Merge pull request #842 from googlefonts/maxp

[subset] when dropping hints, clear hint related fields in maxp.

src/hb-ot-maxp-table.hh

@@ -39,9 +39,39 @@ namespace OT {
 
 #define HB_OT_TAG_maxp HB_TAG('m','a','x','p')
 
+struct maxpV1Tail
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this));
+  }
+
+  HBUINT16 maxPoints;		  /* Maximum points in a non-composite glyph. */
+  HBUINT16 maxContours;		  /* Maximum contours in a non-composite glyph. */
+  HBUINT16 maxCompositePoints;	  /* Maximum points in a composite glyph. */
+  HBUINT16 maxCompositeContours;  /* Maximum contours in a composite glyph. */
+  HBUINT16 maxZones;		  /* 1 if instructions do not use the twilight zone (Z0),
+				   * or 2 if instructions do use Z0; should be set to 2 in
+				   * most cases. */
+  HBUINT16 maxTwilightPoints;	  /* Maximum points used in Z0. */
+  HBUINT16 maxStorage;		  /* Number of Storage Area locations. */
+  HBUINT16 maxFunctionDefs;	  /* Number of FDEFs, equal to the highest function number + 1. */
+  HBUINT16 maxInstructionDefs;	  /* Number of IDEFs. */
+  HBUINT16 maxStackElements;	  /* Maximum stack depth. (This includes Font and CVT
+				   * Programs, as well as the instructions for each glyph.) */
+  HBUINT16 maxSizeOfInstructions; /* Maximum byte count for glyph instructions. */
+  HBUINT16 maxComponentElements;  /* Maximum number of components referenced at
+				   * "top level" for any composite glyph. */
+  HBUINT16 maxComponentDepth;	  /* Maximum levels of recursion; 1 for simple components. */
+ public:
+  DEFINE_SIZE_STATIC (26);
+};
+
+
 struct maxp
 {
-  static const hb_tag_t tableTag	= HB_OT_TAG_maxp;
+  static const hb_tag_t tableTag = HB_OT_TAG_maxp;
 
   inline unsigned int get_num_glyphs (void) const
   {
@@ -56,9 +86,15 @@ struct maxp
   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
-    return_trace (c->check_struct (this) &&
-		  likely (version.major == 1 ||
-			  (version.major == 0 && version.minor == 0x5000u)));
+    if (unlikely (!c->check_struct (this)))
+      return_trace (false);
+
+    if (version.major == 1)
+    {
+      const maxpV1Tail &v1 = StructAfter<maxpV1Tail> (*this);
+      return v1.sanitize (c);
+    }
+    return_trace (likely (version.major == 0 && version.minor == 0x5000u));
   }
 
   inline bool subset (hb_subset_plan_t *plan) const
@@ -73,17 +109,34 @@ struct maxp
     OT::maxp *maxp_prime = (OT::maxp *) hb_blob_get_data (maxp_prime_blob, nullptr);
 
     maxp_prime->set_num_glyphs (plan->gids_to_retain_sorted.len);
+    if (plan->drop_hints)
+      drop_hint_fields (plan, maxp_prime);
 
     bool result = hb_subset_plan_add_table(plan, HB_OT_TAG_maxp, maxp_prime_blob);
     hb_blob_destroy (maxp_prime_blob);
     return result;
   }
 
-  /* We only implement version 0.5 as none of the extra fields in version 1.0 are useful. */
+  static inline void drop_hint_fields (hb_subset_plan_t *plan, OT::maxp *maxp_prime)
+  {
+    if (maxp_prime->version.major == 1)
+    {
+      maxpV1Tail &v1 = StructAfter<maxpV1Tail> (*maxp_prime);
+      v1.maxZones.set (1);
+      v1.maxTwilightPoints.set (0);
+      v1.maxStorage.set (0);
+      v1.maxFunctionDefs.set (0);
+      v1.maxInstructionDefs.set (0);
+      v1.maxStackElements.set (0);
+      v1.maxSizeOfInstructions.set (0);
+    }
+  }
+
   protected:
   FixedVersion<>version;		/* Version of the maxp table (0.5 or 1.0),
 					 * 0x00005000u or 0x00010000u. */
   HBUINT16	numGlyphs;		/* The number of glyphs in the font. */
+/*maxpV1Tail v1Tail[VAR]; */
   public:
   DEFINE_SIZE_STATIC (6);
 };

