[PATCH weston-ivi-shell v5 6/9] A reference implementation of UI client how to use ivi-hmi-controller.

[Pekka Paalanen]

On Tue, 20 May 2014 19:02:56 +0900
Nobuhiko Tanibata <nobuhiko_tanibata at xddp.denso.co.jp> wrote:

> 2014-04-25 20:55 に Pekka Paalanen さんは書きました:
> > On Thu, 20 Mar 2014 16:00:57 +0900
> > Nobuhiko Tanibata <NOBUHIKO_TANIBATA at xddp.denso.co.jp> wrote:
> > 
> >> This is launched from hmi-controller by using hmi_client_start and 
> >> create a
> >> pthread.
> >> 
> >> The basic flow is as followed,
> >> 1/ create pthread
> >> 2/ read configuration from weston.ini.
> >> 3/ draw png file to surface according to configuration of weston.ini
> >> 4/ set up UI by using ivi-hmi-controller protocol
> >> 5/ Enter event loop
> >> 6/ If a surface receives touch/pointer event, followings are invoked 
> >> according
> >>    to type of event and surface
> >> 6-1/ If a surface to launch ivi_application receive touch up, it execs
> >>      ivi-application configured in weston.ini.
> >> 6-2/ If a surface to switch layout mode receive touch up, it sends a 
> >> request,
> >>      ivi_hmi_controller_switch_mode, to hmi-controller.
> >> 6-3/ If a surface to show workspace having launchers, it sends a 
> >> request,
> >>      ivi_hmi_controller_home, to hmi-controller.
> >> 6-4/ If touch down events happens in workspace,
> >>      ivi_hmi_controller_workspace_control is sent to slide workspace.
> >>      When control finished, event: 
> >> ivi_hmi_controller_workspace_end_control
> >>      is received.
> >> 
> >> Signed-off-by: Nobuhiko Tanibata <NOBUHIKO_TANIBATA at xddp.denso.co.jp>
> >> ---
> >> 
> >> Changes for v2:
> >>  - squash Makefile to this patch
> >> 
> >> Changes for v3 and v4:
> >>  - nothing. Version number aligned to the first patch
> >> 
> >> Changes for v5:
> >>  - usleep with roundtrip uses CPU. replace them with 
> >> wl_display_dispatch
> >> 
> >>  ivi-shell/Makefile.am                 |    2 +
> >>  ivi-shell/hmi-controller-homescreen.c | 1369 
> >> +++++++++++++++++++++++++++++++++
> >>  ivi-shell/hmi-controller-homescreen.h |   36 +
> >>  ivi-shell/hmi-controller.c            |    3 +-
> >>  4 files changed, 1409 insertions(+), 1 deletion(-)
> >>  create mode 100644 ivi-shell/hmi-controller-homescreen.c
> >>  create mode 100644 ivi-shell/hmi-controller-homescreen.h
> > 
> > Would it not be simpler and more robust to make this an independent
> > program like e.g. clients/desktop-shell.c is, rather than running it in
> > a thread in the compositor?
> > 
> > I would certainly prefer it to be. We would avoid threads in the
> > compositor, and pulling in client side stuff. Now there is a huge risk
> > you might be calling compositor functions from client code, and a crash
> > in the client code would bring the whole compositor down.
> > 
> > If we look at weston-desktop-shell, if it crashes, Weston will respawn
> > it so fast that a user often does not even notice anything happened. 
> > ;-)
> 
> I agree. I apply your comments in v5. it is now process.
> Before, I implemented it as a thread to reduce overhead of process 
> dispatch.
> I experienced such a overhead before. However at first, I shall follow 
> wayland current sample like desktop-shell, invoke it as process.
> If ivi vendor want to it as a thread with the same concerning, it can 
> easily do it by itself.

Hmm, would be interesting to hear a bit more about that overhead
thing.

In your code:
- it is a thread, so it will be subject to scheduling anyway
- it still uses a normal Wayland connections (wl_display_connect),
  so it will not skip any of the communication overheads

I'm just curious about what overheads you intended to avoid here.
Was it library loading at start-up? I can't think of anything else
right now.


Thanks,
pq