[just] Initial table implementation (#1364)

A starting point, its sanitization is not tested however

src/Makefile.sources

@@ -100,6 +100,7 @@ HB_OT_sources = \
 	hb-aat-layout-ankr-table.hh \
 	hb-aat-layout-bsln-table.hh \
 	hb-aat-layout-feat-table.hh \
+	hb-aat-layout-just-table.hh \
 	hb-aat-layout-kerx-table.hh \
 	hb-aat-layout-morx-table.hh \
 	hb-aat-layout-trak-table.hh \

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

+/*
+ * Copyright © 2018  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_JUST_TABLE_HH
+#define HB_AAT_LAYOUT_JUST_TABLE_HH
+
+#include "hb-aat-layout-common.hh"
+#include "hb-ot-layout.hh"
+#include "hb-open-type.hh"
+
+#include "hb-aat-layout-morx-table.hh"
+
+/*
+ * just -- Justification
+ * https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6just.html
+ */
+#define HB_AAT_TAG_just HB_TAG('j','u','s','t')
+
+
+namespace AAT {
+
+using namespace OT;
+
+
+struct ActionSubrecordHeader
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this)));
+  }
+
+  HBUINT16 	actionClass; 	/* The JustClass value associated with this
+				 * ActionSubrecord. */
+  HBUINT16 	actionType; 	/* The type of postcompensation action. */
+  HBUINT16 	actionLength;	/* Length of this ActionSubrecord record, which
+				 * must be a multiple of 4. */
+  public:
+  DEFINE_SIZE_STATIC (6);
+};
+
+struct DecompositionAction
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this)));
+  }
+
+  ActionSubrecordHeader
+		header;
+  Fixed		lowerLimit; 	/* If the distance factor is less than this value,
+				 * then the ligature is decomposed. */
+  Fixed		upperLimit; 	/* If the distance factor is greater than this value,
+				 * then the ligature is decomposed. */
+  HBUINT16 	order;		/* Numerical order in which this ligature will
+				 * be decomposed; you may want infrequent ligatures
+				 * to decompose before more frequent ones. The ligatures
+				 * on the line of text will decompose in increasing
+				 * value of this field. */
+  ArrayOf<HBUINT16>
+		decomposedglyphs;
+				/* Number of 16-bit glyph indexes that follow;
+				 * the ligature will be decomposed into these glyphs.
+				 *
+				 * Array of decomposed glyphs. */
+  public:
+  DEFINE_SIZE_ARRAY (18, decomposedglyphs);
+};
+
+struct UnconditionalAddGlyphAction
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this));
+  }
+
+  protected:
+  ActionSubrecordHeader
+		header;
+  GlyphID	addGlyph;	/* Glyph that should be added if the distance factor
+				 * is growing. */
+
+  public:
+  DEFINE_SIZE_STATIC (8);
+};
+
+struct ConditionalAddGlyphAction
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this)));
+  }
+
+  protected:
+  ActionSubrecordHeader
+		header;
+  Fixed 	substThreshold; /* Distance growth factor (in ems) at which
+				 * this glyph is replaced and the growth factor
+				 * recalculated. */
+  GlyphID 	addGlyph; 	/* Glyph to be added as kashida. If this value is
+				 * 0xFFFF, no extra glyph will be added. Note that
+				 * generally when a glyph is added, justification
+				 * will need to be redone. */
+  GlyphID 	substGlyph; 	/* Glyph to be substituted for this glyph if the
+				 * growth factor equals or exceeds the value of
+				 * substThreshold. */
+  public:
+  DEFINE_SIZE_STATIC (14);
+};
+
+struct DuctileGlyphAction
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this)));
+  }
+
+  protected:
+  ActionSubrecordHeader
+		header;
+  HBUINT32 	variationAxis;	/* The 4-byte tag identifying the ductile axis.
+				 * This would normally be 0x64756374 ('duct'),
+				 * but you may use any axis the font contains. */
+  Fixed 	minimumLimit; 	/* The lowest value for the ductility axis tha
+				 * still yields an acceptable appearance. Normally
+				 * this will be 1.0. */
+  Fixed 	noStretchValue; /* This is the default value that corresponds to
+				 * no change in appearance. Normally, this will
+				 * be 1.0. */
+  Fixed 	maximumLimit; 	/* The highest value for the ductility axis that
+				 * still yields an acceptable appearance. */
+  public:
+  DEFINE_SIZE_STATIC (22);
+};
+
+struct RepeatedAddGlyphAction
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this)));
