The case for a "SceneGraph"

[Michał Sawicz]

W dniu 25.07.2013 01:28, Robert Carr pisze:
> I don't mean to raise FUD but it is unclear enough to me that I would
> not know the first step if assigned it as a task (My first question
> would be, does ms::Surface implement QQuickItem? If not, how do we avoid
> two copies of the SurfaceStack). I also think that, ease of applying
> graphical effects, is not really something holding us up at the moment,
> or something likely to be a significant drain on development resources
> any time soon.

The biggest benefit that I would see from this is the ability to
composite a surface on top of another, treating it as any other Item in QML.

My usecase: being able to render $your_favourite_part_of_the_shell_ui
out-of-process, while maintaining all of the transitions & animations
designed for that part of the UI.

Reason: stability, security, flexibility. This would mean, that, for
example, the video player could be embedded in the dash video preview
without the risk that it would bring down the shell if the video file
was broken.

There's only so much that we can do to a surface between shell and mir
to not grow the amount of communication. Obviously geometry, opacity,
scale are the most important things, but they're also the easiest. More
complex things like rotation, darkening, desaturation, not to mention
blur, will have to be implemented outside of QML and just "driven" by
some custom properties of the surface item in the QML tree. But we're
limited to whatever mir and/or unity-mir implement.

Don't get me wrong, I'll understand if you say "this can't be done"/"is
not feasible". I just want you to think about why is that, and if maybe
we can think of making it possible / feasible.

g'night,
-- 
Michał (Saviq) Sawicz <michal.sawicz at canonical.com>
Canonical Services Ltd.

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