Re: Questions about gnome-mag + orca

[David Bolter <dtb gnome org>]

Kristian Lyngstøl wrote:
> On Thu, Mar 27, 2008 at 8:36 PM, Willie Walker <William Walker sun com> wrote:
>   
> >  Having said all that, we have a task for "GNOME Outreach Program:
> >  Accessibility" for someone to get paid to help take the magnification
> >  solution beyond where we are now.  If someone is interested in this,
> >  please let us know!
> >     
>
> I'm unsure of what the plans forward for gnome-mag is. It has been my
> understanding that it is mostly in maintenance mode?
>
> Before I go further into this, I'd like to sum up my understanding of
> the magnification-related technologies involved (only listing
> magnification-related tasks).
>
> Orca:
>  - Collects data on what's going on. Mouse movement. Window focus.
> Cursor movement, etc.
>  - Controls Gnome-mag (soon to be over DBus?)
>
> Gnome-mag:
> - Just does magnification.
> - Can be composite manager, but doesn't require it.
> - Uses XRender
> - Conflicts with other composite managers (like Compiz).
> - Has performance issues in may situations.
>
> Compiz:
>  - Must be a composite manager.
>  - Provides various plugins for accessibility, including "magnifier" and "ezoom"
>  - Currently requires OpenGL, plans exist for other rendering engines
> (including XRender). *
>  - NOT the default Gnome window manager
>  - Flexible; adapting plugins or even the core for a11y is easily accomplished.
>  - The hardware (driver) requirements seem to be the major blocker for
> this to really take off.
>
> Metacity:
>  - Default Gnome window manager and also composite manager
>
>
> With regards to Compiz, there is working going on which will make
> Compiz less hardware dependant and generally better all around,
> including for a11y. This is a long term effort though.
>
> That leaves us with a gnome-mag which, in it's current state, would be
> by and large useless due to performance issues. I've read Carlo's idea
> about having the composite manager draw into an off screen window
> belonging to an other application, but I'm not sure I'm buying it.
> Might as well just tell the composite manager to magnify to the right
> place to begin with.
>
> However, making textures/window content available between applications
> is also something that I know there is a lot of interest in. And some
> work exist (Compatible video players can give Compiz direct access to
> their textures through the Video plugin).
>
> Depending on Compiz entirely is going to be hard to sell. I am also
> unfamiliar with Metacity code. I still believe that the integration
> between Orca and eZoom should be finished similar to how it was
> discussed during the Accessibility Summit, but that still leaves
> Gnome-mag and metacity.
>
> I'm honestly not sure what should be done about gnome-mag. Obviously
> the compositor in Metacity also complicates things, as metacity does
> not currently offer any magnification, thus it basically just kills
> performance for gnome-mag without giving much back.
>
> Having gnome-mag interact with Compiz isn't really had, but then I
> believe we might as well just skip Gnome-mag all together. It's
> straight forward to make or adjust a Compiz plugin or two to act
> exactly like Gnome-mag.
>
> This introduces some code duplication though, which I see as the major
> selling point for gnome-mag staying alive. So let's look at what
> exactly Gnome-mag does, help me fill in the blanks as I have very
> limited gnome-mag experience.
>
> - Allow external control (from orca?)
> - One area zoomed, an other not zoomed.
> - Mark the position of the mouse
>
> Having gnome-mag control these functions but the compositor actually
> performing them seems feasable to me. This would allow gnome-mag to
> retain a lot of it's logic, but the compositor to do the actual work.
> This way, gnome-mag could also fall back to it's own xrender method
> without a significant code duplication, and the experience should be
> consistent across different composited window managers. I'm still not
> quite convinced this is the way to go though.... It seems too much
> like we're just striving to keep gnome-mag alive. It would, with a
> composite manager, basically just filter and relay messages from Orca
> or other controlling programs.
>
> If significant work is to be done on gnome-mag, I believe we need to
> rethink it's place. And what to do with Metacity. There obviously
> needs to be SOME sort of interaction between a composite manager and
> whatever is responsible for triggering or controlling magnification.
> I'm not sure how much magnification-code would be acceptable in
> metacity either, or if it's even suited for it at all.
>
> So I guess I'm not any closer to answering my own question: What
> exactly should be done with magnification?
>   

My 2 cents:

I say move forward with composite magnification. Create dbus api for 
compiz if that makes the most sense. Let's move forward.

cheers,
D