+_populate_unicodes_to_retain (const hb_set_t *unicodes,
+ const hb_set_t *glyphs,
+ hb_subset_plan_t *plan)
+{
+ OT::cmap::accelerator_t cmap (plan->source);
+
+ constexpr static const int size_threshold = 4096;
+
+ if (glyphs->is_empty () && unicodes->get_population () < size_threshold)
+ {
+ /* This is the fast path if it's anticipated that size of unicodes
+ * is << than the number of codepoints in the font. */
+ for (hb_codepoint_t cp : *unicodes)
+ {
+ hb_codepoint_t gid;
+ if (!cmap.get_nominal_glyph (cp, &gid))
+ {
+ DEBUG_MSG(SUBSET, nullptr, "Drop U+%04X; no gid", cp);
+ continue;
+ }
+
+ plan->codepoint_to_glyph->set (cp, gid);
+ }
+ }
+ else
+ {
+ hb_map_t unicode_glyphid_map;
+ cmap.collect_mapping (hb_set_get_empty (), &unicode_glyphid_map);
+
+ for (hb_pair_t<hb_codepoint_t, hb_codepoint_t> cp_gid :
+ + unicode_glyphid_map.iter ())
+ {
+ if (!unicodes->has (cp_gid.first) && !glyphs->has (cp_gid.second))
+ continue;
+
+ plan->codepoint_to_glyph->set (cp_gid.first, cp_gid.second);
+ }
+
+ /* Add gids which where requested, but not mapped in cmap */
+ // TODO(garretrieger):
+ // Once https://github.com/harfbuzz/harfbuzz/issues/3169
+ // is implemented, this can be done with union and del_range
+ for (hb_codepoint_t gid : glyphs->iter ())
+ {
+ if (gid >= plan->source->get_num_glyphs ())
+ break;
+ plan->_glyphset_gsub->add (gid);
+ }
+ }
+
+ + plan->codepoint_to_glyph->keys () | hb_sink (plan->unicodes);
+ + plan->codepoint_to_glyph->values () | hb_sink (plan->_glyphset_gsub);
+}
+
+static void