+  }
+
+  protected:
+  ActionSubrecordHeader
+		header;
+  HBUINT16 	flags;		/* Currently unused; set to 0. */
+  GlyphID 	glyph;		/* Glyph that should be added if the distance factor
+				 * is growing. */
+  public:
+  DEFINE_SIZE_STATIC (10);
+};
+
+struct ActionSubrecord
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    if (unlikely (!c->check_struct (this)))
+      return_trace (false);
+
+    switch (u.header.actionType)
+    {
+    case 0:  return_trace (u.decompositionAction.sanitize (c));
+    case 1:  return_trace (u.unconditionalAddGlyphAction.sanitize (c));
+    case 2:  return_trace (u.conditionalAddGlyphAction.sanitize (c));
+    // case 3: return_trace (u.stretchGlyphAction.sanitize (c));
+    case 4:  return_trace (u.decompositionAction.sanitize (c));
+    case 5:  return_trace (u.decompositionAction.sanitize (c));
+    default: return_trace (true);
+    }
+  }
+
+  inline unsigned int get_length () const { return u.header.actionLength; }
+
+  protected:
+  union	{
+  ActionSubrecordHeader		header;
+  DecompositionAction		decompositionAction;
+  UnconditionalAddGlyphAction	unconditionalAddGlyphAction;
+  ConditionalAddGlyphAction	conditionalAddGlyphAction;
+  /* StretchGlyphAction stretchGlyphAction; -- Not supported by CoreText */
+  DuctileGlyphAction		ductileGlyphAction;
+  RepeatedAddGlyphAction	repeatedAddGlyphAction;
+  } u;				/* Data. The format of this data depends on
+				 * the value of the actionType field. */
+  public:
+  DEFINE_SIZE_UNION (6, header);
+};
+
+struct PostcompensationActionChain
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    if (unlikely (!c->check_struct (this)))
+      return_trace (false);
+
+    unsigned int offset = min_size;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      const ActionSubrecord& subrecord = StructAtOffset<ActionSubrecord> (this, offset);
+      if (unlikely (!subrecord.sanitize (c))) return_trace (false);
+      offset += subrecord.get_length ();
+    }
+
+    return_trace (true);
+  }
+
+  protected:
+  HBUINT32	count;
+
+  public:
+  DEFINE_SIZE_STATIC (4);
+};
+
+struct JustWidthDeltaEntry
+{
+  enum Flags
+  {
+    Reserved1		=0xE000,/* Reserved. You should set these bits to zero. */
+    UnlimiteGap		=0x1000,/* The glyph can take unlimited gap. When this
+				 * glyph participates in the justification process,
+				 * it and any other glyphs on the line having this
+				 * bit set absorb all the remaining gap. */
+    Reserved2		=0x0FF0,/* Reserved. You should set these bits to zero. */
+    Priority		=0x000F /* The justification priority of the glyph. */
+  };
+
+  enum Priority
+  {
+    Kashida		= 0,	/* Kashida priority. This is the highest priority
+				 * during justification. */
+    Whitespace		= 1,	/* Whitespace priority. Any whitespace glyphs (as
+				 * identified in the glyph properties table) will
+				 * get this priority. */
+    InterCharacter	= 2,	/* Inter-character priority. Give this to any
+				 * remaining glyphs. */
+    NullPriority	= 3	/* Null priority. You should set this priority for
+				 * glyphs that only participate in justification
+				 * after the above priorities. Normally all glyphs
+				 * have one of the previous three values. If you
+				 * don't want a glyph to participate in justification,
+				 * and you don't want to set its factors to zero,
+				 * you may instead assign it to the null priority. */
+  };
+
+  protected:
+  Fixed		beforeGrowLimit;/* The ratio by which the advance width of the
+				 * glyph is permitted to grow on the left or top side. */
+  Fixed		beforeShrinkLimit;
+				/* The ratio by which the advance width of the
+				 * glyph is permitted to shrink on the left or top side. */
+  Fixed		afterGrowLimit;	/* The ratio by which the advance width of the glyph
+				 * is permitted to shrink on the left or top side. */
+  Fixed		afterShrinkLimit;
+				/* The ratio by which the advance width of the glyph
+				 * is at most permitted to shrink on the right or
+				 * bottom side. */
+  HBUINT16	growFlags;	/* Flags controlling the grow case. */
+  HBUINT16	shrinkFlags;	/* Flags controlling the shrink case. */
