1 files changed, 229 insertions, 0 deletions
diff --git a/gfx/harfbuzz/src/gen-vowel-constraints.py b/gfx/harfbuzz/src/gen-vowel-constraints.py
new file mode 100755
index 0000000000..3c1f6211eb
--- /dev/null
+++ b/gfx/harfbuzz/src/gen-vowel-constraints.py
@@ -0,0 +1,229 @@
+#!/usr/bin/env python3
+
+"""Generator of the function to prohibit certain vowel sequences.
+
+It creates ``_hb_preprocess_text_vowel_constraints``, which inserts dotted
+circles into sequences prohibited by the USE script development spec.
+This function should be used as the ``preprocess_text`` of an
+``hb_ot_shaper_t``.
+
+usage: ./gen-vowel-constraints.py ms-use/IndicShapingInvalidCluster.txt Scripts.txt
+
+Input file:
+* https://unicode.org/Public/UCD/latest/ucd/Scripts.txt
+"""
+
+import collections
+def write (s):
+	sys.stdout.flush ()
+	sys.stdout.buffer.write (s.encode ('utf-8'))
+import sys
+
+if len (sys.argv) != 3:
+	sys.exit (__doc__)
+
+with open (sys.argv[2], encoding='utf-8') as f:
+	scripts_header = [f.readline () for i in range (2)]
+	scripts = {}
+	script_order = {}
+	for line in f:
+		j = line.find ('#')
+		if j >= 0:
+			line = line[:j]
+		fields = [x.strip () for x in line.split (';')]
+		if len (fields) == 1:
+			continue
+		uu = fields[0].split ('..')
+		start = int (uu[0], 16)
+		if len (uu) == 1:
+			end = start
+		else:
+			end = int (uu[1], 16)
+		script = fields[1]
+		for u in range (start, end + 1):
+			scripts[u] = script
+		if script not in script_order:
+			script_order[script] = start
+
+class ConstraintSet (object):
+	"""A set of prohibited code point sequences.
+
+	Args:
+		constraint (List[int]): A prohibited code point sequence.
+
+	"""
+	def __init__ (self, constraint):
+		# Either a list or a dictionary. As a list of code points, it
+		# represents a prohibited code point sequence. As a dictionary,
+		# it represents a set of prohibited sequences, where each item
+		# represents the set of prohibited sequences starting with the
+		# key (a code point) concatenated with any of the values
+		# (ConstraintSets).
+		self._c = constraint
+
+	def add (self, constraint):
+		"""Add a constraint to this set."""
+		if not constraint:
+			return
+		first = constraint[0]
+		rest = constraint[1:]
+		if isinstance (self._c, list):
+			if constraint == self._c[:len (constraint)]:
+				self._c = constraint
+			elif self._c != constraint[:len (self._c)]:
+				self._c = {self._c[0]: ConstraintSet (self._c[1:])}
+		if isinstance (self._c, dict):
+			if first in self._c:
+				self._c[first].add (rest)
+			else:
+				self._c[first] = ConstraintSet (rest)
+
+	@staticmethod
+	def _indent (depth):
+		return ('  ' * depth).replace ('        ', '\t')
+
+	def __str__ (self, index=0, depth=4):
+		s = []
+		indent = self._indent (depth)
+		if isinstance (self._c, list):
+			if len (self._c) == 0:
+				assert index == 2, 'Cannot use `matched` for this constraint; the general case has not been implemented'
+				s.append ('{}matched = true;\n'.format (indent))
+			elif len (self._c) == 1:
+				assert index == 1, 'Cannot use `matched` for this constraint; the general case has not been implemented'
+				s.append ('{}matched = 0x{:04X}u == buffer->cur ({}).codepoint;\n'.format (indent, next (iter (self._c)), index or ''))
+			else:
+				s.append ('{}if (0x{:04X}u == buffer->cur ({}).codepoint &&\n'.format (indent, self._c[0], index or ''))
+				if index:
+					s.append ('{}buffer->idx + {} < count &&\n'.format (self._indent (depth + 2), index + 1))
+				for i, cp in enumerate (self._c[1:], start=1):
+					s.append ('{}0x{:04X}u == buffer->cur ({}).codepoint{}\n'.format (
+						self._indent (depth + 2), cp, index + i, ')' if i == len (self._c) - 1 else ' &&'))
+				s.append ('{}{{\n'.format (indent))
+				for i in range (index):
+					s.append ('{}(void) buffer->next_glyph ();\n'.format (self._indent (depth + 1)))
+				s.append ('{}matched = true;\n'.format (self._indent (depth + 1)))
+				s.append ('{}}}\n'.format (indent))
+		else:
+			s.append ('{}switch (buffer->cur ({}).codepoint)\n'.format(indent, index or ''))
