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API Notes for the CoreGraphics bindings
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Introduction
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This document describes special considerations for the PyObjC based CoreGraphics
bindings.

Callbacks
---------

The ``userinfo`` for ``CGDataConsumerCreate``, ``CGDataProviderCreate``,
``CGDataProviderCreateDirect``, ``CGDataProviderCreateDirectAccess``,
``CGDataProviderCreateSequential``, ``CGDataProviderCreateWithData``,
``CGDisplayRegisterReconfigurationCallback``, 
``CGDisplayRemoveReconfigurationCallback``, 
``CGFunctionCreate``, ``CGRegisterScreenRefreshCallback``, 
``CGReleaseScreenRefreshRects``, ``CGScreenRegisterMoveCallback``,
``CGScreenUnregisterMoveCallback``, ``CGUnregisterScreenRefreshCallback``,
``CGPDFDictionaryApplyFunction``, ``CGPathApply``, ``CGPatternCreate``,
``CGEventTapCreate``, ``CGEventTapCreateForPSN``, ``CGPDFOperatorTableSetCallback`` and ``CGPSConverterCreate``  can be any Python object.

The function arguments for these functions can be any Python callable, 
including bound methods. Functions mentioned earlier that have a struct with
callback functions take in tuple with those callbacks in Python.

``CGEventTapCreate`` and ``CGEventTapCreateForPSN`` leak some memory when they
are called. This is needed to avoid memory management problems. It is therefore
advisable not to call these functions, are at least call them a small number
of times.

``CGPDFOperatorTableSetCallback`` is not supported at the moment.