[Xcb] XKEYBOARD protocol definition

[Peter Harris]

Josh Triplett wrote:
> On Wed, Nov 11, 2009 at 04:41:06PM -0500, Peter Harris wrote:
>> Eamon Walsh wrote:
>>> Going off on a tangent here: if popcount goes in, then we don't need the
>>> <valueparam> element in the schema anymore.  The reason is that the
>>> following two snippets are identical:
>>>
>>> <valueparam value-mask-type="CARD32"
>>>             value-mask-name="value-mask"
>>>             value-list-name="value-list" />
>>>
>>> <field type="CARD32" name="value-mask" />
>>> <list name="value-list" type="CARD32">
>>>   <popcount><fieldref>value-mask</fieldref></popcount>
>>> </list>
> 
> Yes, *please*.  I'd love to see valueparam die in favor of something
> simpler and more general.
> 
>> All true. Even better would be to use
>> <switch>(<bitcase></bitcase)+</switch> to replace valueparam, to allow
>> generation of code that replaces xcb/util/aux.
> 
> Both seem useful, I think, depending on the situation.  If you truly
> just have a set of identical values and a bitmask indicating which ones
> you've supplied, a list with length given by a <popcount> seems perfect.

Agreed.

> If you want to supply slightly different values for different cases, or
> otherwise do anything out of the ordinary, <bitcase> seems preferable.
> 
> Can you give an example of replacing a standard <valueparam> with
> <bitcase>?

By using <bitcase>, you can vary the type of the data used. In a
hypothetical future server-side XCB, you could auto-generate boilerplate
that checks to make sure that CreateWindow/BorderPixmap is, in fact, a
valid Pixmap XID. This may also be useful for type-checking bindings
(perhaps Haskell - Antoine?).

For a slightly less hypothetical example, you can link the appropriate
enums to individual fields. This will let the Wireshark dissector
pretty-print RENDER/ChangePicture/repeat as "RepeatReflect" instead of
"3". Once I update the wireshark dissector generator, that is. (RENDER
example used instead of CreateWindow, since core X11 is still dissected
by the legacy X11 dissector in Wireshark.)

Peter Harris
-- 
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