Since it has a couple of left-"matras".

Through the Arabic shaper.  It's similar to Mongolian.

The merger of normalizer and glyph-mapping broke shapers that
modified text stream.  Unbreak them by adding a new preprocess_text
shaping stage that happens before normalizing/cmap and disallow
setup_mask modification of actual text.

To room for more allocations, coming.

Hookup some Indic data to it.  More to come.

If there is no GPOS, zero mark advances.

If there *is* GPOS and the shaper requests so, zero mark advances for
attached marks.

Fixes regression with Tibetan, where the font has GPOS, and marks a
glyph as mark where it shouldn't get zero advance.

Enabled for all shapers except for Indic.

Add a shaper class struct.

When we removed the separate Hangul shaper, the specific normalization
preference of Hangul was lost.  Fix that.  Also, the Thai shaper was
copied from Hangul, so had the fully-composed normalization behavior,
which was unnecessary.  So, fix that too.

Fixes all Tibetan failures.  All 180k of them!

Merges back Hangul into the default shaper.

In a new callback...  Currently unused by all complex shapers.

This is to incorporate it into GSUB/GPOS processing.

Like Uniscribe does.

That's not in the OpenType spec, but it's what MS and Adobe do.

Previously, we were NOT actually recomposing Hangul Jamo.  We do now.
The two lines in:

test/shaping/texts/in-tree/shaper-default/script-hangul/misc/misc.txt

Now render the same with the UnDotum.ttf font.  Previously the second
linle was rendering boxes.

We can also start applying OpenType Jamo features later.  At this time,
I have no idea how the 'ljmo', 'vjmo', 'tjmo' features are supposed to
work.  Maybe someone can explain them to me?

In preparation for Hangul shaper.

This is the most convenient way to browse scripts.

As requested by Jonathan Kew.

We need to devise a better mechanism to choose which scripts to
pass through the Indic shaper.  Moreover, currently we are storing
data for some scripts in the Indic shaper that are not even going
through that shaper.  Need to find a better way...

Based on patch from Jonathan Kew.

Where causing issues for people with MSVC.

This allows the Indic shaper to request decomposed characters.  This will
handle split matra for free.  Other shapers prefer precomposed
characters.

Nothing functional in there yet.

So far, we're parsing IndicSyllabicCategory.txt and IndicMatraCategory.txt
fils from Unicode Character Database and store them in an array to be used
by the shaper.  Also hooked up the shaper, but it does not do anything
right now.