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https://github.com/SwallowOS/xorg_lib_libxcb
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38 lines
2.1 KiB
Plaintext
38 lines
2.1 KiB
Plaintext
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There are a number of problematic special cases in XKB. The issues
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mentioned here are at most partly resolved.
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1. The are several XxxDoodad structures defined in xkb.xml. They are used
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in a few lists, but in a rather special way:
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The struct "CommonDoodad" is supposed to be a rather generic data type,
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combining the most basic Doodad fields that are common in all these structures.
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All Doodads are encapsulated in a union type simply called "Doodad".
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Now this union is used in subsequent list definitions, aiming at a kind of
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'polymorphism': From inspection of the protocol and Xlib, the Doodads are to
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be discriminated based on their type field.
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However the special meaning of the type field is not encoded in the protocol.
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Furthermore the TextDoodad and the LogoDoodad are variable size types due to
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some fields of type CountedString16, thereby turning the union into a
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possibly variable size type as well.
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However, for lists with variable size elements, special sizeof functions are
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required. These cannot be autogenerated as it cannot be referred which
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Doodad type to use for the union.
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Therefore, the Doodad type structures are unsupported at the moment.
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2. There are still some bugs in xkb.xml: Either certain fields are missing
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that are required by the protocol, or Xlib simply has another understanding
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of the protocol.
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3. The interface for accessors should be reviewed.
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4. Currently some bitcases carry 'name' attributes. These could be avoided if
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the data within would consist of a singe struct field only.
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5. switch could get a 'fixed_size' attribute, so when rewriting valueparam to switch,
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an uint32_t * pointer could be used instead of void *.
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6. The automatic inclusion of padding requires some complicated coding in the
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generator. This is errorprone and could be avoided if all padding is explicitly
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given in the protocol definition. For variable size fields that require padding,
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the pad tag could get a 'fieldref' attribute. That way padding could be handled
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a lot easier in the autogenerator. |