[instance] instantiate fvar table

Added an old->new axes_indices mapping in the subset plan

src/hb-ot-var-fvar-table.hh

@@ -47,6 +47,44 @@ struct InstanceRecord
   hb_array_t<const HBFixed> get_coordinates (unsigned int axis_count) const
   { return coordinatesZ.as_array (axis_count); }
 
+  bool subset (hb_subset_context_t *c,
+               unsigned axis_count,
+               bool has_postscript_nameid) const
+  {
+    TRACE_SUBSET (this);
+    if (unlikely (!c->serializer->embed (subfamilyNameID))) return_trace (false);
+    if (unlikely (!c->serializer->embed (flags))) return_trace (false);
+
+    const hb_array_t<const HBFixed> coords = get_coordinates (axis_count);
+    const hb_hashmap_t<hb_tag_t, float> *axes_location = c->plan->user_axes_location;
+    for (unsigned i = 0 ; i < axis_count; i++)
+    {
+      unsigned *axis_tag;
+      // only keep instances whose coordinates == pinned axis location
+      if (!c->plan->axes_old_index_tag_map->has (i, &axis_tag)) continue;
+
+      if (axes_location->has (*axis_tag) &&
+          fabsf (axes_location->get (*axis_tag) - coords[i].to_float ()) > 0.001f)
+        return_trace (false);
+
+      if (!c->plan->axes_index_map->has (i))
+        continue;
+
+      if (!c->serializer->embed (coords[i]))
+        return_trace (false);
+    }
+
+    if (has_postscript_nameid)
+    {
+      NameID name_id;
+      name_id = StructAfter<NameID> (coords);
+      if (!c->serializer->embed (name_id))
+        return_trace (false);
+    }
+
+    return_trace (true);
+  }
+
   bool sanitize (hb_sanitize_context_t *c, unsigned int axis_count) const
   {
     TRACE_SANITIZE (this);
@@ -321,6 +359,48 @@ struct fvar
     }
   }
 
+  bool subset (hb_subset_context_t *c) const
+  {
+    TRACE_SUBSET (this);
+    unsigned retained_axis_count = c->plan->axes_index_map->get_population ();
+    if (!retained_axis_count) //all axes are pinned
+      return_trace (false);
+
+    fvar *out = c->serializer->embed (this);
+    if (unlikely (!out)) return_trace (false);
+
+    if (!c->serializer->check_assign (out->axisCount, retained_axis_count, HB_SERIALIZE_ERROR_INT_OVERFLOW))
+      return_trace (false);
+
+    bool has_postscript_nameid = false;
+    if (instanceSize >= axisCount * 4 + 6)
+      has_postscript_nameid = true;
+
+    if (!c->serializer->check_assign (out->instanceSize, retained_axis_count * 4 + (has_postscript_nameid ? 6 : 4),
+                                      HB_SERIALIZE_ERROR_INT_OVERFLOW))
+      return_trace (false);
+
+    auto axes_records = get_axes ();
+    for (unsigned i = 0 ; i < (unsigned)axisCount; i++)
+    {
+      if (!c->plan->axes_index_map->has (i)) continue;
+      if (unlikely (!c->serializer->embed (axes_records[i])))
+        return_trace (false);
+    }
+
+    if (!c->serializer->check_assign (out->firstAxis, get_size (), HB_SERIALIZE_ERROR_INT_OVERFLOW))
+      return_trace (false);
+
+    for (unsigned i = 0 ; i < (unsigned)instanceCount; i++)
+    {
+      const InstanceRecord *instance = get_instance (i);
+      auto snap = c->serializer->snapshot ();
+      if (!instance->subset (c, axisCount, has_postscript_nameid))
+        c->serializer->revert (snap);
+    }
+    return_trace (true);
+  }
+
   public:
   hb_array_t<const AxisRecord> get_axes () const
   { return hb_array (&(this+firstAxis), axisCount); }

src/hb-subset-input.cc

@@ -89,7 +89,6 @@ hb_subset_input_create_or_fail (void)
 
   hb_tag_t default_no_subset_tables[] = {
     HB_TAG ('a', 'v', 'a', 'r'),
-    HB_TAG ('f', 'v', 'a', 'r'),
     HB_TAG ('g', 'a', 's', 'p'),
     HB_TAG ('c', 'v', 't', ' '),
     HB_TAG ('f', 'p', 'g', 'm'),

