[Xcb] using enums as type in sync.xml

[Jeremy A. Kolb]

I know that DirectX does does something like: FORCE_SIZE = 0xffffffff as 
the last item in an enum to force an enum to 32bits.  Would something like 
this work?

Jeremy

On Thu, 6 Sep 2007, Ian Osgood wrote:

> 
> On Sep 5, 2007, at 8:56 AM, Thomas Hunger wrote:
> 
> > Hello,
> >
> > sync.xml uses enums as types. This is readable, but a problem because
> >
> > 1) enums can have different binary sizes on different
> >    platforms and depending on the range they cover.
> >
> > 2) The size required in the X protocoll might not be the same
> >    as the native platform enum size (this is very prominent in
> >    XKB which uses 1, 2 and 4 byte enumerations in X).
> >
> >   <struct name="TRIGGER">
> >     <field type="COUNTER" name="counter" />
> >     <field type="VALUETYPE" name="wait_type" />
> >     <field type="INT64" name="wait_value" />
> >     <field type="TESTTYPE" name="test_type" />
> >   </struct>
> >
> > An easy workaround is to define
> >
> >   <typedef newname="VALUETYPE" oldname="CARD32"/>
> >   <typedef newname="TESTTYPE" oldname="CARD32"/>
> >
> > A patch is attached.
> >
> > tom
> > <0001-Let-types-point-to-typedefs-instead-of-enums-to-ensu.patch>
> 
> Comments:
> 
>  > +  <enum name="ALARMSTATE_ENUM">
> 
> I don't like this naming convention.
> 
> My recommendation:
> 
> In other requests, we replaced the enum typename in the request with  
> the cardinal of the appropriate size, in this case:
> 
> -     <field type="VALUETYPE" name="wait_type" />
> +     <field type="CARD32" name="wait_type" />  <!-- enum VALUETYPE -->
>        <field type="INT64" name="wait_value" />
> -     <field type="TESTTYPE" name="test_type" />
> +     <field type="CARD32" name="test_type" />   <!-- enum TESTTYPE -->
> 
> This is not ideal for language bindings other than C, because we are  
> losing type information. We have discussed in the past enhancing our  
> <field> description to take both an optional size and a type in order  
> to handle this problem. (We can't give the enum a size because it may  
> be reused in different requests for fields with differing sizes.)
> 
> (Another option is to define a union type for these fields. The union  
> for the wait_type field would expand to:
> union {
>    uint32 space;
>    enum XCB_VALUETYPE_T e;
> } xcb_wait_field_t ;
> but this might run into MSB/LSB portability problems.)
> 
> Ian
> 
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