[Telepathy] Gabble avatars: requirements

[Simon McVittie]

On Sun, 15 Oct 2006 at 03:47:07 +0100, Dafydd Harries wrote:
>  - GetAvatarRequirements() -> ([], 0, 0, 0, 0 ,0)
> 
>    I.e. Jabber doesn't specify mime types or min/max dimensions or max size,
>    as far as I know. The avatars spec doesn't actually say what the CM should
>    do if there are no requirements specified by the protocol.

XEP-0153 specifies:

- image SHOULD be <= 8192 bytes, enforced by the publishing client
- support for image/png is REQUIRED, for image/gif and image/jpeg is
  RECOMMENDED, for any other type is OPTIONAL
- size SHOULD be 32 <= size <= 96 px in each direction, 64px is RECOMMENDED
- image SHOULD be square

which isn't something we can express in the current avatar interface. My
inclination would be to have Gabble advertise stricter requirements on
the D-Bus:

GetAvatarRequirements() -> (['image/png', 'image/jpeg', 'image/gif'],
                            32, 96, 32, 96, 8192)

although it may be better to accept non-conforming avatars even though
our reply to GetAvatarRequirements() claims we won't.

It may be worth looking at other avatar-supporting clients to
find out what current practice is (since scaling small bitmaps leads to
unpleasant-looking UIs).

Looking at related XEPs which we currently have no plans to support:
XEP-0084 (publish/subscribe avatars) makes the same suggestions as XEP-0153,
but additionally requires that the avatar must be available as image/png
(as one of, potentially, many alternatives). XEP-0008 has been deferred -
it's basically XEP-0153 but using a dedicated iq for avatar retrieval
instead of sharing the vCard.

	Simon