[sfnt, truetype] Add `size_reset` to `MetricsVariations`.

This is a generalization of commit

```
commit e6699596af5c5d6f0ae0ea06e19df87dce088df8
Author: Werner Lemberg <wl@gnu.org>
Date:   Thu Feb 2 11:38:04 2017 +0100

    [truetype] Fix MVAR post-action handling.
```

It is also possible for plain `CFF ` style fonts to contain an `fvar` and
`MVAR` table and use `cff_metrics_adjust`.  `tt_size_reset` should only be
called with `TT_Size` and never with `CFF_Size`.

Allow the "metrics-variations" service to specify the correct function (if
any) to reset `FT_Size`s after adjusting metrics.

* src/truetype/ttobjs.c (tt_size_reset): Split off some functionality
into...
(tt_size_reset_height): ... this new function.

* src/truetype/ttdriver.c (tt_service_metrics_variations): Add
`size_reset`.
(tt_size_select, tt_size_request): Updated.

* src/truetype/ttobjs.h: Updated.

* include/freetype/internal/services/svmetric.h (MetricsVariations): Add
`size_reset`.
(FT_DEFINE_SERVICE_METRICSVARIATIONSREC): Updated.

* include/freetype/internal/tttypes.h (TT_FaceRec_): Rename `var` to
`tt_var` and add `face_var`.

* src/cff/cffdrivr.c (cff_service_metrics_variations): Add `size_reset`.
(cff_hadvance_adjust, cff_metrics_adjust): Updated.

* src/cff/cffobjs.c (cff_face_init): Use `face_var`.

* src/sfnt/sfobjs.c (sfnt_init_face): Initialize `face_var`.

* src/sfnt/ttmtx.c (tt_face_get_metrics): Use `tt_var`.

* src/truetype/ttgxvar.c (tt_size_reset_iterator): Renamed to...
(ft_size_reset_iterator): ... this new function.
Call `size_reset`.
(tt_apply_mvar): Pass `size_reset` to `ft_size_reset_iterator`.

Fixes #1211

1 files changed, 13 insertions, 10 deletions

diff --git a/src/truetype/ttgxvar.c b/src/truetype/ttgxvar.c
index 20d27ee42..3af028aac 100644
--- a/src/truetype/ttgxvar.c
+++ b/src/truetype/ttgxvar.c
@@ -1462,15 +1462,14 @@
 
 
   static FT_Error
-  tt_size_reset_iterator( FT_ListNode  node,
+  ft_size_reset_iterator( FT_ListNode  node,
                           void*        user )
   {
-    TT_Size  size = (TT_Size)node->data;
-
-    FT_UNUSED( user );
+    FT_Size                       size = (FT_Size)node->data;
+    FT_Service_MetricsVariations  var  = (FT_Service_MetricsVariations)user;
 
 
-    tt_size_reset( size, 1 );
+    var->size_reset( size );
 
     return FT_Err_Ok;
   }
@@ -1543,6 +1542,9 @@
 
     /* adjust all derived values */
     {
+      FT_Service_MetricsVariations  var =
+        (FT_Service_MetricsVariations)face->face_var;
+
       FT_Face  root = &face->root;
 
       /*
@@ -1584,11 +1586,12 @@
                                   face->postscript.underlineThickness / 2;
       root->underline_thickness = face->postscript.underlineThickness;
 
-      /* iterate over all FT_Size objects and call `tt_size_reset' */
-      /* to propagate the metrics changes                          */
-      FT_List_Iterate( &root->sizes_list,
-                       tt_size_reset_iterator,
-                       NULL );
+      /* iterate over all FT_Size objects and call `var->size_reset' */
+      /* to propagate the metrics changes                            */
+      if ( var && var->size_reset )
+        FT_List_Iterate( &root->sizes_list,
+                         ft_size_reset_iterator,
+                         (void*)var );
     }
   }