On 30/09/15 11:37 AM, Bill Spitzak wrote:
>
>
> On Wed, Sep 30, 2015 at 8:59 AM, Derek Foreman <der...@osg.samsung.com
> <mailto:der...@osg.samsung.com>> wrote:
>
> Having an invalid serial number is quite useful - for example, we can
> have protocol requests that optionally take a serial number or 0
> instead of having two similar requests.
>
> Signed-off-by: Derek Foreman <der...@osg.samsung.com
> <mailto:der...@osg.samsung.com>>
> ---
>
> Well, let's see where this goes ;)
>
>
> I certainly hope this sort of thing is accepted.
There was some discussion about it on irc back in February, seemed to be
at least a little interest.
> I do wonder if we should have a wl_serial_compare() as part of wayland
> but the semantics are tricky (a big serial and a small serial may
> actually
> have happened quite close to eachother if the small happened after a
> wrap around).
>
>
> Just let the programmers use signed arithmetic. There is no reason to
> make this too complicated. If SIGNED_SERIAL_T is the signed equivalent
> to the serial number, then the following will detect if a is before b:
>
> SIGNED_SERIAL_T(a-b) < 0
>
> This sets the "arbitrary distance" to 1/2 the entire serial space.
So you're in favour of not bothering to give a helper function in
libwayland, and just expecting everyone to do their own thing?
Sounds good to me, I'll tally votes before I waste any time writing a
helper then. :)
> --- a/src/wayland-server.c
> +++ b/src/wayland-server.c
> @@ -826,7 +826,7 @@ wl_display_create(void)
> wl_signal_init(&display->destroy_signal);
>
> display->id = 1;
> - display->serial = 0;
> + display->serial = 1;
>
> wl_array_init(&display->additional_shm_formats);
>
> @@ -979,6 +979,9 @@ wl_display_next_serial(struct wl_display *display)
> {
> display->serial++;
>
> + if (display->serial == 0)
> + display->serial++;
> +
> return display->serial;
> }
>
>
> I suspect this causes the first event to have a serial number of 2, not
> 1. Not a big deal, but it might be better to initialize the serial
> number to zero, or you can initialize it to -1 if you want the structure
> to always have a valid serial number.
>
It's possible, I think, to call wl_display_get_serial() without ever
having called wl_display_next_serial() - not sure whether that's
considered valid or not.
So I figured I'd take a chance at throwing away 1 of the billions in
order to not have to worry about that.
Thanks for taking a look.
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