[HarfBuzz] Using Harfbuzz & ICU & Glyphy in OpenES2 Engine

[Vincent Isambart]

Hi Jeremy,
> Font fallbacks I don't bother with. Script-itemization and BIDI I'm not
> even sure what they are. :)

Script-itemization is splitting your text in runs of characters of the same script (script being for example latin characters, Chinese characters, Arabic, Hebrew, Hiragana, Katakana, Hangul…)
BIDI is handling text mixing left-to-right (like all languages using latin characters) and right-to-left (like Arabic or Hebrew), for example if you want to put an English name in a phrase in Arabic.
> Does anyone else have any comments on my original post? I mean, EVERYONE
> using harfbuzz is doing what I'm doing, how are they doing it? :)

From what I understand, currently the main users of Harfbuzz are pretty big codebases: browsers (Chromium, Firefox) and toolkits (Qt, and Pango – Pango being used of course for Gtk+), all of them reimplementing most of this.  

It seems Behdad is planing on working on at least some of this for his "next library” but he seems to be a busy guy so who knows when it will be released ;-).

Thanks,
Vincent




On Tuesday, February 11, 2014 at 8:02, Jeremy Moles wrote:

> Hey, thanks for the response; chronotext is a cool site. :)
>  
> On 02/09/2014 04:01 AM, Ariel Malka wrote:
> > Hi Jeremy,
> >  
> > I have developed a solution based on Harfbuzz and ICU for rendering  
> > Unicode text with C++ and OpenGL from the ground-up:
> > https://github.com/arielm/Unicode
> >  
> > The topic of line-breaking is also on my agenda (more on the long  
> > term, nothing urgent...)
> > One of the directions I'm planning to check in the future:  
> > https://github.com/adah1972/libunibreak
> >  
> > I wonder how do you handle topics like font-fallback,  
> > script-itemization and BIDI, prior to shaping and line-breaking?
>  
>  
>  
> Font fallbacks I don't bother with. Script-itemization and BIDI I'm not  
> even sure what they are. :)
>  
> Does anyone else have any comments on my original post? I mean, EVERYONE  
> using harfbuzz is doing what I'm doing, how are they doing it? :)
>  
> > Regarding one of your questions, it's easy to pass to Harfbuzz some  
> > text previously processed with ICU, as demonstrated here:
> > https://github.com/arielm/Unicode/blob/v4.0.0/Projects/Rendering/src/TextRun.h#L50
> >  
> > HTH,
> > Ariel
> > http://chronotext.org
> >  
> >  
> > On Sat, Feb 8, 2014 at 12:01 AM, Jeremy Moles <cubicool at gmail.com (mailto:cubicool at gmail.com)  
> > <mailto:cubicool at gmail.com>> wrote:
> >  
> > Hey guys! I'm working on a Python3-based OpenGL library and I want
> > to use the union of Harfbuzz and libicu to do some (a small
> > subset) of what Pango currently does. I cannot, unfortunately,
> > simply use Pango, as its dependency chain will likely stop my
> > clients' interest dead in its tracks. Further, there are some
> > issues when customizing Pango's rendering model (and I'm not
> > speaking without experience here, I've done it when I wrote
> > osgPango) that aren't ideal to work with.
> >  
> > So, I would like to use hb and icu to accomplish some very basic
> > layout in my OpenGL scenes (note: I will also be using Glyphy
> > instead of my own rasterized SDF font textures too). I will need
> > basic left|right|center alignment (potentitally justify, but it
> > isn't a request yet), some basic markup support, etc.
> >  
> > I nearly have everything working locally, but the one area I'm
> > having a lot of trouble with is knowing how--and in fact, WHOSE
> > responsibility it is--to determine how to break large lines of
> > text given my sizing constraints. This doesn't appear to be
> > something harfbuzz attempts to do, but it may have helper
> > functions nonetheless.
> >  
> > What I'm looking for are a few hints on how people (Behdad?) might
> > tackle this problem. ALL text in this library gets converted in
> > whitespace-normalized UTF8 using libicu and line breaks can only
> > be FORCED by using <p/> or <br/> markup. Otherwise, all breaks
> > should behave similarly to how they do in HTML.
> >  
> > If I feed my force-delimited lines of text (that is, break my
> > input feed up by <br>/<p>) one huge chunk at a time to harfbuzz, I
> > can get the extents for each glyph as if I had unlimited X
> > coordinate space. I can use these extents to position as required
> > by the calling function, but again, I'm having trouble determining
> > where it is safe to break.
> >  
> > Is this something libicu can handle? Can harfbuzz make it easier?
> >  
> > NOTE: When I "whitespace normalize" my string before ever passing
> > it harfbuzz, I use the UBRK API of libicu. There are also
> > functions like:
> >  
> > u_isspace()
> >  
> > ...which look promising, but it expects a UChar32, which I do not
> > know how to easily fetch while using harfbuzz's UTF8 functions,
> > who operate on potential multibyte chars.
> >  
> > Thanks in advance!
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