[autofit] Restore OpenType feature check.

This was removed while rewriting the HarfBuzz interface.

* src/autofit/afglobal.h (AF_FaceGlobalsRec): Add `hb_buf' field to
hold internal HarfBuzz buffer, needed for feature comparison.

* src/autofit/afglobal.c (af_face_globals_new,
af_face_globals_free): Initialize and destroy `hb_buf'.

* src/autofit/afshaper.c (af_shaper_get_cluster): Compare character
(cluster) with and without applied feature.

* src/autofit/aflatin.c (af_latin_metrics_init_blues): Fix tracing
message.

ChangeLog

@@ -1,3 +1,21 @@
+2015-12-10  Werner Lemberg  <wl@gnu.org>
+
+	[autofit] Restore OpenType feature check.
+
+	This was removed while rewriting the HarfBuzz interface.
+
+	* src/autofit/afglobal.h (AF_FaceGlobalsRec): Add `hb_buf' field to
+	hold internal HarfBuzz buffer, needed for feature comparison.
+
+	* src/autofit/afglobal.c (af_face_globals_new,
+	af_face_globals_free): Initialize and destroy `hb_buf'.
+
+	* src/autofit/afshaper.c (af_shaper_get_cluster): Compare character
+	(cluster) with and without applied feature.
+
+	* src/autofit/aflatin.c (af_latin_metrics_init_blues): Fix tracing
+	message.
+
 2015-12-10  Werner Lemberg  <wl@gnu.org>
 
 	[autofit] Remove redundant code.

src/autofit/afglobal.c

@@ -364,6 +364,7 @@
 
 #ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
     globals->hb_font = hb_ft_font_create( face, NULL );
+    globals->hb_buf  = hb_buffer_create();
 #endif
 
     error = af_face_globals_compute_style_coverage( globals );
@@ -410,6 +411,9 @@
 #ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
       hb_font_destroy( globals->hb_font );
       globals->hb_font = NULL;
+
+      hb_buffer_destroy( globals->hb_buf );
+      globals->hb_buf = NULL;
 #endif
 
       globals->glyph_count               = 0;

src/autofit/afglobal.h

@@ -110,6 +110,7 @@ FT_BEGIN_HEADER
 
 #ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
     hb_font_t*       hb_font;
+    hb_buffer_t*     hb_buf;           /* for feature comparison */
 #endif
 
     /* per-face auto-hinter properties */

src/autofit/aflatin.c

@@ -396,6 +396,12 @@
 
         p = af_shaper_get_cluster( p, &metrics->root, shaper_buf, &num_idx );
 
+        if ( !num_idx )
+        {
+          FT_TRACE5(( "  U+%04lX unavailable\n", ch ));
+          continue;
+        }
+
         if ( AF_LATIN_IS_TOP_BLUE( bs ) )
           best_y_extremum = FT_INT_MIN;
         else

src/autofit/afshaper.c

@@ -466,7 +466,7 @@
     while ( *p == ' ' )
       p++;
 
-    /* count characters up to next space (or end of buffer) */
+    /* count bytes up to next space (or end of buffer) */
     q = p;
     while ( !( *q == ' ' || *q == '\0' ) )
       GET_UTF8_CHAR( dummy, q );
@@ -483,6 +483,46 @@
     /* glyph indices, possibly applying a feature                   */
     hb_shape( font, buf, feature, feature ? 1 : 0 );
 
+    if ( feature )
+    {
+      hb_buffer_t*  hb_buf = metrics->globals->hb_buf;
+
+      unsigned int      gcount;
+      hb_glyph_info_t*  ginfo;
+
+      unsigned int      hb_gcount;
+      hb_glyph_info_t*  hb_ginfo;
+
+
+      /* we have to check whether applying a feature does actually change */
+      /* glyph indices; otherwise the affected glyph or glyphs aren't     */
+      /* available at all in the feature                                  */
+
+      hb_buffer_clear_contents( hb_buf );
+      hb_buffer_add_utf8( hb_buf, p, len, 0, len );
+      hb_buffer_guess_segment_properties( hb_buf );
+      hb_shape( font, hb_buf, NULL, 0 );
+
+      ginfo    = hb_buffer_get_glyph_infos( buf, &gcount );
+      hb_ginfo = hb_buffer_get_glyph_infos( hb_buf, &hb_gcount );
+
+      if ( gcount == hb_gcount )
+      {
+        unsigned int  i;
+
+
+        for (i = 0; i < gcount; i++ )
+          if ( ginfo[i].codepoint != hb_ginfo[i].codepoint )
+            break;
+
+        if ( i == gcount )
+        {
+          /* both buffers have identical glyph indices */
+          hb_buffer_clear_contents( buf );
+        }
+      }
+    }
+
     *count = hb_buffer_get_length( buf );
 
 #ifdef FT_DEBUG_LEVEL_TRACE