+
+  public:
+  DEFINE_SIZE_STATIC (20);
+};
+
+struct WidthDeltaPair
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this)));
+  }
+
+  protected:
+  HBUINT32	justClass;	/* The justification category associated
+				 * with the wdRecord field. Only 7 bits of
+				 * this field are used. (The other bits are
+				 * used as padding to guarantee longword
+				 * alignment of the following record). */
+  JustWidthDeltaEntry
+		wdRecord;	/* The actual width delta record. */
+
+  public:
+  DEFINE_SIZE_STATIC (24);
+};
+
+struct WidthDeltaCluster : OT::LArrayOf<WidthDeltaPair> {};
+
+struct JustificationCategory
+{
+  typedef void EntryData;
+
+  enum Flags
+  {
+    SetMark		=0x8000,/* If set, make the current glyph the marked
+				 * glyph. */
+    DontAdvance		=0x4000,/* If set, don't advance to the next glyph before
+				 * going to the new state. */
+    MarkCategory	=0x3F80,/* The justification category for the marked
+				 * glyph if nonzero. */
+    CurrentCategory	=0x007F /* The justification category for the current
+				 * glyph if nonzero. */
+  };
+
+  inline bool sanitize (hb_sanitize_context_t *c, const void *base) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this) &&
+			  morphHeader.sanitize (c) &&
+			  stHeader.sanitize (c)));
+  }
+
+  protected:
+  ChainSubtable<ObsoleteTypes>
+		morphHeader;	/* Metamorphosis-style subtable header. */
+  StateTable<ObsoleteTypes, EntryData>
+		stHeader;	/* The justification insertion state table header */
+  public:
+  DEFINE_SIZE_STATIC (30);
+};
+
+struct JustificationHeader
+{
+  inline bool sanitize (hb_sanitize_context_t *c, const void *base) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this) &&
+			  justClassTable.sanitize (c, base, base) &&
+			  wdcTable.sanitize (c, base) &&
+			  pcTable.sanitize (c, base) &&
+			  lookupTable.sanitize (c, base)));
+  }
+
+  protected:
+  OffsetTo<JustificationCategory>
+		justClassTable;	/* Offset to the justification category state table. */
+  OffsetTo<WidthDeltaCluster>
+  		wdcTable;	/* Offset from start of justification table to start
+				 * of the subtable containing the width delta factors
+				 * for the glyphs in your font.
+				 *
+				 * The width delta clusters table. */
+  OffsetTo<PostcompensationActionChain>
+		pcTable;	/* Offset from start of justification table to start
+				 * of postcompensation subtable (set to zero if none).
+				 *
+				 * The postcompensation subtable, if present in the font. */
+  Lookup<OffsetTo<WidthDeltaCluster> >
+  		lookupTable;	/* Lookup table associating glyphs with width delta
+				 * clusters. See the description of Width Delta Clusters
+				 * table for details on how to interpret the lookup values. */
+
+  public:
+  DEFINE_SIZE_MIN (8);
+};
+
+struct just
+{
+  static const hb_tag_t tableTag = HB_AAT_TAG_just;
+
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+
+    return_trace (unlikely (c->check_struct (this) &&
+			    horizData.sanitize (c, this, this) &&
+			    vertData.sanitize (c, this, this)));
+  }
+
+  protected:
+  FixedVersion<>version;	/* Version of the justification table
+				 * (0x00010000u for version 1.0). */
+  HBUINT16	format; 	/* Format of the justification table (set to 0). */
+  OffsetTo<JustificationHeader>
+		horizData;	/* Byte offset from the start of the justification table
+				 * to the header for tables that contain justification
+				 * information for horizontal text.
+				 * If you are not including this information,
+				 * store 0. */
+  OffsetTo<JustificationHeader>
+		vertData;	/* ditto, vertical */
+
+  public:
+  DEFINE_SIZE_STATIC (10);
+};
+
+} /* namespace AAT */
+
+
+#endif /* HB_AAT_LAYOUT_JUST_TABLE_HH */

src/hb-aat-layout.cc

@@ -31,6 +31,7 @@
 #include "hb-aat-layout-ankr-table.hh"
 #include "hb-aat-layout-bsln-table.hh" // Just so we compile it; unused otherwise.
 #include "hb-aat-layout-feat-table.hh" // Just so we compile it; unused otherwise.
+#include "hb-aat-layout-just-table.hh" // Just so we compile it; unused otherwise.
 #include "hb-aat-layout-kerx-table.hh"
 #include "hb-aat-layout-morx-table.hh"
 #include "hb-aat-layout-trak-table.hh"