Document font structure layout constraints

The layout of the initial members of ftcrfont_info must match
ftfont_info

* src/ftcrfont.c (struct ftcrfont_info): Likewise.

* src/ftfont.c (struct ftfont_info): Document layout constraints.

2 files changed, 6 insertions, 4 deletions

diff --git a/src/ftcrfont.c b/src/ftcrfont.c
index 614ef083701..d19c300c5b0 100644
--- a/src/ftcrfont.c
+++ b/src/ftcrfont.c
@@ -35,8 +35,9 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 struct ftcrfont_info
 {
   struct font font;
-  /* The following six members must be here in this order to be
-     compatible with struct ftfont_info (in ftfont.c).  */
+  /* The following members up to and including 'matrix' must be here
+     in this order to be compatible with struct ftfont_info (in
+     ftfont.c).  */
 #ifdef HAVE_LIBOTF
   bool maybe_otf;         /* Flag to tell if this may be OTF or not.  */
   OTF *otf;
diff --git a/src/ftfont.c b/src/ftfont.c
index 8f048d2983b..a05aa12c2af 100644
--- a/src/ftfont.c
+++ b/src/ftfont.c
@@ -56,8 +56,9 @@ struct ftfont_info
 {
   struct font font;
 #ifdef HAVE_LIBOTF
-  /* The following four members must be here in this order to be
-     compatible with struct xftfont_info (in xftfont.c).  */
+  /* The following members up to and including 'matrix' must be here in
+     this order to be compatible with struct xftfont_info (in
+     xftfont.c).  */
   bool maybe_otf;       /* Flag to tell if this may be OTF or not.  */
   OTF *otf;
 #endif  /* HAVE_LIBOTF */