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

[Ariel Malka]

Hi Vincent,

> Out of curiosity, I think you're already using ICU,
> so why would you use libunibreak and not ICU's line break iterator?

The truth is that I have not yet started to tackle the issue of
line-breaking, so everything is open / vague / frightening at this stage...

A+


On Tue, Feb 11, 2014 at 2:00 PM, Vincent Isambart <
vincent.isambart at gmail.com> wrote:

> Hi Ariel,
>
> Out of curiosity, I think you're already using ICU, so why would you use
> libunibreak and not ICU's line break iterator?
>
> Thanks,
> Vincent
>
>
> On Sunday, February 9, 2014 at 18:01, 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?
> >
> > 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)> 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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