Correct decoder output table ordering

src/woff2_dec.cc

@@ -17,6 +17,7 @@
 #include "./woff2_dec.h"
 
 #include <stdlib.h>
+#include <algorithm>
 #include <complex>
 #include <cstring>
 #include <limits>
@@ -932,6 +933,24 @@ bool ConvertWOFF2ToTTF(uint8_t* result, size_t result_length,
     return FONT_COMPRESSION_FAILURE();
   }
 
+  // Re-order tables in output (OTSpec) order
+  if (header_version) {
+    // collection; we have to sort the table offset vector in each font
+    for (auto& ttc_font : ttc_fonts) {
+      std::map<uint32_t, uint16_t> sorted_index_by_tag;
+      for (auto table_index : ttc_font.table_indices) {
+        sorted_index_by_tag[tables[table_index].tag] = table_index;
+      }
+      uint16_t index = 0;
+      for (auto& i : sorted_index_by_tag) {
+        ttc_font.table_indices[index++] = i.second;
+      }
+    }
+  } else {
+    // non-collection; we can just sort the tables
+    std::sort(tables.begin(), tables.end());
+  }
+
   // Start building the font
   size_t offset = 0;
   size_t offset_table = 0;