[subset] sketch out support for a call that lists all codepoints present in a font. Implement support for it in format 4 cmap sub table.

src/hb-ot-cmap-table.hh

@@ -127,6 +127,13 @@ struct CmapSubtableFormat4
       return true;
     }
 
+    static inline void get_all_codepoints_func (const void *obj, hb_set_t *out)
+    {
+      const accelerator_t *thiz = (const accelerator_t *) obj;
+      for (unsigned int i = 0; i < thiz->segCount - 1; i++) // Skip the last segment (0xFFFF)
+	hb_set_add_range (out, thiz->startCount[i], thiz->endCount[i]);
+    }
+
     const HBUINT16 *endCount;
     const HBUINT16 *startCount;
     const HBUINT16 *idDelta;
@@ -667,21 +674,31 @@ struct cmap
 
       this->get_glyph_data = subtable;
       if (unlikely (symbol))
+      {
 	this->get_glyph_func = get_glyph_from_symbol<OT::CmapSubtable>;
-      else
+	this->get_all_codepoints_func = null_get_all_codepoints_func;
+      } else {
 	switch (subtable->u.format) {
 	/* Accelerate format 4 and format 12. */
-	default: this->get_glyph_func = get_glyph_from<OT::CmapSubtable>;		break;
+	default:
-	case 12: this->get_glyph_func = get_glyph_from<OT::CmapSubtableFormat12>;	break;
+	  this->get_glyph_func = get_glyph_from<OT::CmapSubtable>;
+	  this->get_all_codepoints_func = null_get_all_codepoints_func;
+	  break;
+	case 12:
+	  this->get_glyph_func = get_glyph_from<OT::CmapSubtableFormat12>;
+	  this->get_all_codepoints_func = null_get_all_codepoints_func;
+	  break;
 	case  4:
 	  {
 	    this->format4_accel.init (&subtable->u.format4);
 	    this->get_glyph_data = &this->format4_accel;
 	    this->get_glyph_func = this->format4_accel.get_glyph_func;
+	    this->get_all_codepoints_func = this->format4_accel.get_all_codepoints_func;
 	  }
 	  break;
 	}
       }
+    }
 
     inline void fini (void)
     {
@@ -710,10 +727,22 @@ struct cmap
       return get_nominal_glyph (unicode, glyph);
     }
 
+    inline void get_all_codepoints (hb_set_t *out) const
+    {
+      this->get_all_codepoints_func (get_glyph_data, out);
+    }
+
     protected:
     typedef bool (*hb_cmap_get_glyph_func_t) (const void *obj,
 					      hb_codepoint_t codepoint,
 					      hb_codepoint_t *glyph);
+    typedef void (*hb_cmap_get_all_codepoints_func_t) (const void *obj,
+						       hb_set_t *out);
+
+    static inline void null_get_all_codepoints_func (const void *obj, hb_set_t *out)
+    {
+      // NOOP
+    }
 
     template <typename Type>
     static inline bool get_glyph_from (const void *obj,
@@ -749,6 +778,8 @@ struct cmap
     private:
     hb_cmap_get_glyph_func_t get_glyph_func;
     const void *get_glyph_data;
+    hb_cmap_get_all_codepoints_func_t get_all_codepoints_func;
+
     OT::CmapSubtableFormat4::accelerator_t format4_accel;
 
     const OT::CmapSubtableFormat14 *uvs_table;

src/hb-subset.cc

@@ -371,3 +371,17 @@ hb_subset (hb_face_t *source,
   hb_subset_plan_destroy (plan);
   return result;
 }
+
+/**
+ * hb_subset_get_all_codepoints:
+ * @source: font face data to load.
+ * @out: set to add the all codepoints covered by font face, source.
+ */
+void
+hb_subset_get_all_codepoints (hb_face_t *source, hb_set_t *out)
+{
+  OT::cmap::accelerator_t cmap;
+  cmap.init (source);
+  cmap.get_all_codepoints (out);
+  cmap.fini();
+}

src/hb-subset.h

@@ -72,12 +72,15 @@ HB_EXTERN hb_bool_t *
 hb_subset_input_drop_hints (hb_subset_input_t *subset_input);
 
 /* hb_subset() */
-
 HB_EXTERN hb_face_t *
 hb_subset (hb_face_t *source,
 	   hb_subset_profile_t *profile,
            hb_subset_input_t *input);
 
+/* hb_subset_get_all_codepoints */
+HB_EXTERN void
+hb_subset_get_all_codepoints (hb_face_t *source, hb_set_t *out);
+
 HB_END_DECLS
 
 #endif /* HB_SUBSET_H */

test/api/Makefile.am

@@ -32,6 +32,7 @@ TEST_PROGS = \
 	test-set \
 	test-shape \
 	test-subset \
+	test-subset-codepoints \
 	test-subset-cmap \
 	test-subset-glyf \
 	test-subset-hdmx \
@@ -44,6 +45,7 @@ TEST_PROGS = \
 	$(NULL)
 
 test_subset_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
+test_subset_codepoints_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
 test_subset_cmap_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
 test_subset_glyf_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
 test_subset_hdmx_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la

test/api/test-subset-codepoints.c

@@ -0,0 +1,59 @@
+/*
+ * Copyright © 2018  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Google Author(s): Garret Rieger
+ */
+
+#include "hb-test.h"
+#include "hb-subset-test.h"
+
+static void
+test_get_all_codepoints_format4 (void)
+{
+  hb_face_t *face = hb_subset_test_open_font("fonts/Roboto-Regular.abc.format4.ttf");
+  hb_set_t *codepoints = hb_set_create();
+
+  hb_subset_get_all_codepoints (face, codepoints);
+
+  hb_codepoint_t cp = HB_SET_VALUE_INVALID;
+  g_assert (hb_set_next (codepoints, &cp));
+  g_assert_cmpuint (0x61, ==, cp);
+  g_assert (hb_set_next (codepoints, &cp));
+  g_assert_cmpuint (0x62, ==, cp);
+  g_assert (hb_set_next (codepoints, &cp));
+  g_assert_cmpuint (0x63, ==, cp);
+  g_assert (!hb_set_next (codepoints, &cp));
+
+  hb_set_destroy (codepoints);
+  hb_face_destroy (face);
+}
+
+int
+main (int argc, char **argv)
+{
+  hb_test_init (&argc, &argv);
+
+  hb_test_add (test_get_all_codepoints_format4);
+
+  return hb_test_run();
+}