[freetype2] gsoc-craig-2023 6650b9ebc: Make find_unicode_charmap public and use it to choose the best charmap for building the reverse character map

[Werner Lemberg]

branch: gsoc-craig-2023
commit 6650b9ebc70a7629efd4f3ddcebe9e51e708e2de
Author: Craig White <gerzytet@gmail.com>
Commit: Craig White <gerzytet@gmail.com>

    Make find_unicode_charmap public and use it to choose the best charmap for 
building the reverse character map
---
 include/freetype/internal/ftobjs.h | 20 ++++++++++++++++++++
 src/autofit/afadjust.c             | 23 +++++++----------------
 src/base/ftobjs.c                  | 16 +---------------
 3 files changed, 28 insertions(+), 31 deletions(-)

diff --git a/include/freetype/internal/ftobjs.h 
b/include/freetype/internal/ftobjs.h
index 28bc9b65f..ceb4251df 100644
--- a/include/freetype/internal/ftobjs.h
+++ b/include/freetype/internal/ftobjs.h
@@ -275,6 +275,26 @@ FT_BEGIN_HEADER
                   FT_GlyphSlot    slot,
                   FT_Render_Mode  mode );
 
+  /**************************************************************************
+   *
+   * @Function:
+   *   find_unicode_charmap
+   *
+   * @Description:
+   *   This function finds a Unicode charmap, if there is one.
+   *   And if there is more than one, it tries to favour the more
+   *   extensive one, i.e., one that supports UCS-4 against those which
+   *   are limited to the BMP ( UCS-2 encoding.)
+   *
+   *   If a unicode charmap is found, face->charmap is set to it.
+   *
+   *   This function is called from open_face(),
+   *   from FT_Select_Charmap( ..., FT_ENCODING_UNICODE ),
+   *   and also from afadjust.c in the autofit module.
+   */
+  FT_BASE( FT_Error )
+  find_unicode_charmap( FT_Face  face );
+
 #ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
 
   typedef void  (*FT_Bitmap_LcdFilterFunc)( FT_Bitmap*      bitmap,
diff --git a/src/autofit/afadjust.c b/src/autofit/afadjust.c
index 78487f3f4..bf115d2b1 100644
--- a/src/autofit/afadjust.c
+++ b/src/autofit/afadjust.c
@@ -121,27 +121,17 @@ af_reverse_character_map_new( FT_Face face, 
AF_ReverseCharacterMap *map, FT_Memo
     /* Search for a unicode charmap */
     /* If there isn't one, create a blank map */
 
-    /*TODO: change this to logic that searches for a "preferred" unicode 
charmap that maps the most codepoints*/
-    /*see find_unicode_charmap*/
     /*TODO: use GSUB lookups    */
     FT_TRACE4(( "af_reverse_character_map_new: building reverse character 
map\n" ));
-    FT_CMap unicode_charmap = NULL;
-    for ( FT_UInt i = 0; i < face->num_charmaps; i++ )
-    {
-        if ( face->charmaps[i]->encoding == FT_ENCODING_UNICODE )
-        {
-            unicode_charmap = FT_CMAP( face->charmaps[i] );
-        }
-    }
 
-    if ( unicode_charmap == NULL )
-    {
+    FT_Error error;
+    /* backup face->charmap because find_unicode_charmap sets it */
+    FT_CharMap old_charmap = face->charmap;
+    if (( error = find_unicode_charmap( face ) )) {
         *map = NULL;
-        return FT_Err_Ok;
+        goto Exit;
     }
 
-    FT_Error error;
-
     if ( FT_NEW( *map ) )
     {
         goto Exit;
@@ -160,7 +150,7 @@ af_reverse_character_map_new( FT_Face face, 
AF_ReverseCharacterMap *map, FT_Memo
     for ( FT_Int i = 0; i < AF_ADJUSTMENT_DATABASE_LENGTH; i++ )
     {
         FT_UInt32 codepoint = adjustment_database[i].codepoint;
-        FT_Int glyph = unicode_charmap->clazz->char_index(unicode_charmap, 
codepoint);
+        FT_Int glyph = FT_Get_Char_Index( face, codepoint );
         if ( glyph == 0 )
         {
 #ifdef FT_DEBUG_LEVEL_TRACE
@@ -183,6 +173,7 @@ af_reverse_character_map_new( FT_Face face, 
AF_ReverseCharacterMap *map, FT_Memo
     ( *map )->length = size;
 
 Exit:
+    face->charmap = old_charmap;
     if ( error )
     {
         FT_TRACE4(( "    error while building reverse character map.  Using 
blank map.\n" ));
diff --git a/src/base/ftobjs.c b/src/base/ftobjs.c
index b379868ba..38f974473 100644
--- a/src/base/ftobjs.c
+++ b/src/base/ftobjs.c
@@ -1358,21 +1358,7 @@
                       driver );
   }
 
-  /**************************************************************************
-   *
-   * @Function:
-   *   find_unicode_charmap
-   *
-   * @Description:
-   *   This function finds a Unicode charmap, if there is one.
-   *   And if there is more than one, it tries to favour the more
-   *   extensive one, i.e., one that supports UCS-4 against those which
-   *   are limited to the BMP (said UCS-2 encoding.)
-   *
-   *   This function is called from open_face() (just below), and also
-   *   from FT_Select_Charmap( ..., FT_ENCODING_UNICODE ).
-   */
-  static FT_Error
+  FT_Error
   find_unicode_charmap( FT_Face  face )
   {
     FT_CharMap*  first;