Don't magnify extent of shifts by variable glyph interpolation

* src/sfnt.c (sfnt_infer_deltas_2): Correctly index
x_coordinates and y_coordinates computing deltas for plain
shift.
(sfnt_vary_simple_glyph): Copy glyph contents to original_x and
original_y not the first time is create, but before each tuple
is applied.

1 files changed, 14 insertions, 8 deletions

diff --git a/src/sfnt.c b/src/sfnt.c
index e66292c6ad8..aa8b49a9ecd 100644
--- a/src/sfnt.c
+++ b/src/sfnt.c
@@ -15411,7 +15411,7 @@ sfnt_infer_deltas_2 (struct sfnt_glyph *glyph, size_t pair_start,
               d1 = (glyph->simple->x_coordinates[pair_start]
                     - x[pair_start]);
               d2 = (glyph->simple->x_coordinates[pair_end]
-                    - x[pair_start]);
+                    - x[pair_end]);
 
               if (d1 == d2)
                 glyph->simple->x_coordinates[j] += d1;
@@ -15483,7 +15483,7 @@ sfnt_infer_deltas_2 (struct sfnt_glyph *glyph, size_t pair_start,
               d1 = (glyph->simple->y_coordinates[pair_start]
                     - y[pair_start]);
               d2 = (glyph->simple->y_coordinates[pair_end]
-                    - y[pair_start]);
+                    - y[pair_end]);
 
               if (d1 == d2)
                 glyph->simple->y_coordinates[j] += d1;
@@ -15915,14 +15915,20 @@ sfnt_vary_simple_glyph (struct sfnt_blend *blend, sfnt_glyph id,
                                      * glyph->simple->number_of_points);
 
               original_y = original_x + glyph->simple->number_of_points;
-              memcpy (original_x, glyph->simple->x_coordinates,
-                      (sizeof *original_x
-                       * glyph->simple->number_of_points));
-              memcpy (original_y, glyph->simple->y_coordinates,
-                      (sizeof *original_y
-                       * glyph->simple->number_of_points));
             }
 
+          /* The array of original coordinates should reflect the
+             state of the glyph immediately before deltas from this
+             tuple are applied, in contrast to the state before any
+             deltas are applied.  */
+
+          memcpy (original_x, glyph->simple->x_coordinates,
+                  (sizeof *original_x
+                   * glyph->simple->number_of_points));
+          memcpy (original_y, glyph->simple->y_coordinates,
+                  (sizeof *original_y
+                   * glyph->simple->number_of_points));
+
           memset (touched, 0, (sizeof *touched
                                * glyph->simple->number_of_points));