[sfnt] Support sbix graphicType 'flip'.

* src/sfnt/ttsbit.c (tt_face_load_sbix_image): Currently undocumented by
Apple, this flips the bitmap data horizontally.  It is used on macOS in
Apple Color Emoji; 19.4d6e1; 2024-02-05 (file `Apple Color Emoji.ttc`).

Fixes issue #1282.

src/sfnt/ttsbit.c

@@ -1462,6 +1462,7 @@
     FT_Int    originOffsetX, originOffsetY;
     FT_Tag    graphicType;
     FT_Int    recurse_depth = 0;
+    FT_Bool   flipped       = FALSE;
 
     FT_Error  error;
     FT_Byte*  p;
@@ -1517,12 +1518,17 @@
 
     switch ( graphicType )
     {
+    case FT_MAKE_TAG( 'f', 'l', 'i', 'p' ):
     case FT_MAKE_TAG( 'd', 'u', 'p', 'e' ):
       if ( recurse_depth < 4 )
       {
         glyph_index = FT_GET_USHORT();
         FT_FRAME_EXIT();
         recurse_depth++;
+
+        if ( graphicType == FT_MAKE_TAG( 'f', 'l', 'i', 'p' ) )
+          flipped = TRUE;
+
         goto retry;
       }
       error = FT_THROW( Invalid_File_Format );
@@ -1540,6 +1546,42 @@
                              glyph_end - glyph_start - 8,
                              TRUE,
                              metrics_only );
+      if ( !error && flipped )
+      {
+        FT_UInt32*  curr_pos = (FT_UInt32*)map->buffer;
+
+        /* `Load_SBit_Png` always returns a pixmap with 32 bits per pixel */
+        /* and no extra pitch bytes.                                      */
+        FT_UInt32  width      = (FT_UInt32)( map->width );
+        FT_UInt32  half_width = (FT_UInt32)( map->width / 2 );
+
+        FT_UInt  y;
+
+
+        for ( y = 0; y < map->rows; y++ )
+        {
+          FT_UInt32*  left  = curr_pos;
+          FT_UInt32*  right = curr_pos + width - 1;
+
+          FT_UInt32  x;
+
+
+          for ( x = 0; x < half_width; x++ )
+          {
+            FT_UInt32  value;
+
+
+            value  = *right;
+            *right = *left;
+            *left  = value;
+
+            left++;
+            right--;
+          }
+
+          curr_pos += width;
+        }
+      }
 #else
       error = FT_THROW( Unimplemented_Feature );
 #endif