Make `FT_Get_Color_Glyph_Layer' return FT_Bool.

* include/freetype/freetype.h, src/base/ftobjs.c
(FT_Get_Color_Glyph_Layer, FT_Render_Glyph_Internal): Updated.

* include/freetype/internal/sfnt.h (TT_Get_Colr_Layer_Func),
src/sfnt/ttcolr.h, src/sfnt/ttcolr.c (tt_face_get_colr_layer):
Updated.

6 files changed, 71 insertions, 42 deletions

diff --git a/ChangeLog b/ChangeLog
index dd5738811..2b6c0588a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2018-07-02  Werner Lemberg  <wl@gnu.org>
+
+	Make `FT_Get_Color_Glyph_Layer' return FT_Bool.
+
+	* include/freetype/freetype.h, src/base/ftobjs.c
+	(FT_Get_Color_Glyph_Layer, FT_Render_Glyph_Internal): Updated.
+
+	* include/freetype/internal/sfnt.h (TT_Get_Colr_Layer_Func),
+	src/sfnt/ttcolr.h, src/sfnt/ttcolr.c (tt_face_get_colr_layer):
+	Updated.
+
 2018-07-01  Werner Lemberg  <wl@gnu.org>
 
 	* src/base/ftobjs.c (FT_Get_Color_Glyph_Layer): Guard SFNT function.
diff --git a/include/freetype/freetype.h b/include/freetype/freetype.h
index a5896e973..2f58d25b3 100644
--- a/include/freetype/freetype.h
+++ b/include/freetype/freetype.h
@@ -4255,6 +4255,9 @@ FT_BEGIN_HEADER
    *     same object again.
    *
    * @output:
+   *   aglyph_index ::
+   *     The glyph index of the current layer.
+   *
    *   acolor_index ::
    *     The color index into the font face's color palette of the current
    *     layer.  The value 0xFFFF is special; it doesn't reference a palette
@@ -4264,9 +4267,9 @@ FT_BEGIN_HEADER
    *     The color palette can be retrieved with @FT_Palette_Select.
    *
    * @return:
-   *     The glyph index of the current layer.  If there are no more layers
-   *     (or if there are no layers at all), value~0 gets returned.  In case
-   *     of an error, value~0 is returned also.
+   *   Value~1 if everything is OK.  If there are no more layers (or if
+   *   there are no layers at all), value~0 gets returned.  In case of an
+   *   error, value~0 is returned also.
    *
    * @note:
    *   This function is necessary if you want to handle glyph layers by
@@ -4282,6 +4285,7 @@ FT_BEGIN_HEADER
    *     FT_Color*         palette;
    *     FT_LayerIterator  iterator;
    *
+   *     FT_Bool  have_layers;
    *     FT_UInt  layer_glyph_index;
    *     FT_UInt  layer_color_index;
    *
@@ -4290,33 +4294,41 @@ FT_BEGIN_HEADER
    *     if ( error )
    *       palette = NULL;
    *
-   *     iterator.p        = NULL;
-   *     layer_glyph_index = FT_Get_Color_Glyph_Layer( face,
-   *                                                   glyph_index,
-   *                                                   &layer_color_index,
-   *                                                   &iterator );
+   *     iterator.p  = NULL;
+   *     have_layers = FT_Get_Color_Glyph_Layer( face,
+   *                                             glyph_index,
+   *                                             &layer_glyph_index,
+   *                                             &layer_color_index,
+   *                                             &iterator );
    *
-   *     if ( palette && layer_glyph_index )
+   *     if ( palette && have_layers )
    *     {
    *       do
    *       {
-   *         FT_Color  layer_color = palette[layer_color_index];
+   *         FT_Color  layer_color;
    *
    *
-   *         // Load and render glyph `layer_glyph_index', then
-   *         // blend resulting pixmap with previously created pixmaps.
+   *         if ( layer_color_index == 0xFFFF )
+   *           layer_color = text_foreground_color;
+   *         else
+   *           layer_color = palette[layer_color_index];
    *
-   *       } while ( ( layer_glyph_index =
-   *                     FT_Get_Color_Glyph_Layer( face,
-   *                                               glyph_index,
-   *                                               &layer_color_index,
-   *                                               &iterator ) ) != 0 );
+   *         // Load and render glyph `layer_glyph_index', then
+   *         // blend resulting pixmap (using color `layer_color')
+   *         // with previously created pixmaps.
+   *
+   *       } while ( FT_Get_Color_Glyph_Layer( face,
+   *                                           glyph_index,
+   *                                           &layer_glyph_index,
+   *                                           &layer_color_index,
+   *                                           &iterator ) );
    *     }
    *   }
    */
-  FT_EXPORT( FT_UInt )
+  FT_EXPORT( FT_Bool )
   FT_Get_Color_Glyph_Layer( FT_Face            face,
                             FT_UInt            base_glyph,
+                            FT_UInt           *aglyph_index,
                             FT_UInt           *acolor_index,
                             FT_LayerIterator*  iterator );
 
