Implement opbd table parsing

https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6opbd.html

src/Makefile.sources

@@ -10,6 +10,7 @@ HB_BASE_sources = \
 	hb-aat-layout-kerx-table.hh \
 	hb-aat-layout-lcar-table.hh \
 	hb-aat-layout-morx-table.hh \
+	hb-aat-layout-opbd-table.hh \
 	hb-aat-layout-trak-table.hh \
 	hb-aat-layout.cc \
 	hb-aat-layout.hh \

src/hb-aat-layout-opbd-table.hh

@@ -0,0 +1,111 @@
+/*
+ * Copyright © 2019  Ebrahim Byagowi
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#ifndef HB_AAT_LAYOUT_OPBD_TABLE_HH
+#define HB_AAT_LAYOUT_OPBD_TABLE_HH
+
+#include "hb-aat-layout-common.hh"
+#include "hb-open-type.hh"
+
+/*
+ * opbd -- Optical Bounds
+ * https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6opbd.html
+ */
+#define HB_AAT_TAG_opbd HB_TAG('o','p','b','d')
+
+
+namespace AAT {
+
+struct OpticalBounds
+{
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this)));
+  }
+
+  HBINT16	leftSide;
+  HBINT16	topSide;
+  HBINT16	rightSide;
+  HBINT16	bottomSide;
+  public:
+  DEFINE_SIZE_STATIC (8);
+};
+
+struct opbd
+{
+  static constexpr hb_tag_t tableTag = HB_AAT_TAG_opbd;
+
+  bool get_optical_bounds (hb_font_t *font, hb_codepoint_t glyph_id,
+			   hb_position_t *left, hb_position_t *top,
+			   hb_position_t *right, hb_position_t *bottom) const
+  {
+    const OffsetTo<OpticalBounds> *bounds_offset = lookupTable.get_value (glyph_id, font->face->get_num_glyphs ());
+    if (!bounds_offset) return false;
+    const OpticalBounds &bounds = this+*bounds_offset;
+    switch (format)
+    {
+    case 0:
+      *left = font->em_scale_x (bounds.leftSide);
+      *top = font->em_scale_y (bounds.topSide);
+      *right = font->em_scale_x (bounds.rightSide);
+      *bottom = font->em_scale_y (bounds.bottomSide);
+      return true;
+    case 1:
+      hb_position_t ignore;
+      return font->get_glyph_contour_point (glyph_id, bounds.leftSide, left, &ignore) &&
+	     font->get_glyph_contour_point (glyph_id, bounds.topSide, &ignore, top) &&
+	     font->get_glyph_contour_point (glyph_id, bounds.rightSide, right, &ignore) &&
+	     font->get_glyph_contour_point (glyph_id, bounds.bottomSide, &ignore, bottom);
+    default:
+      return false;
+    }
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this) &&
+			  version.major == 1 &&
+			  lookupTable.sanitize (c, this)));
+  }
+
+  protected:
+  FixedVersion<>version;	/* Version number of the optical bounds
+				 * table (0x00010000 for the current version). */
+  HBUINT16	format;		/* Format of the optical bounds table.
+				 * Format 0 indicates distance and Format 1 indicates
+				 * control point. */
+  Lookup<OffsetTo<OpticalBounds>>
+		lookupTable;	/* Lookup table associating glyphs with the four
+				 * int16 values for the left-side, top-side,
+				 * right-side, and bottom-side optical bounds. */
+  public:
+  DEFINE_SIZE_MIN (8);
+};
+
+} /* namespace AAT */
+
+
+#endif /* HB_AAT_LAYOUT_OPBD_TABLE_HH */

src/hb-ot-face-table-list.hh

@@ -115,6 +115,7 @@ HB_OT_TABLE (AAT, trak)
 HB_OT_TABLE (AAT, lcar)
 HB_OT_TABLE (AAT, ltag)
 HB_OT_TABLE (AAT, feat)
+// HB_OT_TABLE (AAT, opbd)
 #endif
 
 /* OpenType color fonts. */

src/hb-ot-layout.cc

@@ -54,6 +54,7 @@
 #include "hb-aat-layout-lcar-table.hh"
 #include "hb-aat-layout-morx-table.hh"
 
+#include "hb-aat-layout-opbd-table.hh" // Just so we compile it; unused otherwise.
 
 /**
  * SECTION:hb-ot-layout