Fix off by one in would apply for chain context format 3 (#278)

* Fix off by one in would apply for chain context format 3

Also use the proper consonant check in the Indic shaper.

* Add test

---------

Co-authored-by: Behdad Esfahbod <[email protected]>

Author: dfrg

src/hb/ot/contextual.rs

@@ -413,12 +413,16 @@ impl WouldApply for ChainedSequenceContextFormat3<'_> {
         (!ctx.zero_context
             || (self.backtrack_coverage_offsets().is_empty()
                 && self.lookahead_coverage_offsets().is_empty()))
-            && (ctx.glyphs.len() == input_coverages.len() + 1
-                && input_coverages.iter().enumerate().all(|(i, coverage)| {
-                    coverage
-                        .map(|cov| cov.get(ctx.glyphs[i + 1]).is_some())
-                        .unwrap_or(false)
-                }))
+            && (ctx.glyphs.len() == input_coverages.len()
+                && input_coverages
+                    .iter()
+                    .skip(1)
+                    .enumerate()
+                    .all(|(i, coverage)| {
+                        coverage
+                            .map(|cov| cov.get(ctx.glyphs[i + 1]).is_some())
+                            .unwrap_or(false)
+                    }))
     }
 }
 

src/hb/ot_shaper_indic.rs

@@ -69,10 +69,6 @@ impl GlyphInfo {
         self.is_one_of(CONSONANT_FLAGS_INDIC)
     }
 
-    pub(crate) fn is_consonant_myanmar(&self) -> bool {
-        self.is_one_of(CONSONANT_FLAGS_MYANMAR)
-    }
-
     fn is_halant(&self) -> bool {
         self.is_one_of(rb_flag(ot_category_t::OT_H as u32))
     }
@@ -267,14 +263,6 @@ const CONSONANT_FLAGS_INDIC: u32 = category_flag(ot_category_t::OT_C)
     | category_flag(ot_category_t::OT_PLACEHOLDER)
     | category_flag(ot_category_t::OT_DOTTEDCIRCLE);
 
-const CONSONANT_FLAGS_MYANMAR: u32 = category_flag(ot_category_t::OT_C)
-    | category_flag(ot_category_t::OT_CS)
-    | category_flag(ot_category_t::OT_Ra)
-    // | category_flag(ot_category_t::OT_CM)
-    | category_flag(ot_category_t::IV)
-    | category_flag(ot_category_t::OT_GB)
-    | category_flag(ot_category_t::OT_DOTTEDCIRCLE);
-
 const JOINER_FLAGS: u32 =
     category_flag(ot_category_t::OT_ZWJ) | category_flag(ot_category_t::OT_ZWNJ);
 
@@ -890,7 +878,7 @@ fn initial_reordering_consonant_syllable(
             loop {
                 i -= 1;
                 // -> until a consonant is found
-                if buffer.info[i].is_consonant_myanmar() {
+                if buffer.info[i].is_consonant() {
                     // -> that does not have a below-base or post-base form
                     // (post-base forms have to follow below-base forms),
                     if buffer.info[i].indic_position() != ot_position_t::POS_BELOW_C

tests/fonts/in-house/755160ddba002332349fda3eb999e629d63dccf6.ttf

@@ -48547,6 +48547,18 @@ fn indic_malayalam_dot_reph_015() {
     );
 }
 
+#[test]
+fn indic_misc_002() {
+    assert_eq!(
+        shape(
+            "tests/fonts/in-house/755160ddba002332349fda3eb999e629d63dccf6.ttf",
+            "\u{0A2D}\u{0A4D}\u{0A30}\u{0A42}",
+            "",
+        ),
+        "[gid1=0+594|gid5=0+0|gid3=0+0]"
+    );
+}
+
 #[test]
 fn indic_old_spec_001() {
     assert_eq!(