diff --git a/include/freetype/internal/sfnt.h b/include/freetype/internal/sfnt.h
index deb1ed4a2..5588f5ddf 100644
--- a/include/freetype/internal/sfnt.h
+++ b/include/freetype/internal/sfnt.h
@@ -514,6 +514,9 @@ FT_BEGIN_HEADER
    *     same object again.
    *
    * @output:
+   *   aglyph_index ::
+   *     The glyph index of the current layer.
+   *
    *   acolor_index ::
    *     The color index into the font face's color palette of the current
    *     layer.  The value 0xFFFF is special; it doesn't reference a palette
@@ -521,13 +524,14 @@ FT_BEGIN_HEADER
    *     instead (to be set up by the application outside of FreeType).
    *
    * @return:
-   *   The glyph index of the current layer.  If there are no more layers
-   *   (or if there are no layers at all), value~0 gets returned.  In case
-   *   of an error, value~0 is returned also.
+   *   Value~1 if everything is OK.  If there are no more layers (or if
+   *   there are no layers at all), value~0 gets returned.  In case of an
+   *   error, value~0 is returned also.
    */
-  typedef FT_UInt
+  typedef FT_Bool
   (*TT_Get_Colr_Layer_Func)( TT_Face            face,
                              FT_UInt            base_glyph,
+                             FT_UInt           *aglyph_index,
                              FT_UInt           *acolor_index,
                              FT_LayerIterator*  iterator );
 
diff --git a/src/base/ftobjs.c b/src/base/ftobjs.c
index fa58768e6..4f237e23e 100644
--- a/src/base/ftobjs.c
+++ b/src/base/ftobjs.c
@@ -4517,17 +4517,19 @@
 
         FT_UInt  base_glyph = slot->glyph_index;
 
+        FT_Bool  have_layers;
         FT_UInt  glyph_index;
         FT_UInt  color_index;
 
 
         /* check whether we have colored glyph layers */
         iterator.p  = NULL;
-        glyph_index = FT_Get_Color_Glyph_Layer( face,
+        have_layers = FT_Get_Color_Glyph_Layer( face,
                                                 base_glyph,
+                                                &glyph_index,
                                                 &color_index,
                                                 &iterator );
-        if ( glyph_index )
+        if ( have_layers )
         {
           error = FT_New_GlyphSlot( face, NULL );
           if ( !error )
@@ -4546,7 +4548,7 @@
               load_flags &= ~FT_LOAD_COLOR;
 
               /* render into the new `face->glyph' glyph slot */
-              load_flags |=  FT_LOAD_RENDER;
+              load_flags |= FT_LOAD_RENDER;
 
               error = FT_Load_Glyph( face, glyph_index, load_flags );
               if ( error )
@@ -4561,11 +4563,11 @@
               if ( error )
                 break;
 
