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

[Nobuhiko Tanibata]

2014-07-07 17:04 に Pekka Paalanen さんは書きました:
> 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 for comment, pq!

My concerning was that process dispatch vs thread dispatch. Threads 
share their memory space and the dispatch cost might be smaller than 
process ones. If I can implement IVI clinet in the same process, it can 
reduce dispatch code compare to process dispatching.

BR,
ntanibata

> 
> Thanks,
> pq