src/hb-subset-plan.cc

@@ -663,18 +663,22 @@ _normalize_axes_location (hb_face_t *face, hb_subset_plan_t *plan)
     seg_maps = face->table.avar->get_segment_maps ();
 
   bool axis_not_pinned = false;
-  unsigned axis_count = 0;
+  unsigned old_axis_idx = 0, new_axis_idx = 0;
   for (const auto& axis : axes)
   {
     hb_tag_t axis_tag = axis.get_axis_tag ();
+    plan->axes_old_index_tag_map->set (old_axis_idx, axis_tag);
+
     if (!plan->user_axes_location->has (axis_tag))
     {
       axis_not_pinned = true;
+      plan->axes_index_map->set (old_axis_idx, new_axis_idx);
+      new_axis_idx++;
     }
     else
     {
       int normalized_v = axis.normalize_axis_value (plan->user_axes_location->get (axis_tag));
-      if (has_avar && axis_count < face->table.avar->get_axis_count ())
+      if (has_avar && old_axis_idx < face->table.avar->get_axis_count ())
       {
         normalized_v = seg_maps->map (normalized_v);
       }
@@ -685,7 +689,7 @@ _normalize_axes_location (hb_face_t *face, hb_subset_plan_t *plan)
     if (has_avar)
       seg_maps = &StructAfter<OT::SegmentMaps> (*seg_maps);
     
-    axis_count++;
+    old_axis_idx++;
   }
   plan->all_axes_pinned = !axis_not_pinned;
 }
@@ -755,6 +759,8 @@ hb_subset_plan_create_or_fail (hb_face_t	 *face,
   plan->check_success (plan->user_axes_location = hb_hashmap_create<hb_tag_t, float> ());
   if (plan->user_axes_location && input->axes_location)
       *plan->user_axes_location = *input->axes_location;
+  plan->check_success (plan->axes_index_map = hb_map_create ());
+  plan->check_success (plan->axes_old_index_tag_map = hb_map_create ());
   plan->all_axes_pinned = false;
   plan->pinned_at_default = true;
 

src/hb-subset-plan.hh

@@ -67,6 +67,8 @@ struct hb_subset_plan_t
     hb_map_destroy (gpos_features);
     hb_map_destroy (colrv1_layers);
     hb_map_destroy (colr_palettes);
+    hb_map_destroy (axes_index_map);
+    hb_map_destroy (axes_old_index_tag_map);
 
     hb_hashmap_destroy (gsub_langsys);
     hb_hashmap_destroy (gpos_langsys);
@@ -158,6 +160,10 @@ struct hb_subset_plan_t
   hb_hashmap_t<hb_tag_t, int> *axes_location;
   //user specified axes location map
   hb_hashmap_t<hb_tag_t, float> *user_axes_location;
+  //retained old axis index -> new axis index mapping in fvar axis array
+  hb_map_t *axes_index_map;
+  //axis_index->axis_tag mapping in fvar axis array
+  hb_map_t *axes_old_index_tag_map;
   bool all_axes_pinned;
   bool pinned_at_default;
 

src/hb-subset.cc

@@ -50,6 +50,7 @@
 #include "hb-ot-color-cbdt-table.hh"
 #include "hb-ot-layout-gsub-table.hh"
 #include "hb-ot-layout-gpos-table.hh"
+#include "hb-ot-var-fvar-table.hh"
 #include "hb-ot-var-gvar-table.hh"
 #include "hb-ot-var-hvar-table.hh"
 #include "hb-ot-math-table.hh"
@@ -475,6 +476,9 @@ _subset_table (hb_subset_plan_t *plan,
   case HB_OT_TAG_HVAR: return _subset<const OT::HVAR> (plan, buf);
   case HB_OT_TAG_VVAR: return _subset<const OT::VVAR> (plan, buf);
 #endif
+  case HB_OT_TAG_fvar:
+    if (plan->user_axes_location->is_empty ()) return _passthrough (plan, tag);
+    return _subset<const OT::fvar> (plan, buf);
   case HB_OT_TAG_STAT:
     /*TODO(qxliu): change the condition as we support more complex
      * instancing operation*/