diff --git a/src/hb-buffer.cc b/src/hb-buffer.cc
index 44571da..ec29659 100644
--- a/src/hb-buffer.cc
+++ b/src/hb-buffer.cc
@@ -887,3 +887,79 @@
 }
 
 
+static int
+compare_info_codepoint (const hb_glyph_info_t *pa,
+			const hb_glyph_info_t *pb)
+{
+  return (int) pb->codepoint - (int) pa->codepoint;
+}
+
+static inline void
+normalize_glyphs_cluster (hb_buffer_t *buffer,
+			  unsigned int start,
+			  unsigned int end,
+			  bool backward)
+{
+  hb_glyph_position_t *pos = buffer->pos;
+
+  /* Total cluster advance */
+  hb_position_t total_x_advance = 0, total_y_advance = 0;
+  for (unsigned int i = start; i < end; i++)
+  {
+    total_x_advance += pos[i].x_advance;
+    total_y_advance += pos[i].y_advance;
+  }
+
+  hb_position_t x_advance = 0, y_advance = 0;
+  for (unsigned int i = start; i < end; i++)
+  {
+    pos[i].x_offset += x_advance;
+    pos[i].y_offset += y_advance;
+
+    x_advance += pos[i].x_advance;
+    y_advance += pos[i].y_advance;
+
+    pos[i].x_advance = 0;
+    pos[i].y_advance = 0;
+  }
+
+  if (backward)
+  {
+    /* Transfer all cluster advance to the last glyph. */
+    pos[end - 1].x_advance = total_x_advance;
+    pos[end - 1].y_advance = total_y_advance;
+
+    hb_bubble_sort (buffer->info + start, end - start - 1, compare_info_codepoint, buffer->pos + start);
+  } else {
+    /* Transfer all cluster advance to the first glyph. */
+    pos[start].x_advance += total_x_advance;
+    pos[start].y_advance += total_y_advance;
+    for (unsigned int i = start + 1; i < end; i++) {
+      pos[i].x_offset -= total_x_advance;
+      pos[i].y_offset -= total_y_advance;
+    }
+    hb_bubble_sort (buffer->info + start + 1, end - start - 1, compare_info_codepoint, buffer->pos + start + 1);
+  }
+}
+
+void
+hb_buffer_normalize_glyphs (hb_buffer_t *buffer)
+{
+  assert (buffer->have_positions);
+  /* XXX assert (buffer->have_glyphs); */
+
+  bool backward = HB_DIRECTION_IS_BACKWARD (buffer->props.direction);
+
+  unsigned int count = buffer->len;
+  if (unlikely (!count)) return;
+  hb_glyph_info_t *info = buffer->info;
+
+  unsigned int start = 0;
+  unsigned int end;
+  for (end = start + 1; end < count; end++)
+    if (info[start].cluster != info[end].cluster) {
+      normalize_glyphs_cluster (buffer, start, end, backward);
+      start = end;
+    }
+  normalize_glyphs_cluster (buffer, start, end, backward);
+}