Re: Automatic paragraph direction and BiDirection layouts in Gtk+

[dov imagic weizmann ac il]

Hi Jonathan,

Regarding Behdad's spec, note that there has been no decision to
implemented it into gtk. I expect it will have to be changed in
several ways until it may be implemented. Look at my comments
regarding what Behdad wrote below. E.g.  the widget alignment 
today is assigned with a floating point number between 0.0 and 
1.0. Adding "inherit" and "against" to such a scheme might require 
an API extension. 

Being familiar with the gtk-sources I feel that I can quite 
safely say that doing the actual implementation is quite easy
once the spec has been written. The tough part was the 
automatic propagation of the base direction that is already
in Gtk-2.4. All that remains is book-keeping of all the settings
and then extracting and overriding the basedirection and the 
alignment from the agreed upon source.

Thus most of the work is reaching an agreement of what should be 
done, and there Owen Taylor has the final word. Thus I believe 
that we should first use the mailing list to reach an agreement,
and then I'll be happy to implement it. 

Regards,
Dov

On Thu, Mar 18, 2004 at 10:39:00AM +0200, Jonathan Ben Avraham wrote:
> Hi Dov,
> Thanks for the URL of Behdad's write-up. Indeed it is a fine piece of
> specification. BTW, I have joined the gtk-i18n-list, so I should see
> Behdad's posts now.
> 
> If I understand the write up correctly, the inheritance of the "direction"
> attribute allows us to override the Bidi algorithm and heuristic for the
> "paragraph_direction" by setting the paragraph_direction to "strong". I
> believe that this solves all of the Bidi problems that I currently forsee
> in the Evolution Hebrew localization.
> 
> The next question is who implements Behdad's spec and when? Do you have
> the time to do it? I am talking to two possible sponsors to get some
> funding for this, BTW.
> Regards,
> 
>  - yba
> 
> 
> 
> On Wed, 17 Mar 2004 dov imagic weizmann ac il wrote:
> 
> > Hi Jonathan,
> >
> > Here it is:
> >
> >   http://mail.gnome.org/archives/gtk-i18n-list/2004-March/msg00001.html
> >
> > I'm very interested to hearing your comments on it.
> >
> > I am also very interested to hear your comments on my response on
> > the subject "RFC on Evolution Localization Requirements". Did you
> > get it?
> >
> > Regards,
> > Dov
> >
> > On Wed, Mar 17, 2004 at 04:47:23PM +0200, Jonathan Ben Avraham wrote:
> > > Hi Dov,
> > > Where can I see a copy of Behdad's write-up?
> > >
> > >  - yba
> > >
> > >
> > >
> > > On Tue, 9 Mar 2004 dov imagic weizmann ac il wrote:
> > >
> > > > Hi Behdad,
> > > >
> > > > Thank you for your very clear write-up. It is as shame that this great
> > > > summary was not available at the design stages of gtk+-2 as I think that
> > > > a few mistakes may have been made that are not reversible.
> > > >
> > > > I'm still not ready to answer the question of how far gtk+ currently is
> > > > from the view that you describe, but here are a few comments from reading
> > > > your message and peaking at the gtk+ source code:
> > > >
> > > > * About "widget direction": gtk+ currently is employing a two layer scheme,
> > > > called direction, and default direction. Both of these may take on the values
> > > > LTR and RTL. The default direction is propagated, wheras the direction is not.
> > > > This is not as good as what you proposed, but it may be good enough.
> > > >
> > > > * Align: gtk+ here uses a floating point value where 0 indicates
> > > > align according to widget direction (which is determined by the contents), 0.5
> > > > means center, and 1.0 means align in direction opposite to the layout direction.
> > > > Here is the translation table between your description and gtk+'s:
> > > >
> > > > 	Behdad                  Gtk-xalign
> > > > 	------                  ----------
> > > > 	align                   0
> > > > 	align-opposite		1.0
> > > > 	center			0.5
> > > > 	inherit			n/a
> > > > 	opposite		n/a
> > > > 	left			n/a
> > > > 	right			n/a
> > > >
> > > > The problem with the current gtk+ API is that since it was the choice
> > > > of using a float instead of an enum, makes it very ugly to extend it and
> > > > add the missing choices! The only way I see is to create floating point
> > > > constants that are outside the 0.0-1.0 range.
> > > >
> > > > * Regarding "paragraph direction" - couldn't this be overloaded with the
> > > > "widget direction". I'm not sure if you intend this to be a paragraph property
> > > > or a widget property. As a widget property it seems that "the default widget
> > > > paragraph direction" and the "widget direction" are close enough to be
> > > > overloaded. As individual paragraphs I wonder why you chose "strong"
> > > > instead of "rtl" and "ltr"? In any case gtk+ currently does not define this,
> > > > and with the latest BiDi patch, the paragraph direction is always according
> > > > to the resolved direction of the contents.
> > > >
> > > > I have a few ideas of what may be done, but I'd prefer to send this away
> > > > as soon as possible.
> > > >
> > > > Thanks again for your great summary.
> > > >
> > > > Regards,
> > > > Dov
> > > >
> > > > ----
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> > >
> > > --
> > >  EE 77 7F 30 4A 64 2E C5  83 5F E7 49 A6 82 29 BA    ~. .~   Tk Open Systems
> > > =}------------------------------------------------ooO--U--Ooo------------{=
> > >      - yba tkos co il - tel: +972.2.679.5364, http://www.tkos.co.il -
> > >
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> -- 
>  EE 77 7F 30 4A 64 2E C5  83 5F E7 49 A6 82 29 BA    ~. .~   Tk Open Systems
> =}------------------------------------------------ooO--U--Ooo------------{=
>      - yba tkos co il - tel: +972.2.679.5364, http://www.tkos.co.il -
> 
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