[HarfBuzz] Harfbuzz version

[Chris Scaife]

Thanks for reading my posts :)

Currently all terminals have control sequences that are based on left to
right. I want to create an enhanced low level with bidirectional controls:
plot glyph and move left, plot glyph and move right, return to left margin -
return to right margin, erase to end of line left and erase to end of line
right etc.

The Unicode algorithm is probably fine from the user's perspective, but at
the display level in a terminal or terminal emulator one needs to know at
least which margin a line is anchored on and be able to index a character by
position on that line: It is not practical to scan what is recorded for each
line while reversing the Unicode algorithm as we go.

Thus I felt I cannot work with a widget like GtkTextView and other display
widgets that have integral Unicode bidi to render their display.

On 18 November 2010 07:49, Behdad Esfahbod <behdad at behdad.org> wrote:

> On 11/12/10 16:36, Chris Scaife wrote:
> > Thanks for that reply :)
> > I did indeed look at using Cairo/Pango but I was really struggling with
> > them. A lot of this was due to the integral Unicode bidi algorithm that
> > makes it nearly impossible for me to know where any particular character
> > is being placed.
>
> Not as much as you make it sound.
>
>
> > Thus at the low level I want to do a much simpler bidi algorithm with an
> > expicit LRE/RLE for every direction change. Indeed I recently did drop
> > down to Xft but now having a hard time using it with Gtk and still
> > unable to understand how the font is selected e.g. you can see images of
> > the problem plotting Chinese and Arabic
>
> I  strongly recommend against making up your own bidi algorithm...
>
>
> behdad
>
>
> > I suppose the main thing is that it's all good learning experience and
> > perhaps when I actually know enough I'll be able to make a genuine
> > contribution on the vte widget :) When I got the source code for it a
> > while back I got hopelessly lost :(
> >
> > On 13 November 2010 10:11, Behdad Esfahbod <behdad at behdad.org
> > <mailto:behdad at behdad.org>> wrote:
> >
> >     On 11/12/10 15:48, Chris Scaife wrote:
> >     > Hello all,
> >
> >     Hi Chris, welcome to the list.
> >
> >     > I am writing a terminal emulator as an learning experience and
> would
> >     > like to do a comprehensive implementation.
> >
> >     Humm.  Being the maintainer of 'vte' myself, may I suggest that you
> >     consider
> >     studying the vte code and contribute there?  We can use a couple
> hands.
> >
> >     > For compatibility with things
> >     > like ncurses I need to have full control of glyph positioning and
> so I
> >     > feel my best option might be to interface the font stack through
> >     Harfbuzz.
> >     >
> >     > Where can I find a Harfbuzz distribution and description of the
> >     current
> >     > API that I can use with my project please?
> >
> >     Unless you want to support Indic, Arabic, etc, it would be easier to
> >     just use
> >     something like cairo or Xft directly.  If you still rather use
> >     HarfBuzz, well,
> >     this is the one paragraph summary:
> >
> >
> http://lists.freedesktop.org/archives/harfbuzz/2010-October/000905.html
> >
> >
> >     Cheers,
> >     behdad
> >
> >     > Thanks in advance
> >     > Chris
> >
> >
>
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