+			s.append ('{}{{\n'.format (indent))
+			cases = collections.defaultdict (set)
+			for first, rest in sorted (self._c.items ()):
+				cases[rest.__str__ (index + 1, depth + 2)].add (first)
+			for body, labels in sorted (cases.items (), key=lambda b_ls: sorted (b_ls[1])[0]):
+				for i, cp in enumerate (sorted (labels)):
+					if i % 4 == 0:
+						s.append (self._indent (depth + 1))
+					else:
+						s.append (' ')
+					s.append ('case 0x{:04X}u:{}'.format (cp, '\n' if i % 4 == 3 else ''))
+				if len (labels) % 4 != 0:
+					s.append ('\n')
+				s.append (body)
+				s.append ('{}break;\n'.format (self._indent (depth + 2)))
+			s.append ('{}}}\n'.format (indent))
+		return ''.join (s)
+
+constraints = {}
+with open (sys.argv[1], encoding='utf-8') as f:
+	constraints_header = []
+	while True:
+		line = f.readline ().strip ()
+		if line == '#':
+			break
+		constraints_header.append(line)
+	for line in f:
+		j = line.find ('#')
+		if j >= 0:
+			line = line[:j]
+		constraint = [int (cp, 16) for cp in line.split (';')[0].split ()]
+		if not constraint: continue
+		assert 2 <= len (constraint), 'Prohibited sequence is too short: {}'.format (constraint)
+		script = scripts[constraint[0]]
+		if script in constraints:
+			constraints[script].add (constraint)
+		else:
+			constraints[script] = ConstraintSet (constraint)
+		assert constraints, 'No constraints found'
+
+print ('/* == Start of generated functions == */')
+print ('/*')
+print (' * The following functions are generated by running:')
+print (' *')
+print (' *   %s ms-use/IndicShapingInvalidCluster.txt Scripts.txt' % sys.argv[0])
+print (' *')
+print (' * on files with these headers:')
+print (' *')
+for line in constraints_header:
+	print (' * %s' % line.strip ())
+print (' *')
+for line in scripts_header:
+	print (' * %s' % line.strip ())
+print (' */')
+
+print ()
+print ('#include "hb.hh"')
+print ()
+print ('#ifndef HB_NO_OT_SHAPE')
+print ()
+print ('#include "hb-ot-shaper-vowel-constraints.hh"')
+print ()
+print ('static void')
+print ('_output_dotted_circle (hb_buffer_t *buffer)')
+print ('{')
+print ('  (void) buffer->output_glyph (0x25CCu);')
+print ('  _hb_glyph_info_reset_continuation (&buffer->prev());')
+print ('}')
+print ()
+print ('static void')
+print ('_output_with_dotted_circle (hb_buffer_t *buffer)')
+print ('{')
+print ('  _output_dotted_circle (buffer);')
+print ('  (void) buffer->next_glyph ();')
+print ('}')
+print ()
+
+print ('void')
+print ('_hb_preprocess_text_vowel_constraints (const hb_ot_shape_plan_t *plan HB_UNUSED,')
+print ('\t\t\t\t       hb_buffer_t              *buffer,')
+print ('\t\t\t\t       hb_font_t                *font HB_UNUSED)')
+print ('{')
+print ('#ifdef HB_NO_OT_SHAPER_VOWEL_CONSTRAINTS')
+print ('  return;')
+print ('#endif')
+print ('  if (buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE)')
+print ('    return;')
+print ()
+print ('  /* UGLY UGLY UGLY business of adding dotted-circle in the middle of')
+print ('   * vowel-sequences that look like another vowel.  Data for each script')
+print ('   * collected from the USE script development spec.')
+print ('   *')
+print ('   * https://github.com/harfbuzz/harfbuzz/issues/1019')
+print ('   */')
+print ('  buffer->clear_output ();')
+print ('  unsigned int count = buffer->len;')
+print ('  switch ((unsigned) buffer->props.script)')
+print ('  {')
+
+for script, constraints in sorted (constraints.items (), key=lambda s_c: script_order[s_c[0]]):
+	print ('    case HB_SCRIPT_{}:'.format (script.upper ()))
+	print ('      for (buffer->idx = 0; buffer->idx + 1 < count && buffer->successful;)')
+	print ('      {')
+	print ('\tbool matched = false;')
+	write (str (constraints))
+	print ('\t(void) buffer->next_glyph ();')
+	print ('\tif (matched) _output_with_dotted_circle (buffer);')
+	print ('      }')
+	print ('      break;')
+	print ()
+
+print ('    default:')
+print ('      break;')
+print ('  }')
+print ('  buffer->sync ();')
+print ('}')
+
+print ()
+print ()
+print ('#endif')
+print ('/* == End of generated functions == */')