Shape Khmer and Myanmar as HarfBuzz does

Two more shapers on the syllabic groundwork, from HarfBuzz 10.2's
source. Khmer reorders before any lookup: a coeng and Ro go before the
base, masked for pref, what follows them for cfar, a left matra goes
first; split matras decompose with U+17C1. Myanmar finds the base after
a kinzi, gives each glyph its place around it and sorts by place, and
zeroes mark advances before GPOS rather than after.

Noto Sans Khmer and Noto Sans Myanmar shape as HarfBuzz does at 20,000
runs a plan, and so do Unifont's Khmer and Myanmar (no GSUB).

1 files changed, 6 insertions, 3 deletions

diff --git a/text/shape.h b/text/shape.h
index 7b12009..7f02729 100644
--- a/text/shape.h
+++ b/text/shape.h
@@ -6,8 +6,8 @@
 
 /* Shaping (docs/design/004-text.md): a run of characters (one script, one
  * direction) to glyphs and their positions, as HarfBuzz 10 shapes it with
- * its default, Arabic, Hebrew, Hangul and Indic shapers, glyph for glyph and
- * unit for unit.
+ * its default, Arabic, Hebrew, Hangul, Indic, Khmer and Myanmar shapers,
+ * glyph for glyph and unit for unit.
  *
  * What a font's shaping needs travels in a symbol file (its shaping
  * section), written by the build tool:
@@ -47,7 +47,8 @@
 enum { VEGA_SHAPING_HEADER = 80, VEGA_PLAN_BYTES = 144, VEGA_STEP_BYTES = 8, VEGA_PLAN_MASKS = 16,
        VEGA_PLAN_STAGES = 5 };
 enum { VEGA_SHAPE_LTR = 1, VEGA_SHAPE_RTL = 2 };
-enum { VEGA_SHAPER_DEFAULT, VEGA_SHAPER_ARABIC, VEGA_SHAPER_HEBREW, VEGA_SHAPER_HANGUL, VEGA_SHAPER_INDIC };
+enum { VEGA_SHAPER_DEFAULT, VEGA_SHAPER_ARABIC, VEGA_SHAPER_HEBREW, VEGA_SHAPER_HANGUL, VEGA_SHAPER_INDIC,
+       VEGA_SHAPER_KHMER, VEGA_SHAPER_MYANMAR };
 /* Plan flags: GPOS runs; mark advances are zeroed after it (by GDEF); glyph
  * classes come from Unicode (the font has none); the font positions marks
  * (a 'mark' feature); automatic fractions; the kern table kerns; marks are
@@ -63,6 +64,8 @@ enum { VEGA_MASK_ISOL = VEGA_MASK_SHAPER, VEGA_MASK_FINA, VEGA_MASK_FIN2, VEGA_M
 enum { VEGA_MASK_LJMO = VEGA_MASK_SHAPER, VEGA_MASK_VJMO, VEGA_MASK_TJMO };      /* Hangul */
 enum { VEGA_MASK_RPHF = VEGA_MASK_SHAPER, VEGA_MASK_PREF, VEGA_MASK_BLWF, VEGA_MASK_ABVF, VEGA_MASK_HALF,
        VEGA_MASK_PSTF, VEGA_MASK_INDIC_INIT };                                /* Indic */
+enum { VEGA_MASK_KHMER_PREF = VEGA_MASK_SHAPER, VEGA_MASK_KHMER_BLWF, VEGA_MASK_KHMER_ABVF, VEGA_MASK_KHMER_PSTF,
+       VEGA_MASK_KHMER_CFAR };                                                /* Khmer */
 /* The stages a plan names: Indic's, whose features decide a consonant's
  * position by whether they would substitute it. */
 enum { VEGA_STAGE_RPHF, VEGA_STAGE_PREF, VEGA_STAGE_BLWF, VEGA_STAGE_PSTF, VEGA_STAGE_VATU };