-            } while ( ( glyph_index =
-                          FT_Get_Color_Glyph_Layer( face,
-                                                    base_glyph,
-                                                    &color_index,
-                                                    &iterator ) ) != 0 );
+            } while ( FT_Get_Color_Glyph_Layer( face,
+                                                base_glyph,
+                                                &glyph_index,
+                                                &color_index,
+                                                &iterator ) );
 
             if ( !error )
               slot->format = FT_GLYPH_FORMAT_BITMAP;
@@ -5471,9 +5473,10 @@
 
   /* documentation is in freetype.h */
 
-  FT_EXPORT_DEF( FT_UInt )
+  FT_EXPORT_DEF( FT_Bool )
   FT_Get_Color_Glyph_Layer( FT_Face            face,
                             FT_UInt            base_glyph,
+                            FT_UInt           *aglyph_index,
                             FT_UInt           *acolor_index,
                             FT_LayerIterator*  iterator )
   {
@@ -5482,6 +5485,7 @@
 
 
     if ( !face                                   ||
+         !aglyph_index                           ||
          !acolor_index                           ||
          !iterator                               ||
          base_glyph >= (FT_UInt)face->num_glyphs )
@@ -5496,14 +5500,11 @@
     if ( sfnt->get_colr_layer )
       return sfnt->get_colr_layer( ttface,
                                    base_glyph,
+                                   aglyph_index,
                                    acolor_index,
                                    iterator );
     else
-    {
-      *acolor_index = 0;
-
       return 0;
-    }
   }
 
 
diff --git a/src/sfnt/ttcolr.c b/src/sfnt/ttcolr.c
index 4dab9724b..9151ab5fa 100644
--- a/src/sfnt/ttcolr.c
+++ b/src/sfnt/ttcolr.c
@@ -209,15 +209,15 @@
   }
 
 
-  FT_LOCAL_DEF( FT_UInt )
+  FT_LOCAL_DEF( FT_Bool )
   tt_face_get_colr_layer( TT_Face            face,
                           FT_UInt            base_glyph,
+                          FT_UInt           *aglyph_index,
                           FT_UInt           *acolor_index,
                           FT_LayerIterator*  iterator )
   {
-    Colr*            colr   = (Colr*)face->colr;
+    Colr*            colr = (Colr*)face->colr;
     BaseGlyphRecord  glyph_record;
-    FT_UInt          glyph_index;
 
 
     if ( !colr )
@@ -252,17 +252,17 @@
     if ( iterator->layer >= iterator->num_layers )
       return 0;
 
-    glyph_index   = FT_NEXT_USHORT( iterator->p );
+    *aglyph_index = FT_NEXT_USHORT( iterator->p );
     *acolor_index = FT_NEXT_USHORT( iterator->p );
 
-    if ( glyph_index >= FT_FACE( face )->num_glyphs                  ||
+    if ( *aglyph_index >= FT_FACE( face )->num_glyphs                ||
          ( *acolor_index != 0xFFFF                                 &&
            *acolor_index >= face->palette_data.num_palette_entries ) )
       return 0;
 
     iterator->layer++;
 
-    return glyph_index;
+    return 1;
   }
 
 
diff --git a/src/sfnt/ttcolr.h b/src/sfnt/ttcolr.h
index 983ab831e..46cc0813e 100644
--- a/src/sfnt/ttcolr.h
+++ b/src/sfnt/ttcolr.h
@@ -36,9 +36,10 @@ FT_BEGIN_HEADER
   FT_LOCAL( void )
   tt_face_free_colr( TT_Face  face );
 
-  FT_LOCAL( FT_UInt )
+  FT_LOCAL( FT_Bool )
   tt_face_get_colr_layer( TT_Face            face,
                           FT_UInt            base_glyph,
+                          FT_UInt           *aglyph_index,
                           FT_UInt           *acolor_index,
                           FT_LayerIterator*  iterator );