[subset] CMAP table subsetting fix

Not all codepoints smaller than 0xFFFF go to cmap4 table.
Only subset codepoints existing in each table.
This will also make harfbuzz consistent with fontTools' behavior

src/hb-ot-cmap-table.hh

@@ -783,7 +783,7 @@ struct NonDefaultUVS : SortedArrayOf<UVSMapping, HBUINT32>
   {
     unsigned int count = len;
     for (unsigned int i = 0; i < count; i++)
-      out->add (arrayZ[i].glyphID);
+      out->add (arrayZ[i].unicodeValue);
   }
 
   void closure_glyphs (const hb_set_t      *unicodes,
@@ -977,6 +977,12 @@ struct CmapSubtableFormat14
     ;
   }
 
+  void collect_unicodes (hb_set_t *out) const
+  {
+    for (const VariationSelectorRecord& _ : record)
+      _.collect_unicodes (out, this);
+  }
+
   bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
@@ -1155,10 +1161,13 @@ struct cmap
 
     for (const EncodingRecord& _ : encodingrec_iter)
     {
+      hb_set_t unicodes_set;
+      (src_base+_.subtable).collect_unicodes (&unicodes_set);
+
       unsigned format = (src_base+_.subtable).u.format;
 
-      if (format == 4) c->copy (_, it, 4u, src_base, this, plan, &format4objidx);
-      else if (format == 12) c->copy (_, it, 12u, src_base, this, plan, &format12objidx);
+      if (format == 4) c->copy (_, + it | hb_filter (unicodes_set, hb_first), 4u, src_base, this, plan, &format4objidx);
+      else if (format == 12) c->copy (_, + it | hb_filter (unicodes_set, hb_first), 12u, src_base, this, plan, &format12objidx);
       else if (format == 14) c->copy (_, it, 14u, src_base, this, plan, &format14objidx);
     }
 

test/subset/data/Makefile.am

@@ -17,6 +17,7 @@ EXTRA_DIST += \
 	expected/layout.gpos2 \
 	expected/layout.gpos3 \
 	expected/layout.gsub6 \
+	expected/cmap \
 	expected/cmap14 \
 	expected/sbix \
 	expected/colr \

test/subset/data/Makefile.sources

@@ -9,6 +9,7 @@ TESTS = \
 	tests/layout.gpos2.tests \
 	tests/layout.gpos3.tests \
 	tests/layout.gsub6.tests \
+	tests/cmap.tests \
 	tests/cmap14.tests \
 	tests/sbix.tests \
 	tests/colr.tests \

test/subset/data/tests/cmap.tests

@@ -0,0 +1,16 @@
+FONTS:
+AdobeBlank-Regular.ttf
+
+PROFILES:
+default.txt
+drop-hints.txt
+drop-hints-retain-gids.txt
+retain-gids.txt
+name-ids.txt
+
+SUBSETS:
+ﻺ
+ﻹﻺ
+ﻦﻏ
+ab
+aﻺ