# Return the raw data, as converted from the Python
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# data structure.
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# Again, 'ttFont' is there so you can access other tables.
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# Same warning applies.
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If you want to support TTX import/export as well, you need to provide two
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additional methods::
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def toXML(self, writer, ttFont):
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# XXX
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def fromXML(self, (name, attrs, content), ttFont):
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# XXX
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fontTools.ttLib.tables.DefaultTable
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-----------------------------------
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.. automodule:: fontTools.ttLib.tables.DefaultTable
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:members:
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:undoc-members:
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fontTools.ttLib.tables.asciiTable
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---------------------------------
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.. automodule:: fontTools.ttLib.tables.asciiTable
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:members:
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:undoc-members:
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fontTools.ttLib.tables.otBase
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-----------------------------
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.. automodule:: fontTools.ttLib.tables.otBase
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:members:
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:undoc-members:
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