[truetype] Correctly handle variation font phantom points (#52683).

* src/truetype/ttgxvar.c (TT_Vary_Apply_Glyph_Deltas): Fix phantom
point indices.

ChangeLog

@@ -1,3 +1,10 @@
+2017-12-17  Jonathan Kew  <jfkthame@gmail.com>
+
+	[truetype] Correctly handle variation font phantom points (#52683).
+
+	* src/truetype/ttgxvar.c (TT_Vary_Apply_Glyph_Deltas): Fix phantom
+	point indices.
+
 2017-12-17  Jonathan Kew  <jfkthame@gmail.com>
 
 	Fix incorrect advance width scaling (#52683).

src/truetype/ttgxvar.c

@@ -3630,7 +3630,7 @@
           FT_Pos  delta_y = FT_MulFix( deltas_y[j], apply );
 
 
-          if ( j < n_points - 3 )
+          if ( j < n_points - 4 )
           {
             outline->points[j].x += delta_x;
             outline->points[j].y += delta_y;
@@ -3640,25 +3640,25 @@
             /* To avoid double adjustment of advance width or height, */
             /* adjust phantom points only if there is no HVAR or VVAR */
             /* support, respectively.                                 */
-            if ( j == ( n_points - 3 )          &&
-                 !( face->variation_support   &
-                    TT_FACE_FLAG_VAR_HADVANCE ) )
+            if ( j == ( n_points - 4 )        &&
+                 !( face->variation_support &
+                    TT_FACE_FLAG_VAR_LSB    ) )
+              outline->points[j].x += delta_x;
+
+            else if ( j == ( n_points - 3 )          &&
+                      !( face->variation_support   &
+                         TT_FACE_FLAG_VAR_HADVANCE ) )
               outline->points[j].x += delta_x;
 
             else if ( j == ( n_points - 2 )        &&
                       !( face->variation_support &
-                         TT_FACE_FLAG_VAR_LSB    ) )
-              outline->points[j].x += delta_x;
+                         TT_FACE_FLAG_VAR_TSB    ) )
+              outline->points[j].y += delta_y;
 
             else if ( j == ( n_points - 1 )          &&
                       !( face->variation_support   &
                          TT_FACE_FLAG_VAR_VADVANCE ) )
               outline->points[j].y += delta_y;
-
-            else if ( j == ( n_points - 0 )        &&
-                      !( face->variation_support &
-                         TT_FACE_FLAG_VAR_TSB    ) )
-              outline->points[j].y += delta_y;
           }
 
 #ifdef FT_DEBUG_LEVEL_TRACE