[PATCH weston v5 16/36] libweston: add weston_head_is_device_changed() API

[Pekka Paalanen]

On Fri, 2 Feb 2018 16:25:56 -0600
Derek Foreman <derekf at osg.samsung.com> wrote:

> On 2017-12-14 05:40 AM, Pekka Paalanen wrote:
> > From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> > 
> > Reacting to DRM hotplug events is racy. It is theoretically possible to
> > get hotplug events for a quick swap from one monitor to another and
> > process both only after the new monitor is connected. Hence it is
> > possible for display device information to change without going through
> > a disconnected state for the head.  
> 
> I figured you'd have to address this somewhere. :)
> 
> > To support such cases, add API to allow detecting it in the compositor.
> > 
> > Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> > ---
> >   libweston/compositor.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++----
> >   libweston/compositor.h |  7 ++++
> >   2 files changed, 89 insertions(+), 6 deletions(-)
> > 
> > diff --git a/libweston/compositor.c b/libweston/compositor.c
> > index 86efcfad..0d3e185b 100644
> > --- a/libweston/compositor.c
> > +++ b/libweston/compositor.c
> > @@ -4714,6 +4714,31 @@ weston_head_release(struct weston_head *head)
> >   	wl_list_remove(&head->compositor_link);
> >   }
> >   
> > +static void
> > +weston_head_condition_device_changed(struct weston_head *head, bool condition)
> > +{
> > +	if (!condition)
> > +		return;  
> 
> It feels odd to me to check the condition here instead of having the 
> callers do something like:
> if (condition) weston_head_device_changed();

Yeah, it could certainly be done that way. ISTR to go through various
variations, but not sure I tried exactly that though. The starting point
was how weston_head_set_connection_status() was.

I could change that.

> But I guess that's a style thing, so my personal preference doesn't hold 
> much weight here...
> 
> Either way,
> Reviewed-by: Derek Foreman <derekf at osg.samsung.com>


Thanks,
pq


> > +
> > +	head->device_changed = true;
> > +
> > +	if (head->compositor)
> > +		weston_compositor_schedule_heads_changed(head->compositor);
> > +}
> > +
> > +/** String non-equal comparison with NULLs being equal */
> > +static bool
> > +str_null_neq(const char *a, const char *b)
> > +{
> > +	if (!a && !b)
> > +		return false;
> > +
> > +	if (!!a != !!b)
> > +		return true;
> > +
> > +	return strcmp(a, b);
> > +}
> > +
> >   /** Store monitor make, model and serial number
> >    *
> >    * \param head The head to modify.
> > @@ -4724,6 +4749,8 @@ weston_head_release(struct weston_head *head)
> >    * \param serialno The monitor serial number, a made-up string, or NULL for
> >    * none.
> >    *
> > + * This may set the device_changed flag.
> > + *
> >    * \memberof weston_head
> >    * \internal
> >    */
> > @@ -4733,6 +4760,11 @@ weston_head_set_monitor_strings(struct weston_head *head,
> >   				const char *model,
> >   				const char *serialno)
> >   {
> > +	weston_head_condition_device_changed(head,
> > +				str_null_neq(head->make, make) ||
> > +				str_null_neq(head->model, model) ||
> > +				str_null_neq(head->serial_number, serialno));
> > +
> >   	free(head->make);
> >   	free(head->model);
> >   	free(head->serial_number);
> > @@ -4748,6 +4780,8 @@ weston_head_set_monitor_strings(struct weston_head *head,
> >    * \param mm_width Image area width in millimeters.
> >    * \param mm_height Image area height in millimeters.
> >    *
> > + * This may set the device_changed flag.
> > + *
> >    * \memberof weston_head
> >    * \internal
> >    */
> > @@ -4755,6 +4789,10 @@ WL_EXPORT void
> >   weston_head_set_physical_size(struct weston_head *head,
> >   			      int32_t mm_width, int32_t mm_height)
> >   {
> > +	weston_head_condition_device_changed(head,
> > +					     head->mm_width != mm_width ||
> > +					     head->mm_height != mm_height);
> > +
> >   	head->mm_width = mm_width;
> >   	head->mm_height = mm_height;
> >   }
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