[OT] Port Arabic fallback shaping to synthetic GSUB

All of init/medi/fina/isol and rlig implemented.

Let there be dragons... ⻯

src/hb-ot-shape-complex-arabic-fallback.hh

diff --git a/src/hb-ot-shape-complex-arabic-fallback.hh b/src/hb-ot-shape-complex-arabic-fallback.hh
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+++ b/src/hb-ot-shape-complex-arabic-fallback.hh
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+/*
+ * Copyright © 2012  Google, Inc.
+ *
+ *  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.
+ *
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#ifndef HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH
+#define HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH
+
+#include "hb-private.hh"
+
+#include "hb-ot-shape-private.hh"
+#include "hb-ot-layout-gsub-table.hh"
+
+
+static const hb_tag_t arabic_fallback_features[] =
+{
+  HB_TAG('i','n','i','t'),
+  HB_TAG('m','e','d','i'),
+  HB_TAG('f','i','n','a'),
+  HB_TAG('i','s','o','l'),
+  HB_TAG('r','l','i','g'),
+};
+
+/* Same order as the fallback feature array */
+enum {
+  FALLBACK_INIT,
+  FALLBACK_MEDI,
+  FALLBACK_FINA,
+  FALLBACK_ISOL,
+  FALLBACK_RLIG,
+  ARABIC_NUM_FALLBACK_FEATURES
+};
+
+static OT::SubstLookup *
+arabic_fallback_synthesize_lookup_single (const hb_ot_shape_plan_t *plan,
+					  hb_font_t *font,
+					  unsigned int feature_index)
+{
+  OT::GlyphID glyphs[SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1];
+  OT::GlyphID substitutes[SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1];
+  unsigned int num_glyphs = 0;
+
+  /* Populate arrays */
+  for (hb_codepoint_t u = SHAPING_TABLE_FIRST; u < SHAPING_TABLE_LAST + 1; u++)
+  {
+    hb_codepoint_t s = shaping_table[u - SHAPING_TABLE_FIRST][feature_index];
+    hb_codepoint_t u_glyph, s_glyph;
+
+    if (u == s ||
+	!hb_font_get_glyph (font, u, 0, &u_glyph) ||
+	!hb_font_get_glyph (font, s, 0, &s_glyph) ||
+	u_glyph == s_glyph ||
+	u_glyph > 0xFFFF || s_glyph > 0xFFFF)
+      continue;
+
+    glyphs[num_glyphs].set (u_glyph);
+    substitutes[num_glyphs].set (s_glyph);
+
+    num_glyphs++;
+  }
+
+  /* Bubble-sort!
+   * May not be good-enough for presidential candidate interviews, but good-enough for us... */
+  hb_bubble_sort (&glyphs[0], num_glyphs, OT::GlyphID::cmp, &substitutes[0]);
+
+  OT::Supplier<OT::GlyphID> glyphs_supplier      (glyphs, num_glyphs);
+  OT::Supplier<OT::GlyphID> substitutes_supplier (substitutes, num_glyphs);
+
+  /* Each glyph takes four bytes max, and there's some overhead. */
+  char buf[(SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1) * 4 + 128];
+  OT::hb_serialize_context_t c (buf, sizeof (buf));
+  OT::SubstLookup *lookup = c.start_serialize<OT::SubstLookup> ();
+  bool ret = lookup->serialize_single (&c,
+				       OT::LookupFlag::IgnoreMarks,
+				       glyphs_supplier,
+				       substitutes_supplier,
+				       num_glyphs);
+  c.end_serialize ();
+  /* TODO sanitize the results? */
+
+  return ret ? c.copy<OT::SubstLookup> () : NULL;
+}
+
+static OT::SubstLookup *
+arabic_fallback_synthesize_lookup_ligature (const hb_ot_shape_plan_t *plan,
+					    hb_font_t *font)
+{
+  OT::GlyphID first_glyphs[ARRAY_LENGTH_CONST (ligature_table)];
+  unsigned int first_glyphs_indirection[ARRAY_LENGTH_CONST (ligature_table)];
+  unsigned int ligature_per_first_glyph_count_list[ARRAY_LENGTH_CONST (first_glyphs)];
+  unsigned int num_first_glyphs = 0;
+
+  /* We know that all our ligatures are 2-component */
+  OT::GlyphID ligatures_list[ARRAY_LENGTH_CONST (first_glyphs) * ARRAY_LENGTH_CONST(ligature_table[0].ligatures)];
+  unsigned int component_count_list[ARRAY_LENGTH_CONST (ligatures_list)];
+  OT::GlyphID component_list[ARRAY_LENGTH_CONST (ligatures_list) * 1/* One extra component per ligature */];
+  unsigned int num_ligatures = 0;
+
+  /* Populate arrays */
+
+  /* Sort out the first-glyphs */
+  for (unsigned int first_glyph_idx = 0; first_glyph_idx < ARRAY_LENGTH (first_glyphs); first_glyph_idx++)
+  {
+    hb_codepoint_t first_u = ligature_table[first_glyph_idx].first;
+    hb_codepoint_t first_glyph;
+    if (!hb_font_get_glyph (font, first_u, 0, &first_glyph))
+      continue;
+    first_glyphs[num_first_glyphs].set (first_glyph);
+    ligature_per_first_glyph_count_list[num_first_glyphs] = 0;
+    first_glyphs_indirection[num_first_glyphs] = first_glyph_idx;
+    num_first_glyphs++;
+  }
+  hb_bubble_sort (&first_glyphs[0], num_first_glyphs, OT::GlyphID::cmp, &first_glyphs_indirection[0]);
