[dwrite] Provide an experimental API for justification (#279)

src/hb-directwrite.cc

@@ -542,12 +542,13 @@ static inline uint32_t hb_uint32_swap (const uint32_t v)
  * shaper
  */
 
-hb_bool_t
-_hb_directwrite_shape(hb_shape_plan_t    *shape_plan,
+static hb_bool_t
+_hb_directwrite_shape_full(hb_shape_plan_t    *shape_plan,
   hb_font_t          *font,
   hb_buffer_t        *buffer,
   const hb_feature_t *features,
-  unsigned int        num_features)
+  unsigned int        num_features,
+  float               lineWidth)
 {
   hb_face_t *face = font->face;
   hb_directwrite_shaper_face_data_t *face_data = HB_SHAPER_DATA_GET (face);
@@ -728,9 +729,6 @@ retry_getglyphs:
     return false;
   }
 
-  // TODO: get lineWith from somewhere
-  float lineWidth = 0;
-
   IDWriteTextAnalyzer1* analyzer1;
   analyzer->QueryInterface (&analyzer1);
 
@@ -900,3 +898,37 @@ retry_getglyphs:
   /* Wow, done! */
   return true;
 }
+
+hb_bool_t
+_hb_directwrite_shape(hb_shape_plan_t    *shape_plan,
+  hb_font_t          *font,
+  hb_buffer_t        *buffer,
+  const hb_feature_t *features,
+  unsigned int        num_features)
+{
+  return _hb_directwrite_shape_full(shape_plan, font, buffer,
+    features, num_features, 0);
+}
+
+/*
+ * Public [experimental] API
+ */
+
+hb_bool_t
+hb_shape_dwrite_experimental_width(hb_font_t          *font,
+  hb_buffer_t        *buffer,
+  const hb_feature_t *features,
+  unsigned int        num_features,
+  float               width)
+{
+  static char *shapers = "directwrite";
+  hb_shape_plan_t *shape_plan = hb_shape_plan_create_cached (font->face,
+    &buffer->props, features, num_features, &shapers);
+  hb_bool_t res = _hb_directwrite_shape_full (shape_plan, font, buffer,
+    features, num_features, width);
+
+  if (res)
+    buffer->content_type = HB_BUFFER_CONTENT_TYPE_GLYPHS;
+
+  return res;
+}

src/hb-directwrite.h

@@ -29,6 +29,10 @@
 
 HB_BEGIN_DECLS
 
+HB_EXTERN hb_bool_t
+hb_shape_dwrite_experimental_width(hb_font_t *font, hb_buffer_t *buffer,
+  const hb_feature_t *features, unsigned int num_features, float width);
+
 HB_END_DECLS
 
 #endif /* HB_DIRECTWRITE_H */