[PATCH weston] hmi-controller: remove duplicate commit_changes in random mode

Pekka Paalanen ppaalanen at gmail.com
Mon Feb 8 09:20:50 UTC 2016

On Fri, 5 Feb 2016 21:42:02 +0000
"Ucan, Emre (ADITG/SW1)" <eucan at de.adit-jv.com> wrote:

> Hi Pekka,
> First Question:
> An ivi-layer should have properties so that a group of surfaces can
> be scaled and clipped according to destination and source rectangle
> of the layer.
> Second Question:
> We have requirements for compositing an ivi-surface on many layers
> and/or screens. But I think it is reasonable to restrict an ivi-layer
> to a single screen.

Hi Emre,

ok, and you are going to introduce ivi-view as a first-class concept in
the ivi_layout API?

Below are some things that came to my mind and they are only food for
thought, not requirements.

Do I understand the following right?

- created by Wayland clients (ivi apps) with a specific ivi-id
- has properties like size, but not position or src/dst rects
- what about opacity etc.? here or in ivi-view?
- may be associated with several ivi-views
- backed by a weston_surface

If opacity is not settable by the app, it would make more sense in

- is associated with exactly one ivi-surface
- created by the window manager system as a Weston/ivi-shell internal
- gets content from the ivi-surface
- links the ivi-surface to an ivi-layer
- property src rect given in ivi-surface coordinates
- property dst rect given in ivi-layer coordinate space
- backed by a weston_view

- groups ivi-views into an ordered set
- created by the window manager system as a Weston/ivi-shell internal
- links the set of ivi-views to exactly zero or one ivi-screen
- property src rect given in ivi-layer coordinate space
- property dst rect given in ivi-screen coordinate space
- IOW, maps content from ivi-layer space to ivi-screen space
- other properties like opacity? (note that correctly implementing
  opacity will have the same problem as sub-surfaces: you usually need
  an intermediate composite, which Weston does not implement atm.)
- may not be backed by any particular Weston core structure

- represents a single output (monitor)
- contents specified by multiple ordered ivi-layers
- no adjustable properties
- created by the window manager system as a Weston/ivi-shell internal
- 1:1 with a weston_output

In this scheme, you can place an ivi-surface on any ivi-layers at any
number of times by creating an ivi-view for each. The ivi-view
specifies the position, so each "clone" of the ivi-surface is
completely independently mappable.

Putting an ivi-layer on multiple ivi-screens can be implemented by
creating an ivi-layer per ivi-screen, and associating ivi-surfaces with
each ivi-layer by creating the necessary ivi-views.

About the ivi_layout API and its implementation:

I would recommend to have the API use pointers to struct ivi-surface,
ivi-view, etc. as the primary means of object reference, and leave the
ivi-id usage just for getting the pointer from an ivi-id and
functions creating objects. I think most of the API already is this
way, but the implementations are still matching a lot by ivi-id, when
they already have the pointer they are looking for.

The transition framework seems to be using a timer to get a callback
for advancing animations. Weston already has an animation framework,
but it is quite specific to weston_views and weston_spring, so I'm not
sure reusing that directly makes sense. However, what it does right is
hooking up to the output repaint cycle instead of using timers or idle
callbacks. This make sure that animation state is updated exactly the
right time, and not too late or too often.


> -----Original Message-----
> From: wayland-devel
> [mailto:wayland-devel-bounces at lists.freedesktop.org] On Behalf Of
> Pekka Paalanen Sent: Freitag, 5. Februar 2016 15:08 To: Ucan, Emre
> (ADITG/SW1) Cc: Nobuhiko Tanibata; securitycheck at denso.co.jp;
> Natsume, Wataru (ADITJ/SWG); wayland-devel at lists.freedesktop.org
> Subject: Re: [PATCH weston] hmi-controller: remove duplicate
> commit_changes in random mode
> On Thu, 4 Feb 2016 16:31:50 +0000
> "Ucan, Emre (ADITG/SW1)" <eucan at de.adit-jv.com> wrote:
> > Hi Pekka,
> > 
> > I am for removing the remaining bits of code which is wrongly
> > assuming that a surface can be shown in multiple layers.  
> Hi Emre,
> sounds good.
> >  Afterwards we have to redesign a big part of ivi_layout API to 
> > support this feauture.
> > 
> > My ideas for the redesign so far:
> > The most basic approach would be that an ivi_surface would have a 
> > weston_view for every layer/screen combination.  
> Yes, I believe that is how it could/should work.
> > But ivi_layout API
> > does not make much sense than. Because when controller calls 
> > ivi_layout_surface_set_destination_rectangle, should we scale all 
> > views ? I think it does not make sense to scale all views.  
> Indeed, that was a bit weird, like a surface's position on any layer
> being recorded with the surface, which means you cannot have
> per-layer positions. The same with layer vs. screen, IIRC.
> > Therefore,
> > the set APIs should be changed to get ivi_views and not
> > ivi_surfaces. This would mean:
> > 
> > - Modifying every ivi_layout_surface_set* API
> > - Implementing new APIs to get layer/screen specific ivi_views for
> > a given ivi_surface
> > - ivi-layers should list ivi_views and not ivi_surfaces
> > - The implementation of commit_changes should be updated
> > accordingly.
> > 
> > I am planning to do all these changes, but at first we can remove
> > old code. Because it is very unlikely that we can reuse.  
> Do you still think that ivi-layer should have a size and a position
> and all the other attributes? Or should it be used only for grouping
> and z-ordering ivi-surfaces/views, and linking them to a screen?
> Could an ivi-layer be on multiple screens? If you can restrict an
> ivi-layer to a single ivi-screen, I think that would simplify things
> a lot.
> It seems you are moving closer to weston's internal architecture with
> surfaces, views, and layers. :-)
> Thanks,
> pq
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