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