[PATCH weston] compositor: Separate hardcoded backend related code from compositor

[JoonCheol Park]

Hi Giulio, pq!


2015-06-23 20:57 GMT+09:00 Pekka Paalanen <ppaalanen at gmail.com>:

> On Tue, 23 Jun 2015 14:14:53 +0300
> Giulio Camuffo <giuliocamuffo at gmail.com> wrote:
>
> > Hi,
> >
> > This kinda goes in the opposite direction to my libweston patches. In
> > that series i move the command line handling away from the backends
> > code to make them work in multiple compositors. This moves even more
> > compositor-specific stuff in the backends so we need to decide if we
> > want this or libweston.
>
> We want libweston.
>

I just quick review the libweston on the github (
https://github.com/giucam/weston/). When it will be applied to mainstream ?

My understanding about libweston is for reuse the x11/drm related code for
other compositor project (like libinput). Yes, It is everyone want :-)
But, since the backend structure which manages multiple plugins and load
symbol 'backend_xxx()'  is weston compositor specific stuff and it is not
in the scope of libweston, I believe my proposal is not the opposite idea
to the libweston what you are preparing.
(In your repository, my proposal may change the src/weston.c to remove
hardcoded backend option outputs. It is not part of libweston library. )



> > 2015-06-23 13:29 GMT+03:00 JoonCheol Park <jooncheol at gmail.com>:
> > > Instead of adding available backends and usage outputs at build time,
> > > this patch finds all available backend plugins in MODULEDIR and prints
> > > them. It also prints usage output for selected backend by calling
> > > "backend_usage()" in the plugin.
> > >
> > > By this patch, we can remove all hardcode for backends from compositor.
> > > 3rd party backend plugin can be listed in help output. Backend
> developer
> > > can freely add additional description for backend.
> > >
> > > Signed-off-by: JoonCheol Park <jooncheol at gmail.com>
> > > ---
> > >  src/compositor-drm.c      |  11 ++++
> > >  src/compositor-fbdev.c    |   9 +++
> > >  src/compositor-headless.c |  11 ++++
> > >  src/compositor-rdp.c      |  15 +++++
> > >  src/compositor-rpi.c      |  12 ++++
> > >  src/compositor-wayland.c  |  14 +++++
> > >  src/compositor-x11.c      |  13 +++++
> > >  src/compositor.c          | 141
> ++++++++++++----------------------------------
> > >  src/compositor.h          |   3 +
> > >  9 files changed, 125 insertions(+), 104 deletions(-)
>
> JoonCheol, any particular reason you are proposing this?
> Are you building external backends?
>

Yeap, I'm trying to make some fun experiments based on headless backend
code.
When I tried to add new options for backend plugin, I had to add option
outputs for my backend into main compositor code. not in the plugin itself.
Since it is kind of hardcode, I thought it doesn't look good. I think that
plugin should have such information of itself and compositor should load
such information from plugin file.

(similar case: In case of NPAPI, Web browser can show plugin's information
by getting/calling "NP_GetMIMEDescription()" from each plugin .so file. e.g
- about:config in Mozilla)

So, I created this patch for better (weston specific) backend plugin
management structure.


> AFAIK the Weston SDK (the installed headers) for external plugins never
> supported external backends, so I'm curious.
>
>
Since this kind of plugin just need header files for building and weston.pc
is also already supported, I thought that building external backend plugin
is supported (and ideally possible in current version of weston)... but
wasn't it??
If it can be supported, it would be good for like my case. Developer can
create the backend plugin without build all weston source.. (like other
'-dev' pkg supported program)


We are going in the direction of backends becoming libweston internal
> details, not something you can plug and switch arbitrarily, at least
> for the middle-term.


>

> Thanks,
> pq
>
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