[truetype] Reset cvt and storage in context load.

Currently the cvt and storage are saved and restored in `TT_RunIns`.
However, this is too granular as the cvt and storage area should be set to
the original cvt and storage area only when setting up the hinting context.
This allows for the cvt and storage area to be modified while parsing
multiple glyphs, as is the case with composite glyphs.

* src/truetype/ttinterp.h (TT_ExecContextRec): Remove `origCvt` and
`origStorage`.

* src/truetype/ttinterp.c (TT_RunIns): Don't save and restore the cvt and
storage area.
(Modify_CVT_Check, Ins_WS): Switch from "if in glyph and using original data
do copy on write" to "if in glyph and not using glyph specific data do copy
on write".

src/truetype/ttinterp.c

@@ -1527,9 +1527,8 @@
   static void
   Modify_CVT_Check( TT_ExecContext  exc )
   {
-    /* TT_RunIns sets origCvt and restores cvt to origCvt when done. */
     if ( exc->iniRange == tt_coderange_glyph &&
-         exc->cvt == exc->origCvt            )
+         exc->cvt != exc->glyfCvt            )
     {
       exc->error = Update_Max( exc->memory,
                                &exc->glyfCvtSize,
@@ -3115,10 +3114,8 @@
     }
     else
     {
-      /* TT_RunIns sets origStorage and restores storage to origStorage */
-      /* when done.                                                     */
       if ( exc->iniRange == tt_coderange_glyph &&
-           exc->storage == exc->origStorage    )
+           exc->storage != exc->glyfStorage    )
       {
         FT_ULong  tmp = (FT_ULong)exc->glyfStoreSize;
 
@@ -7832,8 +7829,6 @@
       exc->func_move_cvt  = Move_CVT;
     }
 
-    exc->origCvt     = exc->cvt;
-    exc->origStorage = exc->storage;
     exc->iniRange    = exc->curRange;
 
     Compute_Funcs( exc );
@@ -8594,9 +8589,6 @@
                 ins_counter,
                 ins_counter == 1 ? "" : "s" ));
 
-    exc->cvt     = exc->origCvt;
-    exc->storage = exc->origStorage;
-
     return FT_Err_Ok;
 
   LErrorCodeOverflow_:
@@ -8606,9 +8598,6 @@
     if ( exc->error && !exc->instruction_trap )
       FT_TRACE1(( "  The interpreter returned error 0x%x\n", exc->error ));
 
-    exc->cvt     = exc->origCvt;
-    exc->storage = exc->origStorage;
-
     return exc->error;
   }
 

src/truetype/ttinterp.h

@@ -193,7 +193,6 @@ FT_BEGIN_HEADER
     FT_Long*           cvt;       /* ! */
     FT_ULong           glyfCvtSize;
     FT_Long*           glyfCvt;   /* cvt working copy for glyph */
-    FT_Long*           origCvt;
 
     FT_UInt            glyphSize; /* ! glyph instructions buffer size */
     FT_Byte*           glyphIns;  /* ! glyph instructions buffer      */
@@ -224,7 +223,6 @@ FT_BEGIN_HEADER
     FT_Long*           storage;      /* ! storage area            */
     FT_UShort          glyfStoreSize;
     FT_Long*           glyfStorage;  /* storage working copy for glyph */
-    FT_Long*           origStorage;
 
     FT_F26Dot6         period;     /* values used for the */
     FT_F26Dot6         phase;      /* `SuperRounding'     */