test/api/test-subset-glyf.c

@@ -31,14 +31,30 @@
 
 /* Unit tests for hb-subset-glyf.h */
 
-static void check_maxp_num_glyphs (hb_face_t *face, uint16_t expected_num_glyphs)
+static void check_maxp_field (uint8_t *raw_maxp, unsigned int offset, uint16_t expected_value)
+{
+  uint16_t actual_value = (raw_maxp[offset] << 8) + raw_maxp[offset + 1];
+  g_assert_cmpuint(expected_value, ==, actual_value);
+}
+
+static void check_maxp_num_glyphs (hb_face_t *face, uint16_t expected_num_glyphs, bool hints)
 {
   hb_blob_t *maxp_blob = hb_face_reference_table (face, HB_TAG ('m','a','x', 'p'));
 
   unsigned int maxp_len;
   uint8_t *raw_maxp = (uint8_t *) hb_blob_get_data(maxp_blob, &maxp_len);
-  uint16_t num_glyphs = (raw_maxp[4] << 8) + raw_maxp[5];
-  g_assert_cmpuint(expected_num_glyphs, ==, num_glyphs);
+
+  check_maxp_field (raw_maxp, 4, expected_num_glyphs); // numGlyphs
+  if (!hints)
+  {
+    check_maxp_field (raw_maxp, 14, 1); // maxZones
+    check_maxp_field (raw_maxp, 16, 0); // maxTwilightPoints
+    check_maxp_field (raw_maxp, 18, 0); // maxStorage
+    check_maxp_field (raw_maxp, 20, 0); // maxFunctionDefs
+    check_maxp_field (raw_maxp, 22, 0); // maxInstructionDefs
+    check_maxp_field (raw_maxp, 24, 0); // maxStackElements
+    check_maxp_field (raw_maxp, 26, 0); // maxSizeOfInstructions
+  }
 
   hb_blob_destroy (maxp_blob);
 }
@@ -57,7 +73,7 @@ test_subset_glyf (void)
 
   hb_subset_test_check (face_ac, face_abc_subset, HB_TAG ('g','l','y','f'));
   hb_subset_test_check (face_ac, face_abc_subset, HB_TAG ('l','o','c', 'a'));
-  check_maxp_num_glyphs(face_abc_subset, 3);
+  check_maxp_num_glyphs(face_abc_subset, 3, true);
 
   hb_face_destroy (face_abc_subset);
   hb_face_destroy (face_abc);
@@ -77,7 +93,7 @@ test_subset_glyf_with_components (void)
 
   hb_subset_test_check (face_subset, face_generated_subset, HB_TAG ('g','l','y','f'));
   hb_subset_test_check (face_subset, face_generated_subset, HB_TAG ('l','o','c', 'a'));
-  check_maxp_num_glyphs(face_generated_subset, 4);
+  check_maxp_num_glyphs(face_generated_subset, 4, true);
 
   hb_face_destroy (face_generated_subset);
   hb_face_destroy (face_subset);
@@ -98,7 +114,7 @@ test_subset_glyf_noop (void)
 
   hb_subset_test_check (face_abc, face_abc_subset, HB_TAG ('g','l','y','f'));
   hb_subset_test_check (face_abc, face_abc_subset, HB_TAG ('l','o','c', 'a'));
-  check_maxp_num_glyphs(face_abc_subset, 4);
+  check_maxp_num_glyphs(face_abc_subset, 4, true);
 
   hb_face_destroy (face_abc_subset);
   hb_face_destroy (face_abc);
@@ -120,7 +136,7 @@ test_subset_glyf_strip_hints (void)
 
   hb_subset_test_check (face_ac, face_abc_subset, HB_TAG ('l','o','c', 'a'));
   hb_subset_test_check (face_ac, face_abc_subset, HB_TAG ('g','l','y','f'));
-  check_maxp_num_glyphs(face_abc_subset, 3);
+  check_maxp_num_glyphs(face_abc_subset, 3, false);
 
   hb_face_destroy (face_abc_subset);
   hb_face_destroy (face_abc);