Fix cmap format 2 handling (#53320).

The patch introduced for #52646 was not correct.

* src/sfnt/ttcmap.c (tt_cmap2_char_next): Adjust condition.

ChangeLog

@@ -1,3 +1,11 @@
+2018-03-13  Werner Lemberg  <wl@gnu.org>
+
+	Fix cmap format 2 handling (#53320).
+
+	The patch introduced for #52646 was not correct.
+
+	* src/sfnt/ttcmap.c (tt_cmap2_char_next): Adjust condition.
+
 2018-03-10  Nikolaus Waxweiler  <madigens@gmail.com>
 
 	* CMakeLists.txt (BASE_SRCS): Update to changes from 2018-03-05.

src/sfnt/ttcmap.c

@@ -549,19 +549,18 @@
             }
           }
         }
+
+        /* if unsuccessful, avoid `charcode' leaving */
+        /* the current 256-character block           */
+        if ( count )
+          charcode--;
       }
 
-      /* If `charcode' is <= 0xFF, retry with `charcode + 1'.  If        */
-      /* `charcode' is 0x100 after the loop, do nothing since we have    */
-      /* just reached the first sub-header for two-byte character codes. */
-      /*                                                                 */
-      /* For all other cases, we jump to the next sub-header and adjust  */
-      /* `charcode' accordingly.                                         */
+      /* If `charcode' is <= 0xFF, retry with `charcode + 1'.      */
+      /* Otherwise jump to the next 256-character block and retry. */
     Next_SubHeader:
       if ( charcode <= 0xFF )
         charcode++;
-      else if ( charcode == 0x100 )
-        ;
       else
         charcode = FT_PAD_FLOOR( charcode, 0x100 ) + 0x100;
     }