[Xcb] xinput2 - request for help and comments

[Daniel Martin]

Hi everyone,

I'm working on bringing xinput2 support to xcb and I need a helping hand
and one or the other suggestion.

Lots of things are straight forward, but the reply of the QueryDevice
request is very complex and can't be processed with the current
implementation of xcbgen.

QueryDevice in the spec:
http://cgit.freedesktop.org/xorg/proto/inputproto/tree/specs/XI2proto.txt#n684

Besides a CARD16, this reply contains a LISTofDEVICEINFO, which contains
a LISTofCLASS. Each CLASS can be of a different type with a different
(even variable) length.

To give you a hint on what I think the xml implementation should look
like, I've prepared and attached a stripped to the bones examples.
Summary for this example:
- the reply has a "list of DeviceInfo structs"
- a DeviceInfo struct has a "list of ClassInfo structs"
- a ClassInfo struct has the default header (type, length, sourceid) and
  a switch for the different types to represent their details

That switch inside of the struct can't be handled atm. and xcbgen
complains about it with:
    Traceback (most recent call last):
      File "./c_client.py", line 2925, in <module>
        module.generate()
      File "8< to long 8< /state.py", line 101, in generate
        item.out(name)
      File "./c_client.py", line 1818, in c_struct
        _c_iterator(self, name)
      File "./c_client.py", line 1333, in _c_iterator
        _c('    xcb_generic_iterator_t child = %s;', \
                _c_iterator_get_end(self.last_varsized_field, 'R'))
      File "./c_client.py", line 1270, in _c_iterator_get_end
        return _c_iterator_get_end(field.type.last_varsized_field, accum)
    AttributeError: 'SwitchType' object has no attribute \
        'last_varsized_field'

Additionally, I've added a <case> element into the schema, patch is
attached as well. Haven't made it a "real git" patch, cause it's a rfc.
The (class) types (Key=0, Button=1, Valuator=2, Scroll=3, Touch=8) are
constants, not bitfields, so this might be necessary.

I've already had a working example without such a switch. But, in that
example one would have had to walk through the LISTofDEVICEINFO and
LISTofCLASS by hand and that's definitly something for an iterator.

I appreciate any suggestions, much more if it simplifies something. Or
if you're more skilled in Python than I'm, which is not difficult, and
could try to enhance xcbgen the way which is necessary to solve this
issue, that would be fantastic, too.

Thanks to Peter Harris and Peter Hutterer who answered my questions so
far.


Cheers,
    Daniel Martin
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diff --git a/src/xcb.xsd b/src/xcb.xsd
index cfa90c9..fa584d8 100644
--- a/src/xcb.xsd
+++ b/src/xcb.xsd
@@ -74,9 +74,11 @@ authorization from the authors.
     <xsd:sequence>
       <!-- switch(expression) -->
       <xsd:group ref="expression" minOccurs="1" maxOccurs="1" />
-      <xsd:choice>
+      <xsd:choice minOccurs="1" maxOccurs="unbounded">
         <!-- bitcase expression - bit test -->
-        <xsd:element name="bitcase" type="caseexpr" minOccurs="1" maxOccurs="unbounded" />
+        <xsd:element name="bitcase" type="caseexpr" minOccurs="0" maxOccurs="unbounded" />
+        <!-- case expression - value/constant test -->
+        <xsd:element name="case" type="caseexpr" minOccurs="0" maxOccurs="unbounded" />
       </xsd:choice>
       <!-- default: -->
       <xsd:group ref="fields" minOccurs="0" maxOccurs="1" />
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