[HarfBuzz] Eager CS undergrad thirsty for knowledge about the inner bowels of typeface rendering. Specifically for supporting vertical ligature caret definitions.

[Luis de Bethencourt]

Hello Robin,

I am in the opposite place you are. I come from the Computer Science world
and want to learn more about Typography and how computers handle it. We
should help each other!

Where did you learn all the typography/font concepts and terms you know?
Recommend any good resource to learn this?
Which is this IRC channel you mentioned?

If you want to play with Harfbuzz, I recommend this example code:
https://github.com/lxnt/ex-sdl-freetype-harfbuzz

Your idea of having a dissection of font files similar to the famous
dissection of executable files is a really good one.
What do you people in the list thing is a good format to start such a
project?

Cheers,
Luis


On 29 January 2014 18:21, Robin Skahjem-Eriksen <
robinds at student.matnat.uio.no> wrote:

> Thanks for link. I shall make sure to read up on that.
> I am have slowly started the process of writing some software for Tibetan
> writing. I thought about how to handle the complex caret behaviour, when
> people on IRC stated that I should look into getting that done deeper in
> the text rendering stack.
>
> Do you know if Graphite currently support caret placements for ligatures
> which have been transmuted from a stack of glyphs?
>
> -Robin
>
>
> On Wed, Jan 29, 2014 at 02:37:18PM -0500, Ed Trager wrote:
> > Hi, Robin,
> >
> > You might also want to read up about Graphite:
> >
> >
> http://scripts.sil.org/cms/scripts/page.php?site_id=projects&item_id=graphite_home
> >
> > I believe that Graphite has more sophisticated support (compared to
> > OpenType technology) for caret placement for complex scripts such as
> > Tibetan.  On the flip side, in comparision to OpenType, Graphite is not
> > widely used.
> >
> > - Ed
> >
> >
> > On Mon, Jan 27, 2014 at 7:32 PM, Robin Skahjem-Eriksen <
> > robinds at student.matnat.uio.no> wrote:
> >
> > > I have started to investigate into the matter and I find that there is
> > > very sparse information readily available. Microsoft had a very
> interesting
> > > document, which I have been trying to understand:
> > > http://www.microsoft.com/typography/OpenTypeDev/tibetan/intro.htm
> > > In the section "Examples of Tibetan" (bottom of document), the first
> > > example shows how a sequence of eight code points are strung together
> to
> > > form a Tibetan "syllable". It's not really a syllable. It's called a
> > > tsheg-bar in Tibetan and a Tibetan word can consist of multiple of
> these.
> > > Anyways, all the code points from the second one up to and including
> the
> > > fourth one are as far as I can tell formed into a ligature. I have
> opened
> > > the MS Himalaya font in Fontforge and seen that this ligature is
> defined as
> > > "tibSa_Ga_Rata_Shapkyu" in a location outside of the Unicode address
> space.
> > >
> > > Now, if a user is to work with Tibetan text like any other user of a
> roman
> > > script language, the user of Tibetan script would be very
> disappointed. The
> > > reason for this is that it is impossible to place the caret and select
> > > individual characters in this ligature. As of now, you can only select
> the
> > > entire stack as a whole selection. This is partly because the glyphs
> have
> > > been transmuted into a ligature, but perhaps also because there seems
> to be
> > > no definitions of vertical caret ligatures anywhere.
> > >
> > > How would one go about defining such an important feature? Should this
> be
> > > implemented in the font? Should it be implemented in the software that
> > > handles the type face? Or perhaps both? While digging through the MS
> > > Himalaya font, I found that there is a value for a Ligature Caret
> Count.
> > > What is this value supposed to be used for? For the ligatures that are
> > > supposed to represent stacks of multiple glyphs, the Ligature Caret
> Count
> > > had values up to 4, which I hope can mean that the font itself
> contains the
> > > information I am looking for. Is my assumption correct?
> > >
> > > Also. I am highly willing to learn more about the inner bowels of
> typeface
> > > rendering. I have taken a course on Computer design and understand how
> > > everything are bits and how Asssembly language and C handles this. I
> also
> > > understand the general idea about Unicode and how this is defined on a
> low
> > > level. I've also understood that fonts are basically Bézier curves
> which
> > > are rasterized to the screen buffer. There is still a lot of this
> process
> > > which I still find very murky, so if anybody knows any in depth reading
> > > material, I would be very happy to start reading those. I have read
> State
> > > of Text Rendering by Behdad Esfahbod, which was a great overview of the
> > > text rendering stack. But I would really like to get more in depth
> > > understanding of each layer in the stack.
> > >
> > > I would really like to also learn more about Harfbuzz and how to work
> on
> > > it. I would really love to spend some time working on it, if I am at a
> > > level where my code submission would be acceptable to the standards of
> this
> > > project. Is there any documentation for Harfbuzz? I've taken a quick
> glance
> > > at the source code and run some scripts and make commands, but I
> honestly
> > > don't know what's going on. Why are the C files named .cc and some of
> the
> > > header files named .hh? I can recognize some font lingo and have a
> slight
> > > understanding of what might be going on, but it would be really
> helpful to
> > > have something like this for an Openfont file:
> http://imgur.com/a/JEObT#0.
> > > I must also say that I have no idea of what harfbuzz is supposed to do
> and
> > > how I test or use it once it's compiled. I've tried running some shell
> > > scripts and bin files that were compiled, but I really have no clue.
> > >
> > > Is there somewhere I can learn how to get a handle on understanding the
> > > technicalities of the Harfbuzz project and learn what I need to start
> > > contributing?
> > >
> > > Sincerely,
> > > Robin Skahjem-Eriksen
> > > _______________________________________________
> > > HarfBuzz mailing list
> > > HarfBuzz at lists.freedesktop.org
> > > http://lists.freedesktop.org/mailman/listinfo/harfbuzz
> > >
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