[truetype] Fix MD instruction for twilight zone.

* src/truetype/ttinterp.c (Ins_MD): Without this fix, the MD
instruction applied to original coordinates of twilight points
always returns zero.

ChangeLog

@@ -1,3 +1,11 @@
+2011-10-25  Werner Lemberg  <wl@gnu.org>
+
+	[truetype] Fix MD instruction for twilight zone.
+
+	* src/truetype/ttinterp.c (Ins_MD): Without this fix, the MD
+	instruction applied to original coordinates of twilight points
+	always returns zero.
+
 2011-10-18  Werner Lemberg  <wl@gnu.org>
 
 	* Version 2.4.7 released.

src/truetype/ttinterp.c

@@ -5155,25 +5155,38 @@
         D = CUR_Func_project( CUR.zp0.cur + L, CUR.zp1.cur + K );
       else
       {
-        FT_Vector*  vec1 = CUR.zp0.orus + L;
-        FT_Vector*  vec2 = CUR.zp1.orus + K;
+        /* XXX: UNDOCUMENTED: twilight zone special case */
 
-
-        if ( CUR.metrics.x_scale == CUR.metrics.y_scale )
+        if ( CUR.GS.gep0 == 0 || CUR.GS.gep1 == 0 )
         {
-          /* this should be faster */
+          FT_Vector*  vec1 = CUR.zp0.org + L;
+          FT_Vector*  vec2 = CUR.zp1.org + K;
+
+
           D = CUR_Func_dualproj( vec1, vec2 );
-          D = TT_MULFIX( D, CUR.metrics.x_scale );
         }
         else
         {
-          FT_Vector  vec;
+          FT_Vector*  vec1 = CUR.zp0.orus + L;
+          FT_Vector*  vec2 = CUR.zp1.orus + K;
 
 
-          vec.x = TT_MULFIX( vec1->x - vec2->x, CUR.metrics.x_scale );
-          vec.y = TT_MULFIX( vec1->y - vec2->y, CUR.metrics.y_scale );
+          if ( CUR.metrics.x_scale == CUR.metrics.y_scale )
+          {
+            /* this should be faster */
+            D = CUR_Func_dualproj( vec1, vec2 );
+            D = TT_MULFIX( D, CUR.metrics.x_scale );
+          }
+          else
+          {
+            FT_Vector  vec;
 
-          D = CUR_fast_dualproj( &vec );
+
+            vec.x = TT_MULFIX( vec1->x - vec2->x, CUR.metrics.x_scale );
+            vec.y = TT_MULFIX( vec1->y - vec2->y, CUR.metrics.y_scale );
+
+            D = CUR_fast_dualproj( &vec );
+          }
         }
       }
     }