[HarfBuzz] Using Harfbuzz & ICU & Glyphy in OpenES2 Engine
cubicool at gmail.com
Fri Feb 7 23:01:49 CET 2014
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:
...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!
More information about the HarfBuzz