Re: Linux Window Managers and Accessibility

[Bill Haneman <Bill Haneman Sun COM>]

Carl said:

>Bill Haneman <Bill Haneman Sun COM> writes:
>
>> Sasha said:
>> 
>> >Host name might be a better solution, and by the way, fits into 
>> existing
>> >standards - ICCCM WM_CLIENT_MACHINE property could be used.
>> 
>> 
>> Right, thus the suggestion of char* for the parameter type in the method 
>> mapping application ids (including hostname) to Desktops.
>
>Hostname is also not guaranteed to be unique.

It should be unique within the context of the accessibility client-server 
relationship, or else completely transparent (e.g. app must migrate seamlessly 
if physical host is transient).

>> Carl said:
>> >>
>> >> I'm not sure I understand the problem exactly.  Does the
>> >> AccessibilityBroker connect to the X server?  If so, I would think
>> >> that the Window ID of some distinguished window in the application
>> >> would be a better identifier.
>> 
>> Not all accessible applications will have associated windows.  Also it's 
>> not clear which window should be "distinguished".  The 
>> AccessibilityBroker itself has no inherent reason to connect to X.

Actually my previous assertion (broker does not need X) is not entirely true 
since the broker supports event synthesis.  But, as I note below, the 
requirement is to avoid X "dependencies", not avoid using X altogether - in 
other words the SPI should not have things in it that are X-centric or 
difficult to implement outside of X.

>I don't understand the architecture here, I guess...although that
>might not matter.
>
>What accessible applications would not have windows?  Sound-only?
>Console-only?  Anyway, any application which connects to the X server
>at all can create a never-mapped window and use its ID as the
>AccessibilityBroker identifier.  (Applications which don't connect to
>the X server don't matter in this context, right?)

I am not sure this is entirely true.  In an accessibility context applications 
might not have any non-accessibility I/O at all (i.e. no windows, no sound, no 
console).  At any rate the architecture should not have any (explicit) X 
dependencies, as it needs to be portable across architectures (gtk has been 
ported to Win32, for instance).  

>> The goal here is to map an accessible application's unique 
>> identification info (provided by the app when it registers with the 
>> AccessibilityBroker) onto the appropriate desktop/desktops.
>
>Why not have the AccessibilityBroker give a unique identification
>token to the application when it registers?  The application can pass
>that on to the window manager.

I agree with the first part, but what (existing) API for the window manager 
would one use to pass this info to the window manager?  The key issue is that 
the window manager must be able to map application identifiers to virtual 
desktops.  As you point out if the application is not using the window manager 
(in other words, maps no windows) then the window manager can report that, and 
the broker can choose to map it to desktops according to its own heuristics.

-Bill

>Carl Witty
>
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------
Bill Haneman x19279
Gnome Accessibility / Batik SVG Toolkit
Sun Microsystems Ireland