Re: Unify the Platforms: Cairo+FreeType+Harfbuzz Everywhere (except TTY)

[Pip Cet <pipcet@gmail.com>]

On Sun, May 17, 2020 at 3:56 PM Eli Zaretskii <eliz@gnu.org> wrote:
> > Date: Sun, 17 May 2020 16:59:53 +0200
> > From: Julius Pfrommer <julius.pfrommer@web.de>
> > Cc: emacs-devel@gnu.org
> Next, please be aware that we already made the decision to use
> HarfBuzz as our main text-shaping engine.

That's a decision that, having just played with HarfBuzz, I find
puzzling. It appears to have no practical support for treating
ligatures as anything but monolithic glyphs: is there a documented way
of getting HarfBuzz to tell you which part of the "ffi" ligature is
the middle "f"? I suspect the answer is "there are some languages
whose scripts don't allow for the equivalent operation, so we won't
support it at all, as a matter of principle".

I'm not sure PangoCairo does better, but whatever Libreoffice uses
appears to get the job done, so at least one display engine out there
solves this problem.

(This is assuming we want kerning, ligatures, and subpixel rendering
for English text. "Real" text shaping, composition, reordrant glyphs,
and bidi concerns are something that I can't really comment on, beyond
admitting that, of course, supporting the world's major languages at
all is more important than supporting English with the typographic
finesse we currently lack).

Years ago, I ran a WebAssembly version of Emacs in a web browser.
(Back then, I used a terminal emulator written in JavaScript.) I'd
certainly like to do that again some day, and I think a hard
dependency on Cairo and FreeType would make that even harder.