Use functions to get new gids. Avoid 0; fonttools drops it from cmap.

src/hb-ot-cmap-table.hh

@@ -522,18 +522,25 @@ struct cmap
 		  encodingRecord.sanitize (c, this));
   }
 
-  inline void populate_groups(hb_prealloced_array_t<hb_codepoint_t> &codepoints,
-                              hb_prealloced_array_t<CmapSubtableLongGroup> *groups) const
+  inline hb_bool_t populate_groups(hb_subset_plan_t *plan,
+                                   hb_prealloced_array_t<CmapSubtableLongGroup> *groups) const
   {
     CmapSubtableLongGroup *group = nullptr;
-    for (unsigned int i = 0; i < codepoints.len; i++) {
-      hb_codepoint_t cp = codepoints[i];
+    for (unsigned int i = 0; i < plan->codepoints.len; i++) {
+
+      hb_codepoint_t cp = plan->codepoints[i];
       if (!group || cp - 1 != group->endCharCode)
       {
         group = groups->push();
         group->startCharCode.set(cp);
         group->endCharCode.set(cp);
-        group->glyphID.set(i);  // index in codepoints is new gid
+        hb_codepoint_t new_gid;
+        if (unlikely(!hb_subset_plan_new_gid_for_codepoint(plan, cp, &new_gid)))
+        {
+          DEBUG_MSG(SUBSET, nullptr, "Unable to find new gid for %04x", cp);
+          return false;
+        }
+        group->glyphID.set(new_gid);
       } else
       {
         group->endCharCode.set(cp);
@@ -545,6 +552,8 @@ struct cmap
       CmapSubtableLongGroup& group = (*groups)[i];
       DEBUG_MSG(SUBSET, nullptr, "  %d: U+%04X-U+%04X, gid %d-%d", i, (uint32_t) group.startCharCode, (uint32_t) group.endCharCode, (uint32_t) group.glyphID, (uint32_t) group.glyphID + ((uint32_t) group.endCharCode - (uint32_t) group.startCharCode));
     }
+
+    return true;
   }
 
   hb_bool_t _subset (hb_prealloced_array_t<CmapSubtableLongGroup> &groups,
@@ -600,7 +609,10 @@ struct cmap
   {
     hb_auto_array_t<CmapSubtableLongGroup> groups;
 
-    populate_groups(plan->codepoints, &groups);
+    if (unlikely(!populate_groups(plan, &groups)))
+    {
+      return nullptr;
+    }
 
     // We now know how big our blob needs to be
     // TODO use APIs from the structs to get size?

src/hb-subset-plan.cc

@@ -38,6 +38,24 @@ _hb_codepoint_t_cmp (const void *pa, const void *pb)
   return a < b ? -1 : a > b ? +1 : 0;
 }
 
+hb_bool_t
+hb_subset_plan_new_gid_for_codepoint (hb_subset_plan_t *plan,
+                                      hb_codepoint_t codepoint,
+                                      hb_codepoint_t *new_gid)
+{
+  // TODO actual map, delete this garbage.
+  for (unsigned int i = 0; i < plan->codepoints.len; i++)
+  {
+    if (plan->codepoints[i] != codepoint) continue;
+    if (!hb_subset_plan_new_gid_for_old_id(plan, plan->gids_to_retain[i], new_gid))
+    {
+      return false;
+    }
+    return true;
+  }
+  return false;
+}
+
 hb_bool_t
 hb_subset_plan_new_gid_for_old_id (hb_subset_plan_t *plan,
                                    hb_codepoint_t old_gid,
@@ -46,7 +64,8 @@ hb_subset_plan_new_gid_for_old_id (hb_subset_plan_t *plan,
   // the index in old_gids is the new gid; only up to codepoints.len are valid
   for (unsigned int i = 0; i < plan->gids_to_retain_sorted.len; i++) {
     if (plan->gids_to_retain_sorted[i] == old_gid) {
-      *new_gid = i;
+      // +1: assign new gids from 1..N; 0 is special
+      *new_gid = i + 1;
       return true;
     }
   }
@@ -109,10 +128,6 @@ _populate_gids_to_retain (hb_face_t *face,
     *(old_gids_sorted.push ()) = 0;
   old_gids_sorted.qsort (_hb_codepoint_t_cmp);
 
-  for (unsigned int i = 0; i < codepoints.len; i++) {
-      DEBUG_MSG(SUBSET, nullptr, " U+%04X, old_gid %d, new_gid %d", codepoints[i], old_gids[i], i);
-  }
-
   // TODO(Q1) expand with glyphs that make up complex glyphs
   // TODO expand with glyphs reached by G*
   //

src/hb-subset-plan.hh

@@ -55,6 +55,11 @@ hb_subset_plan_new_gid_for_old_id(hb_subset_plan_t *plan,
                                   hb_codepoint_t old_gid,
                                   hb_codepoint_t *new_gid /* OUT */);
 
+HB_INTERNAL hb_bool_t
+hb_subset_plan_new_gid_for_codepoint(hb_subset_plan_t *plan,
+                                     hb_codepoint_t codepont,
+                                     hb_codepoint_t *new_gid /* OUT */);
+
 HB_INTERNAL void
 hb_subset_plan_destroy (hb_subset_plan_t *plan);
 

src/hb-subset.cc

@@ -124,7 +124,7 @@ _subset (hb_subset_plan_t *plan, hb_face_t *source)
     hb_blob_destroy (source_blob);
 
     hb_tag_t tag = TableType::tableTag;
-    DEBUG_MSG(SUBSET, nullptr, "Subset %c%c%c%c %s", HB_UNTAG(tag), result ? "success" : "FAILED!");
+    DEBUG_MSG(SUBSET, nullptr, "OT::%c%c%c%c::subset %s", HB_UNTAG(tag), result ? "success" : "FAILED!");
     return result;
 }