[g-a-devel]Re: Gnome 2.0 : accessibility for the gnome-cd application

[Marc Mulcahy <marc mulcahy sun com>]

Hi All,

We could implement an AtkObject on behalf of CdDisplay, maybe call it 
AccessibleCdDisplay for discussion.  This AtkObject would inherit its 
AtkComponent interface from GailWidget (note that the headers for 
GailWidget are not exported, but through the mechanism illustrated in 
libzvt and gtkhtml2 head, widgets can inherit from 
it).  AccessibleCdDisplay would expose an accessible name of "CD Display" 
and an accessible description of "Displays information about the currently 
playing album and track"... or something like that.

AccessibleCdDisplay would also provide an implementation of get_n_children, 
which would always return 4 (a child for each pango layout).  And then of 
course it would also have to implement ref_accessible_child to allow access 
to those children.

Then, we could implement an AtkObject to provide accessibility on behalf of 
the PangoLayouts, let's call it 
AccessibleCdDisplayChild.  AccessibleCdDisplayChild would implement AtkText 
on behalf of its contained PangoLayout.  Note that most of the functions 
necessary to do this are exported and are defined in gailmisc.h, so this is 
a relatively painless process.

The only sticky point with implementing accessibility on behalf of a 
PangoLayout is GetCharacterExtents, which requires screen cordinate 
information about the locations of individual characters, and the Gail 
implementations for this function on behalf of GtkTextView currently rely 
on GtkTextBuffer private API.  Is there a way to determine the exact 
location of individual characters in a PangoLayout?  Maybe a peak at 
GailLabel will shed some light...

Just my thoughts...

Marc




At 03:53 PM 2/4/2002 +0530, JAYARAJ P R wrote:
> Hi,
>
> The gnome-cd application has a custom widget called CDDisplay which forms
> the display area where the information about the time elapsed, album name,
> artist name etc appears. The parent of this CDDisplay custom widget is a
> GtkDrawingArea. It contains 4 lines of PangoLayout each of which display
> information about the time elapsed for the current track, album name and
> artist name.
>
> As part of accessibility, i feel that this custom widget requires AtkText
> interface to be implemented. The atk_text_get_text() interface of AtkText
> would return the time elapsed, album name and artist name when the focus is
> on the CDDisplay custom widget. Most of the other interfaces in AtkText
> doesn't seem
> to make enough sense in this case and would be no-op functions.
>
> Anyone got different ideas?
>
> Regards,
> Jayaraj
>
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