[truetype] Fix copy-and-paste error (#56409).

* src/truetype/ttgload.c (load_truetype_glyph): Use correct indices
into `unrounded' array for phantom points.

ChangeLog

@@ -1,3 +1,10 @@
+2019-05-26  Ben Wagner  <bungeman@google.com>
+
+	[truetype] Fix copy-and-paste error (#56409).
+
+	* src/truetype/ttgload.c (load_truetype_glyph): Use correct indices
+	into `unrounded' array for phantom points.
+
 2019-05-29  Werner Lemberg  <wl@gnu.org>
 
 	[truetype] Fix 32bit builds (#56404).

src/truetype/ttgload.c

@@ -2018,11 +2018,13 @@
         /* recalculate linear horizontal and vertical advances */
         /* if we don't have HVAR and VVAR, respectively        */
         if ( !( face->variation_support & TT_FACE_FLAG_VAR_HADVANCE ) )
-          loader->linear = FT_PIX_ROUND( unrounded[1].x -
-                                         unrounded[0].x ) / 64;
+          loader->linear =
+            FT_PIX_ROUND( unrounded[outline.n_points - 3].x -
+                          unrounded[outline.n_points - 4].x ) / 64;
         if ( !( face->variation_support & TT_FACE_FLAG_VAR_VADVANCE ) )
-          loader->vadvance = FT_PIX_ROUND( unrounded[3].x -
-                                           unrounded[2].x ) / 64;
+          loader->vadvance =
+            FT_PIX_ROUND( unrounded[outline.n_points - 1].x -
+                          unrounded[outline.n_points - 2].x ) / 64;
 
       Exit1:
         FT_FREE( outline.points );