Allow FT_ENCODING_NONE for `FT_Select_Charmap'.

This is a valid encoding tag for BDF, PCF, and Windows FNT, and
there is no reason to disallow it for these formats.

* src/base/ftobjs.c (FT_Select_Charmap): Implement it.

ChangeLog

@@ -1,3 +1,12 @@
+2018-07-17  Werner Lemberg  <wl@gnu.org>
+
+	Allow FT_ENCODING_NONE for `FT_Select_Charmap'.
+
+	This is a valid encoding tag for BDF, PCF, and Windows FNT, and
+	there is no reason to disallow it for these formats.
+
+	* src/base/ftobjs.c (FT_Select_Charmap): Implement it.
+
 2018-07-17  Werner Lemberg  <wl@gnu.org>
 
 	* src/pcf/pcfread.c (pcf_get_encodings): Trace `defaultChar'.

include/freetype/freetype.h

@@ -642,7 +642,8 @@ FT_BEGIN_HEADER
    *
    * @values:
    *   FT_ENCODING_NONE ::
-   *     The encoding value~0 is reserved.
+   *     The encoding value~0 is reserved for all formats except BDF, PCF,
+   *     and Windows FNT; see below for more information.
    *
    *   FT_ENCODING_UNICODE ::
    *     The Unicode character set.  This value covers all versions of

src/base/ftobjs.c

@@ -3480,7 +3480,8 @@
     if ( !face )
       return FT_THROW( Invalid_Face_Handle );
 
-    if ( encoding == FT_ENCODING_NONE )
+    /* FT_ENCODING_NONE is a valid encoding for BDF, PCF, and Windows FNT */
+    if ( encoding == FT_ENCODING_NONE && !face->num_charmaps )
       return FT_THROW( Invalid_Argument );
 
     /* FT_ENCODING_UNICODE is special.  We try to find the `best' Unicode */
@@ -3501,7 +3502,7 @@
       if ( cur[0]->encoding == encoding )
       {
         face->charmap = cur[0];
-        return 0;
+        return FT_Err_Ok;
       }
     }