[ot] Keep substituted Default_Ignorables (#2886)

Don’t replace Default_Ignorables with zero-width space if they are
substituted or multiplied, not just when ligated.

After this change, HarfBuzz output matches that of Uniscribe and
CoreText for the new tests.

Fixes https://github.com/harfbuzz/harfbuzz/issues/2883

src/hb-ot-layout.hh

@@ -315,12 +315,13 @@ _hb_glyph_info_get_unicode_space_fallback_type (const hb_glyph_info_t *info)
 }
 
 static inline bool _hb_glyph_info_ligated (const hb_glyph_info_t *info);
+static inline bool _hb_glyph_info_substituted (const hb_glyph_info_t *info);
 
 static inline bool
 _hb_glyph_info_is_default_ignorable (const hb_glyph_info_t *info)
 {
   return (info->unicode_props() & UPROPS_MASK_IGNORABLE) &&
-	 !_hb_glyph_info_ligated (info);
+	 !_hb_glyph_info_substituted (info);
 }
 static inline bool
 _hb_glyph_info_is_default_ignorable_and_not_hidden (const hb_glyph_info_t *info)

test/shaping/data/in-house/tests/default-ignorables.tests

@@ -1,2 +1,5 @@
 ../fonts/051d92f8bc6ff724511b296c27623f824de256e9.ttf::U+0075,U+0361,U+034F,U+0301,U+0069:[gid2=0+1266|gid7=0@-617,442+0|gid5=0@-7,0+0|gid1=4+528]
 ../fonts/bf962d3202883a820aed019d9b5c1838c2ff69c6.ttf::U+0020,U+06CC,U+064E,U+034F,U+0651:[uni0651=1+0|space=1+0|uni064E=1@236,-432+0|uni06CC=1+1266|space=0+452]
+../fonts/6677074106f94a2644da6aaaacd5bbd48cbdc7de.ttf::U+0647,U+200D:[terminal=0+0|uni0647.init=0+702]
+../fonts/fcea341ba6489536390384d8403ce5287ba71a4a.ttf::U+0647,U+200D:[uni0647200D=0+702]
+../fonts/08b4b136f418add748dc641eb4a83033476f1170.ttf::U+0647,U+200D:[terminal=0+0|terminal=0+0|uni0647.init=0+702]

test/shaping/data/in-house/tests/mongolian-variation-selector.tests

@@ -16,4 +16,4 @@
 ../fonts/4d4206e30b2dbf1c1ef492a8eae1c9e7829ebad8.ttf::U+1820,U+200C,U+182D,U+1820,U+1837:[uni1820.E820_a.isol=0+1550|space=1+0|uni182D.E8E2_g.init=2+1000|uni1820.E823_a.medi=3+400|uni1837.E931_r.fina=4+750]
 ../fonts/4d4206e30b2dbf1c1ef492a8eae1c9e7829ebad8.ttf::U+1830,U+1824,U+1837,U+200D,U+200D,U+182D,U+1820,U+200D:[uni1830.E90B_s.init=0+850|uni1824.E844_u.medi=1+600|uni1837.E930_r.medi=2+600|space=2+0|space=2+0|uni182D.E8E5_g.medi1=5+800|uni1820.E823_a.medi=6+400|space=6+0]
 ../fonts/4d4206e30b2dbf1c1ef492a8eae1c9e7829ebad8.ttf::U+200D,U+182D,U+1824,U+182F,U+1822:[space=0+0|uni182D.E8E5_g.medi1=1+800|uni1824.E844_u.medi=2+600|uni182F.E908_l.medi=3+400|uni1822.E837_i.fina=4+600]
-../fonts/4d4206e30b2dbf1c1ef492a8eae1c9e7829ebad8.ttf::U+182A,U+1820,U+1822,U+182D,U+180E,U+1820,U+202F,U+1836,U+1822,U+1828:[uni182A1820.E875_ba.init=0+1000|uni1822.E836_i.medi2=2+1000|uni182D.E8E8_g.fina1=3+1250|space=4+0|uni1820.E827_a.fina2=5+600|uni202F.nobreak=6+500|uni1836.E92B_y.init1=7+500|uni1822.E834_i.medi=8+500|uni1828.E866_n.fina=9+850]
+../fonts/4d4206e30b2dbf1c1ef492a8eae1c9e7829ebad8.ttf::U+182A,U+1820,U+1822,U+182D,U+180E,U+1820,U+202F,U+1836,U+1822,U+1828:[uni182A1820.E875_ba.init=0+1000|uni1822.E836_i.medi2=2+1000|uni182D.E8E8_g.fina1=3+1250|uni180E.E80E_mvs=4+0|uni1820.E827_a.fina2=5+600|uni202F.nobreak=6+500|uni1836.E92B_y.init1=7+500|uni1822.E834_i.medi=8+500|uni1828.E866_n.fina=9+850]