New Variation Font function `FT_Get_Default_Named_Instance`.

* include/freetype/ftmm.h, src/base/ftmm.c (FT_Get_Default_Named_Instance):
New function.

* include/freetype/internal/services/svmm.h
(FT_Get_Default_Named_Instance_Func): New typedef.
(FT_Service_MultiMasters): New field `get_default_named_instance`.
(FT_DEFINE_SERVICE_MULTIMASTERSREC): Updated.

* include/freetype/internal/tttypes.h (TT_Face): New field
`var_default_named_instance`.

* src/sfnt/sfobjc.s (sfnt_init_face): Initialize
`var_default_named_instance`.

* src/cff/cffdrivr.c (cff_get_default_named_instance): New function.
(cff_service_multi_masters): Updated.

* src/truetype/ttgxvar.c (TT_Get_MM_Var): Initialize
`var_default_named_instance`.
(TT_Get_Default_Named_Instance): New function.
* src/truetype/ttgxvar.h: Updated.
* src/truetype/ttdriver.c (tt_service_gx_multi_masters): Updated.

* src/type1/t1driver.c (t1_service_multi_masters): Updated.

* docs/CHANGES: Updated.

1 files changed, 39 insertions, 0 deletions

diff --git a/include/freetype/ftmm.h b/include/freetype/ftmm.h
index 3eabdd5f2..2c2f165fa 100644
--- a/include/freetype/ftmm.h
+++ b/include/freetype/ftmm.h
@@ -753,6 +753,45 @@ FT_BEGIN_HEADER
   FT_Set_Named_Instance( FT_Face  face,
                          FT_UInt  instance_index );
 
+
+  /**************************************************************************
+   *
+   * @function:
+   *   FT_Get_Default_Named_Instance
+   *
+   * @description:
+   *   Retrieve the index of the default named instance, to be used with
+   *   @FT_Set_Named_Instance.
+   *
+   *   The default instance of a variation font is that instance for which
+   *   the nth axis coordinate is equal to `axis[n].def` (as specified in the
+   *   @FT_MM_Var structure), with~n covering all axes.
+   *
+   *   FreeType synthesizes a named instance for the default instance if the
+   *   font does not contain such an entry.
+   *
+   * @input:
+   *   face ::
+   *     A handle to the source face.
+   *
+   * @output:
+   *   instance_index ::
+   *     The index of the default named instance.
+   *
+   * @return:
+   *   FreeType error code.  0~means success.
+   *
+   * @note:
+   *   For Adobe MM fonts (which don't have named instances) this function
+   *   always returns zero for `instance_index`.
+   *
+   * @since:
+   *   2.13.1
+   */
+  FT_EXPORT( FT_Error )
+  FT_Get_Default_Named_Instance( FT_Face   face,
+                                 FT_UInt  *instance_index );
+
   /* */