[PATCH videoproto] Xvproto: fix xvEncodingInfo to match actual wire protocol

[Daniel Martin]

On 9 June 2013 19:00, Julien Cristau <jcristau at debian.org> wrote:
> The padding is *before* the rate field, so the rate is placed on a 32bit
> boundary.  This change adds explicit padding between height and rate,
> and removes extraneous padding after the rate field, which the server
> never sent and xlib never read.
>
> This changes sizeof(xvEncodingInfo).  Hopefully that's not a big deal as
> clients only see the Xlib structure XvEncodingInfo.

(Hopefully, I'm right with that):
I think that's an ABI change and a bit more difficult. Think about an X
server, which is compiled against a xvproto version without that change
and the lib compiled against xvproto with that change. In that case the
lib would start to read the encoding info, where the X server just sended
those extraneous pad bytes.


I just saw that the reply structure itself (xvQueryEncodingsReply) has
such extraneous padding too:
  ...
  CARD32 length B32;
  CARD16 num_encodings B16;
  CARD32 padl3 B32;
  ...
And even without this padding sz_xvQueryEncodingsReply=32 is wrong,
as the fields sum up to 34 and with that padding we're at 36.

Cheers,
    Daniel Martin