[maemo-developers] Fremantle OpenGL wrapper?

[From: Qole]

On Tue, Jun 2, 2009 at 3:04 PM, David Greaves <david at dgreaves.com> wrote:

>
> I understood that GL wasn't going to be available to the apps on the
> device...
> something about the window manager permanently taking the only viewport?
>
> I am not sure if this is a beta-phase bug or a hardware or GLES issue.
>
> David
> --
> "Don't worry, you'll be fine; I saw it work in a cartoon once..."
>


I think you are referring to the following two posts, both by Kimmo
Hämäläinen. I don't believe they say that GL won't be available, but that
there will be a performance hit because the apps will have to go through
Hildon-Desktop to render, rather than rendering directly.

http://lists.maemo.org/pipermail/maemo-developers/2009-March/018639.html

As Kate has already proven, multi-context works.
> But as long as you have hildon-desktop running in the background, you
> will not render directly to the screen even if you use
> Clutter/QtGraphicsView/EGL+OpenGLES2.0/whatnot in your application. When
> hildon-desktop is running, it is the only one drawing on the screen
> (with the exception of XVideo). So, killing hildon-desktop is the only
> way to get direct rendering to the screen at the moment. (We might have
> something more elegant for this in the future...)
>

http://lists.maemo.org/pipermail/maemo-developers/2009-March/018645.html

Keeping the compositor around has some performance impact, because after
> the application draws to an offscreen pixmap (the window), the X server
> sends Damage events (saying "this part of the pixmap changed") to
> hildon-desktop, and hildon-desktop asks the 3D HW to use this pixmap in
> a OpenGL texture and draw it to the screen. So, there is some extra
> delay (maybe 10-25ms) after the application's drawing is visible.
>
> Second implication is that you cannot use HW accelerated zooming and
> moving of textures for the whole graphical pipeline. You can use it for
> drawing into your window, but when hildon-desktop draws to the screen,
> it cannot use it (e.g. it cannot say "move this content to there"). It
> will just get a big damage area that is updated by updating the OpenGL
> texture content.
>
> Third implication: to save memory, we are using the texture-from-pixmap
> GL extension to allow the X server and 3D HW share the pixmap data. This
> means that while 3D HW is accessing the pixmap data (while transferring
> it to the 3D chip), X server cannot access it. Thus, while the
> compositor is updating the screen, it is slowing down X drawing.
> However, it's not mandatory to use texture-from-pixmap, but then you are
> paying the price in increased RAM usage.
>
>


-- 
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engages it; one who is influenced by a peculiar fervor of mind; an ardent
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