Re: [g-a-devel]Re: Why Can't I use BRLTTY With Gnopernicus

["John J. Boyer" <director chpi org>]

Mario,

We're getting somewhere now. Thanks for your explanation. I'l look into 
the brlapi_ignore function. Keyboard emulation on the X virtual console 
was a mighty fine feature, considering it was accidental. Maybe there's a 
more general way to restore it. More on that later.

John
 On Tue, 23 Sep 2003, 
Mario Lang wrote:

> "John J. Boyer" <director chpi org> writes:
> 
> > The thing that is causing me trouble is that keyboard emulation no longer
> > works. It did right after you wrote ttybrl.c . I could
> > pressd the down arrow key combination on my braille keyboard and Gnome 
> > would do a down-arrow. If I was in a text box I could type a character on 
> > the braille keyboard and it would appear on the screen. looking at the 
> > source code for ttybrl.c I can see that it is trying to send keycodes that 
> > have not been mapped somewhere. However, they are not getting a response. 
> > My gues now is that something has changed in Gnome and the keycodes need 
> > to be encoded differently. I have already informed Dave Mielke of this 
> > problem.
> 
> Now I start to understand what you are refering too.  And you are
> actually right, something changed with the way how BRLTTY behaves:
> 
> Keyboard emulation is implemented in BRLTTY directly by opening
> the current virtual console, and inserting a certain keycombination. I
> was actually very supprised to see that it worked in combination with
> X, since the vc opened and inserted into is in that case the X console, and
> not a standard text console.
> At that time, libbrlapi was not forwarding keyboard emulation keypresses to
> gnopernicus, rather brltty was just trying to do its magic, and succeeded.
> Later on, we decided that BRLTTY should forward a lot more keypresses
> to its clients, rather than trying to perform some obscure thing which
> is by no means guaranteed to do the right thing.  Previsouly for instance,
> BRLTTY was not forwaring keypresses like CR_DESCCHAR and friends to its clients,
> which it could not provide any meaningful default behaviour for by itself
> anyway.
> 
> So, what you are seeing is that BRLTTY no longer tries to do keyboard emulation
> on the X console directly, rather it sends a keypress to Gnopernicus.
> However, Gnopernicus has no fascilities for keyboard emulation via
> Braille input yet as far as I can see, so we can not really map those
> keypresses to anything meaningful yet.
> 
> As a short-term solution, you could insert a call to brlapi_ignore into the
> ttybrl.c initialisation function to tell brltty to no longer forward a certain
> keycode-range to Gnopernicus.
> This way, you would get the old behaviour.  Note however, that
> this was IMHO really a feature by accident, it shouldn't be done the
> way it worked.  For instance, since BRLTTY relies on its currently
> defined translation table to figure out which braille key combinations
> are which character, it would behave in a completely broken way whenever
> Gnopernicus has a different translation table loaded than brltty has.
> If you want to see proper Braille keyboard emulation, we will have
> to work on getting this into Gnopernicus first.  I do know that the
> BAUM Vario 80 has the equivalent of a Braille keyboard on it, but I am
> not sure if this is implemented in the Gnopernicus driver yet.
> 
> 
> 
> 
> 
> >
> > John
> >  On Tue, 23 Sep 2003, Mario Lang wrote:
> >
> >> "John J. Boyer" <director chpi org> writes:
> >> 
> >> > So far it looks like brltty is the more likely, because everytime I press a
> >> > key on my braille keyboard, except for a few, there is a message on the tty
> >> > where I invoked startx that says "Default: sending DKxxxx".
> >> 
> >> This message is produced whenever the ttybrl module receives
> >> a keycode which is not yet mapped to a corresponding Gnopernicus braille
> >> keycode. Quoting brltty-3.3.1/Documentation/README.Gnopernicus, the
> >> following table lists BRLTTY keypresses and their corresponding Gnopernicus 
> >> actions.
> >> 
> >>    Command      Binding      Description
> >>    ----------   -----------  -----------
> >>    CMD_LNUP     DK00         Go To Parent
> >>    CMD_HOME     DK01         Go To Focus
> >>    CMD_LNDN     DK02         Go To Child
> >>    CMD_FWINLT   DK03         Go To Previous
> >>                 DK04         Repeat Last
> >>    CMD_FWINRT   DK05         Go To Next
> >>                 DK01DK02     Do Default Action
> >>    CR_ROUTE     HMSnn        Route Cursor
> >> 
> >> Note that "Repeat Last" and "Do Default" are currently not mapped, because
> >> we couldn't think of a really good keycode for them.
> >> 
> >> So, what should work for you is moving left/right and up/down in the
> >> widget hierarchy.  Cursour routing keys, if you have some, should also work.
> >> Everything else is just a question of filling out the case statement
> >> in gnopernicu/braille/libbrl/ttybrl.c in function brltty_brl_glib_cb
> >> to make the corresponding brltty keycodes to Gnopernicus braille keyboard codes.
> >> 
> >> However, note that this does not really prevent you from using Gnopernicus,
> >> since all the navigation functions are mapped on the computer keypad anyway.
> >> 
> >> Note that the reason for the small number of mappings is mainly due to
> >> the small number of default braille key to function bindings in Gnopernicus.
> >> At the time I wrote ttybrl.c, the keycombinations listed above were the only
> >> ones defined in Gnopernicus.  It would not have made much sense to
> >> create more mappings, since they wouldn't have invoked anything anyway.
> >> 
> >> If Braille display support in Gnopernicus increases in flexibility,
> >> it is very easy to add more mappings to ttybrl.c.
> >> 
> >> 
> >
> > -- 
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> > http://www.chpi.org
> > 825 East Johnson; Madison, WI 53703
> >
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> >
> 
> 

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