[ot-font] Implement TrueType v_origin

Fixes https://github.com/harfbuzz/harfbuzz/issues/537

src/hb-ot-font.cc

@@ -126,6 +126,35 @@ hb_ot_get_glyph_v_advances (hb_font_t* font, void* font_data,
   }
 }
 
+static hb_bool_t
+hb_ot_get_glyph_v_origin (hb_font_t *font,
+			  void *font_data,
+			  hb_codepoint_t glyph,
+			  hb_position_t *x,
+			  hb_position_t *y,
+			  void *user_data HB_UNUSED)
+{
+  const hb_ot_face_data_t *ot_face = (const hb_ot_face_data_t *) font_data;
+
+  *x = font->get_glyph_h_advance (glyph) / 2;
+
+  hb_glyph_extents_t extents = {0};
+  bool ret = ot_face->glyf->get_extents (glyph, &extents);
+  if (ret)
+  {
+    const OT::vmtx_accelerator_t &vmtx = *ot_face->vmtx.get ();
+    hb_position_t tsb = vmtx.get_side_bearing (glyph);
+    *y = font->em_scale_y (extents.y_bearing + tsb);
+    return true;
+  }
+
+  hb_font_extents_t font_extents;
+  font->get_h_extents_with_fallback (&font_extents);
+  *y = font_extents.ascender;
+
+  return true;
+}
+
 static hb_bool_t
 hb_ot_get_glyph_extents (hb_font_t *font,
 			 void *font_data,
@@ -215,7 +244,7 @@ static struct hb_ot_font_funcs_lazy_loader_t : hb_font_funcs_lazy_loader_t<hb_ot
     hb_font_funcs_set_glyph_h_advances_func (funcs, hb_ot_get_glyph_h_advances, nullptr, nullptr);
     hb_font_funcs_set_glyph_v_advances_func (funcs, hb_ot_get_glyph_v_advances, nullptr, nullptr);
     //hb_font_funcs_set_glyph_h_origin_func (funcs, hb_ot_get_glyph_h_origin, nullptr, nullptr);
-    //hb_font_funcs_set_glyph_v_origin_func (funcs, hb_ot_get_glyph_v_origin, nullptr, nullptr);
+    hb_font_funcs_set_glyph_v_origin_func (funcs, hb_ot_get_glyph_v_origin, nullptr, nullptr);
     hb_font_funcs_set_glyph_extents_func (funcs, hb_ot_get_glyph_extents, nullptr, nullptr);
     //hb_font_funcs_set_glyph_contour_point_func (funcs, hb_ot_get_glyph_contour_point, nullptr, nullptr);
     hb_font_funcs_set_glyph_name_func (funcs, hb_ot_get_glyph_name, nullptr, nullptr);

src/hb-ot-hmtx-table.hh

@@ -48,7 +48,7 @@ namespace OT {
 struct LongMetric
 {
   UFWORD	advance; /* Advance width/height. */
-  FWORD		lsb; /* Leading (left/top) side bearing. */
+  FWORD		sb; /* Leading (left/top) side bearing. */
   public:
   DEFINE_SIZE_STATIC (4);
 };
@@ -134,8 +134,8 @@ struct hmtxvmtx
         }
         else
         {
-          /* dest just lsb */
+          /* dest just sb */
-          *((FWORD *) dest_pos) = src_metric->lsb;
+          *((FWORD *) dest_pos) = src_metric->sb;
         }
       }
       else
@@ -147,18 +147,18 @@ struct hmtxvmtx
 	  failed = true;
 	  break;
 	}
-	FWORD src_lsb = *(lsbs + gids[i] - _mtx.num_advances);
+	FWORD src_sb = *(lsbs + gids[i] - _mtx.num_advances);
         if (i < num_advances)
         {
           /* dest needs a full LongMetric */
           LongMetric *metric = (LongMetric *)dest_pos;
           metric->advance = src_metric->advance;
-          metric->lsb = src_lsb;
+          metric->sb = src_sb;
         }
         else
         {
-          /* dest just needs an lsb */
+          /* dest just needs an sb */
-          *((FWORD *) dest_pos) = src_lsb;
+          *((FWORD *) dest_pos) = src_sb;
         }
       }
       dest_pos += (i < num_advances ? 4 : 2);
@@ -249,17 +249,30 @@ struct hmtxvmtx
       hb_blob_destroy (var_blob);
     }
 
+    /* TODO Add variations version. */
+    inline unsigned int get_side_bearing (hb_codepoint_t glyph) const
+    {
+      if (glyph < num_advances)
+        return table->longMetricZ[glyph].sb;
+
+      if (unlikely (glyph > num_metrics))
+        return 0;
+
+      const FWORD *bearings = (const FWORD *) &table->longMetricZ[num_advances];
+      return bearings[glyph - num_advances];
+    }
+
     inline unsigned int get_advance (hb_codepoint_t glyph) const
     {
       if (unlikely (glyph >= num_metrics))
       {
-        /* If num_metrics is zero, it means we don't have the metrics table
+	/* If num_metrics is zero, it means we don't have the metrics table
-         * for this direction: return default advance.  Otherwise, it means that the
+	 * for this direction: return default advance.  Otherwise, it means that the
-         * glyph index is out of bound: return zero. */
+	 * glyph index is out of bound: return zero. */
-        if (num_metrics)
+	if (num_metrics)
-          return 0;
+	  return 0;
-        else
+	else
-          return default_advance;
+	  return default_advance;
       }
 
       return table->longMetricZ[MIN (glyph, (uint32_t) num_advances - 1)].advance;
@@ -271,7 +284,7 @@ struct hmtxvmtx
       unsigned int advance = get_advance (glyph);
       if (likely(glyph < num_metrics))
       {
-        advance += (font->num_coords ? var_table->get_advance_var (glyph, font->coords, font->num_coords) : 0); // TODO Optimize?!
+	advance += (font->num_coords ? var_table->get_advance_var (glyph, font->coords, font->num_coords) : 0); // TODO Optimize?!
       }
       return advance;
     }

test/shaping/data/in-house/tests/vertical.tests

@@ -1,3 +1,3 @@
 ../fonts/191826b9643e3f124d865d617ae609db6a2ce203.ttf:--direction=t --font-funcs=ft:U+300C:[uni300C.vert=0@-512,-578+0,-1024]
 ../fonts/f9b1dd4dcb515e757789a22cb4241107746fd3d0.ttf:--direction=t --font-funcs=ft:U+0041,U+0042:[gid1=0@-654,-2128+0,-2789|gid2=1@-665,-2125+0,-2789]
-../fonts/f9b1dd4dcb515e757789a22cb4241107746fd3d0.ttf:--direction=t --font-funcs=ot:U+0041,U+0042:[gid1=0@-654,-2189+0,-2048|gid2=1@-665,-2189+0,-2048]
+../fonts/f9b1dd4dcb515e757789a22cb4241107746fd3d0.ttf:--direction=t --font-funcs=ot:U+0041,U+0042:[gid1=0@-654,-1468+0,-2048|gid2=1@-665,-1462+0,-2048]