[subset] Add drop_ot_layout setting to subset input.

src/hb-subset-input.cc

@@ -45,6 +45,7 @@ hb_subset_input_create_or_fail (void)
 
   input->unicodes = hb_set_create ();
   input->glyphs = hb_set_create ();
+  input->drop_ot_layout = true;
 
   return input;
 }
@@ -117,3 +118,19 @@ hb_subset_input_drop_hints (hb_subset_input_t *subset_input)
 {
   return &subset_input->drop_hints;
 }
+
+/**
+ * hb_subset_input_drop_ot_layout:
+ * @subset_input: a subset_input.
+ *
+ * If enabled ot layout tables will be dropped as part of
+ * the subsetting operation. Currently this defaults to
+ * true.
+ *
+ * Since: 1.8.0
+ **/
+HB_EXTERN hb_bool_t *
+hb_subset_input_drop_ot_layout (hb_subset_input_t *subset_input)
+{
+  return &subset_input->drop_ot_layout;
+}

src/hb-subset-plan.cc

@@ -131,6 +131,7 @@ hb_subset_plan_create (hb_face_t           *face,
   hb_subset_plan_t *plan = hb_object_create<hb_subset_plan_t> ();
 
   plan->drop_hints = input->drop_hints;
+  plan->drop_ot_layout = input->drop_ot_layout;
   plan->unicodes = hb_set_create();
   plan->glyphs.init();
   plan->source = hb_face_reference (face);

src/hb-subset-plan.hh

@@ -41,6 +41,7 @@ struct hb_subset_plan_t
   ASSERT_POD ();
 
   hb_bool_t drop_hints;
+  hb_bool_t drop_ot_layout;
 
   // For each cp that we'd like to retain maps to the corresponding gid.
   hb_set_t *unicodes;

src/hb-subset-private.hh

@@ -44,6 +44,7 @@ struct hb_subset_input_t {
   hb_set_t *glyphs;
 
   hb_bool_t drop_hints;
+  hb_bool_t drop_ot_layout;
   /* TODO
    *
    * features

src/hb-subset.cc

@@ -302,10 +302,11 @@ _should_drop_table(hb_subset_plan_t *plan, hb_tag_t tag)
     case HB_TAG ('h', 'd', 'm', 'x'): /* hint table, fallthrough */
     case HB_TAG ('V', 'D', 'M', 'X'): /* hint table, fallthrough */
       return plan->drop_hints;
-    // Drop Layout Tables until subsetting is supported.
+    // Drop Layout Tables if requested.
     case HB_TAG ('G', 'D', 'E', 'F'): /* temporary */
     case HB_TAG ('G', 'P', 'O', 'S'): /* temporary */
     case HB_TAG ('G', 'S', 'U', 'B'): /* temporary */
+      return plan->drop_ot_layout;
     // Drop these tables below by default, list pulled
     // from fontTools:
     case HB_TAG ('B', 'A', 'S', 'E'):

src/hb-subset.h

@@ -71,6 +71,9 @@ hb_subset_input_glyph_set (hb_subset_input_t *subset_input);
 HB_EXTERN hb_bool_t *
 hb_subset_input_drop_hints (hb_subset_input_t *subset_input);
 
+HB_EXTERN hb_bool_t *
+hb_subset_input_drop_ot_layout (hb_subset_input_t *subset_input);
+
 /* hb_subset() */
 HB_EXTERN hb_face_t *
 hb_subset (hb_face_t *source,