[Xcb] Problem with xpyb and setCrtcConfig()

[Peter Harris]

Alberto Milone wrote:
> 
> Now it says that "SetCrtcConfig" takes exactly 10 arguments (9 given).
> 
> But I guess it should take 9 arguments:
> cookie = self.conn.randr.SetCrtcConfig(crtc.id, crtc.timestamp, 
> resources.config_timestamp, x, y, mode.id, rotation, map(lambda n: 
> n.id, outputs))

The C binding needs a length or count for the last parameter, since C
does not know how long a list is. I'm guessing (guessing, mind you,
since I don't actually know anything about the python binding) that the
python binding author decided to follow the XCB C binding implementation
as closely as possible, and you need to put in a redundant length or
count somewhere.

See also PolyPoint (and etc), as I mentioned previously.

> Also what's the function of padding bytes?

To allow the C binding (or Xlib before it) to cast a data buffer
directly to a structure.

http://en.wikipedia.org/wiki/Data_structure_alignment#Data_Structure_Padding

Peter Harris
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