[PATCH] Xi: check all handlers before applying property changes.

[Simon Thum]

Peter Hutterer wrote:
> The current code exposes to inconsistent updates, i.e. if handler N succeeds
> but handler N+1 fails in setting the property, an error is returned to the
> client although parts of the server now behave as if the property change
> succeeded.
I understand the problem, but are there really uses for this? I mean, 2
handlers responding to the same prop is nothing I could make sense of.
At most, an additional handler which 'watches' the prop this way is
conceivable to me.

> This patch adds a "checkonly" parameter to the SetProperty handler. The
> handlers are then called twice, once with checkonly set to TRUE.
> On the checkonly run, handlers _MUST_ return error codes if the property
> cannot be applied. Handlers are not permitted to actually apply the changes.
> On the second run, handlers are permitted to apply property changes.
> Errors codes returned on the second run are ignored.
Things could be simpler IMO when having different return codes for 'I
don't care' vs. 'Yep, property properly changed'. I think that's the
root of the problem.

Fixing that would make it possible to discourage 'double' handlers by
traversing handlers only until one succeeds.

If that's a design goal, however, simply ignore me.

Cheers,

Simon