+
+  /* Now that the first-glyphs are sorted, walk again, populate ligatures. */
+  for (unsigned int i = 0; i < num_first_glyphs; i++)
+  {
+    unsigned int first_glyph_idx = first_glyphs_indirection[i];
+
+    for (unsigned int second_glyph_idx = 0; second_glyph_idx < ARRAY_LENGTH (ligature_table[0].ligatures); second_glyph_idx++)
+    {
+      hb_codepoint_t second_u   = ligature_table[first_glyph_idx].ligatures[second_glyph_idx].second;
+      hb_codepoint_t ligature_u = ligature_table[first_glyph_idx].ligatures[second_glyph_idx].ligature;
+      hb_codepoint_t second_glyph, ligature_glyph;
+      if (!second_u ||
+	  !hb_font_get_glyph (font, second_u,   0, &second_glyph) ||
+	  !hb_font_get_glyph (font, ligature_u, 0, &ligature_glyph))
+	continue;
+
+      ligature_per_first_glyph_count_list[i]++;
+
+      ligatures_list[num_ligatures].set (ligature_glyph);
+      component_count_list[num_ligatures] = 2;
+      component_list[num_ligatures].set (second_glyph);
+      num_ligatures++;
+    }
+  }
+
+  OT::Supplier<OT::GlyphID>   first_glyphs_supplier                      (first_glyphs, num_first_glyphs);
+  OT::Supplier<unsigned int > ligature_per_first_glyph_count_supplier    (ligature_per_first_glyph_count_list, num_first_glyphs);
+  OT::Supplier<OT::GlyphID>   ligatures_supplier                         (ligatures_list, num_ligatures);
+  OT::Supplier<unsigned int > component_count_supplier                   (component_count_list, num_ligatures);
+  OT::Supplier<OT::GlyphID>   component_supplier                         (component_list, num_ligatures);
+
+  char buf[2048];
+  OT::hb_serialize_context_t c (buf, sizeof (buf));
+  OT::SubstLookup *lookup = c.start_serialize<OT::SubstLookup> ();
+  bool ret = lookup->serialize_ligature (&c,
+					 OT::LookupFlag::IgnoreMarks,
+					 first_glyphs_supplier,
+					 ligature_per_first_glyph_count_supplier,
+					 num_first_glyphs,
+					 ligatures_supplier,
+					 component_count_supplier,
+					 component_supplier);
+
+  c.end_serialize ();
+  /* TODO sanitize the results? */
+
+  return ret ? c.copy<OT::SubstLookup> () : NULL;
+}
+
+static OT::SubstLookup *
+arabic_fallback_synthesize_lookup (const hb_ot_shape_plan_t *plan,
+				   hb_font_t *font,
+				   unsigned int feature_index)
+{
+  if (feature_index < 4)
+    return arabic_fallback_synthesize_lookup_single (plan, font, feature_index);
+  else
+    return arabic_fallback_synthesize_lookup_ligature (plan, font);
+}
+
+struct arabic_fallback_plan_t
+{
+  ASSERT_POD ();
+
+  hb_mask_t mask_array[ARABIC_NUM_FALLBACK_FEATURES];
+  OT::SubstLookup *lookup_array[ARABIC_NUM_FALLBACK_FEATURES];
+  hb_set_digest_t digest_array[ARABIC_NUM_FALLBACK_FEATURES];
+};
+
+static const arabic_fallback_plan_t arabic_fallback_plan_nil = {};
+
+static arabic_fallback_plan_t *
+arabic_fallback_plan_create (const hb_ot_shape_plan_t *plan,
+			     hb_font_t *font)
+{
+  arabic_fallback_plan_t *fallback_plan = (arabic_fallback_plan_t *) calloc (1, sizeof (arabic_fallback_plan_t));
+  if (unlikely (!fallback_plan))
+    return const_cast<arabic_fallback_plan_t *> (&arabic_fallback_plan_nil);
+
+  for (unsigned int i = 0; i < ARABIC_NUM_FALLBACK_FEATURES; i++) {
+    fallback_plan->mask_array[i] = plan->map.get_1_mask (arabic_fallback_features[i]);
+    if (fallback_plan->mask_array[i]) {
+      fallback_plan->lookup_array[i] = arabic_fallback_synthesize_lookup (plan, font, i);
+      if (fallback_plan->lookup_array[i])
+	fallback_plan->lookup_array[i]->add_coverage (&fallback_plan->digest_array[i]);
+    }
+  }
+
+  return fallback_plan;
+}
+
+static void
+arabic_fallback_plan_destroy (arabic_fallback_plan_t *fallback_plan)
+{
+  if (!fallback_plan || fallback_plan == &arabic_fallback_plan_nil)
+    return;
+
+  for (unsigned int i = 0; i < ARABIC_NUM_FALLBACK_FEATURES; i++)
+    if (fallback_plan->lookup_array[i])
+      free (fallback_plan->lookup_array[i]);
+
+  free (fallback_plan);
+}
+
+static void
+arabic_fallback_plan_shape (arabic_fallback_plan_t *fallback_plan,
+			    hb_font_t *font,
+			    hb_buffer_t *buffer)
+{
+  for (unsigned int i = 0; i < ARABIC_NUM_FALLBACK_FEATURES; i++)
+    if (fallback_plan->lookup_array[i]) {
+      OT::hb_apply_context_t c (font, buffer, fallback_plan->mask_array[i]);
+      fallback_plan->lookup_array[i]->apply_string (&c, &fallback_plan->digest_array[i]);
+    }
+}
+
+
+#endif /* HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH */