text: # ----------------------------------------------------------------------------
  # pyglet
  # Copyright (c) 2006-2008 Alex Holkner
  # Copyright (c) 2008-2021 pyglet contributors
  # All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  #
  #  * Redistributions of source code must retain the above copyright
  #    notice, this list of conditions and the following disclaimer.
  #  * Redistributions in binary form must reproduce the above copyright
  #    notice, this list of conditions and the following disclaimer in
  #    the documentation and/or other materials provided with the
  #    distribution.
  #  * Neither the name of pyglet nor the names of its
  #    contributors may be used to endorse or promote products
  #    derived from this software without specific prior written
  #    permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  # FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  # COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  # POSSIBILITY OF SUCH DAMAGE.
  # ----------------------------------------------------------------------------
  
  """Render simple text and formatted documents efficiently.
  
  Three layout classes are provided:
  
  :py:class:`~pyglet.text.layout.TextLayout`
      The entire document is laid out before it is rendered.  The layout will
      be grouped with other layouts in the same batch (allowing for efficient
      rendering of multiple layouts).
  
      Any change to the layout or document,
      and even querying some properties, will cause the entire document
      to be laid out again.
  
  :py:class:`~pyglet.text.layout.ScrollableTextLayout`
      Based on :py:func:`~pyglet.text.layout.TextLayout`.
  
      A separate group is used for layout which crops the contents of the
      layout to the layout rectangle.  Additionally, the contents of the
      layout can be "scrolled" within that rectangle with the ``view_x`` and
      ``view_y`` properties.
  
  :py:class:`~pyglet.text.layout.IncrementalTextLayout`
      Based on :py:class:`~pyglet.text.layout.ScrollableTextLayout`.
  
      When the layout or document are modified, only the affected regions
      are laid out again.  This permits efficient interactive editing and
      styling of text.
  
      Only the visible portion of the layout is actually rendered; as the
      viewport is scrolled additional sections are rendered and discarded as
      required.  This permits efficient viewing and editing of large documents.
  
      Additionally, this class provides methods for locating the position of a
      caret in the document, and for displaying interactive text selections.
  
  All three layout classes can be used with either :py:class:`~pyglet.text.document.UnformattedDocument` or
  :py:class:`~pyglet.text.document.FormattedDocument`, and can be either single-line or ``multiline``.  The
  combinations of these options effectively provides 12 different text display
  possibilities.
  
  Style attributes
  ================
  
  The following character style attribute names are recognised by the layout
  classes.  Data types and units are as specified.
  
  Where an attribute is marked "as a distance" the value is assumed to be
  in pixels if given as an int or float, otherwise a string of the form
  ``"0u"`` is required, where ``0`` is the distance and ``u`` is the unit; one
  of ``"px"`` (pixels), ``"pt"`` (points), ``"pc"`` (picas), ``"cm"``
  (centimeters), ``"mm"`` (millimeters) or ``"in"`` (inches).  For example,
  ``"14pt"`` is the distance covering 14 points, which at the default DPI of 96
  is 18 pixels.
  
  ``font_name``
      Font family name, as given to :py:func:`pyglet.font.load`.
  ``font_size``
      Font size, in points.
  ``bold``
      Boolean.
  ``italic``
      Boolean.
  ``underline``
      4-tuple of ints in range (0, 255) giving RGBA underline color, or None
      (default) for no underline.
  ``kerning``
      Additional space to insert between glyphs, as a distance.  Defaults to 0.
  ``baseline``
      Offset of glyph baseline from line baseline, as a distance.  Positive
      values give a superscript, negative values give a subscript.  Defaults to
      0.
  ``color``
      4-tuple of ints in range (0, 255) giving RGBA text color
  ``background_color``
      4-tuple of ints in range (0, 255) giving RGBA text background color; or
      ``None`` for no background fill.
  
  The following paragraph style attribute names are recognised.  Note
  that paragraph styles are handled no differently from character styles by the
  document: it is the application's responsibility to set the style over an
  entire paragraph, otherwise results are undefined.
  
  ``align``
      ``left`` (default), ``center`` or ``right``.
  ``indent``
      Additional horizontal space to insert before the first glyph of the
      first line of a paragraph, as a distance.
  ``leading``
      Additional space to insert between consecutive lines within a paragraph,
      as a distance.  Defaults to 0.
  ``line_spacing``
      Distance between consecutive baselines in a paragraph, as a distance.
      Defaults to ``None``, which automatically calculates the tightest line
      spacing for each line based on the font ascent and descent.
  ``margin_left``
      Left paragraph margin, as a distance.
  ``margin_right``
      Right paragraph margin, as a distance.
  ``margin_top``
      Margin above paragraph, as a distance.
  ``margin_bottom``
      Margin below paragraph, as a distance.  Adjacent margins do not collapse.
  ``tab_stops``
      List of horizontal tab stops, as distances, measured from the left edge of
      the text layout.  Defaults to the empty list.  When the tab stops
      are exhausted, they implicitly continue at 50 pixel intervals.
  ``wrap``
      ``char``, ``word``, True (default) or False.  The boundaries at which to
      wrap text to prevent it overflowing a line.  With ``char``, the line
      wraps anywhere in the text; with ``word`` or True, the line wraps at
      appropriate boundaries between words; with False the line does not wrap,
      and may overflow the layout width.  ``char`` and ``word`` styles are
      since pyglet 1.2.
  
  Other attributes can be used to store additional style information within the
  document; they will be ignored by the built-in text classes.
  
  .. versionadded:: 1.1
  """
  
  import re
  import sys
  
  import pyglet
  
  from pyglet import graphics
  from pyglet.gl import *
  from pyglet.event import EventDispatcher
  from pyglet.text import runlist
  from pyglet.graphics import shader
  from pyglet.font.base import grapheme_break
  
  _is_pyglet_doc_run = hasattr(sys, "is_pyglet_doc_run") and sys.is_pyglet_doc_run
  
  _distance_re = re.compile(r'([-0-9.]+)([a-zA-Z]+)')
  
  
  def _parse_distance(distance, dpi):
      """Parse a distance string and return corresponding distance in pixels as
      an integer.
      """
      if isinstance(distance, int):
          return distance
      elif isinstance(distance, float):
          return int(distance)
  
      match = _distance_re.match(distance)
      assert match, 'Could not parse distance %s' % distance
      if not match:
          return 0
  
      value, unit = match.groups()
      value = float(value)
      if unit == 'px':
          return int(value)
      elif unit == 'pt':
          return int(value * dpi / 72.0)
      elif unit == 'pc':
          return int(value * dpi / 6.0)
      elif unit == 'in':
          return int(value * dpi)
      elif unit == 'mm':
          return int(value * dpi * 0.0393700787)
      elif unit == 'cm':
          return int(value * dpi * 0.393700787)
      else:
          assert False, 'Unknown distance unit %s' % unit
  
  
  class _Line:
      align = 'left'
  
      margin_left = 0
      margin_right = 0
  
      length = 0
  
      ascent = 0
      descent = 0
      width = 0
      paragraph_begin = False
      paragraph_end = False
  
      x = None
      y = None
  
      def __init__(self, start):
          self.vertex_lists = []
          self.start = start
          self.boxes = []
  
      def __repr__(self):
          return '_Line(%r)' % self.boxes
  
      def add_box(self, box):
          self.boxes.append(box)
          self.length += box.length
          self.ascent = max(self.ascent, box.ascent)
          self.descent = min(self.descent, box.descent)
          self.width += box.advance
  
      def delete(self, layout):
          for vertex_list in self.vertex_lists:
              vertex_list.delete()
          self.vertex_lists = []
  
          for box in self.boxes:
              box.delete(layout)
  
  
  class _LayoutContext:
      def __init__(self, layout, document, colors_iter, background_iter):
          self.colors_iter = colors_iter
          underline_iter = document.get_style_runs('underline')
          self.decoration_iter = runlist.ZipRunIterator((background_iter, underline_iter))
          self.baseline_iter = runlist.FilteredRunIterator(
              document.get_style_runs('baseline'),
              lambda value: value is not None, 0)
  
  
  class _StaticLayoutContext(_LayoutContext):
      def __init__(self, layout, document, colors_iter, background_iter):
          super().__init__(layout, document, colors_iter, background_iter)
          self.vertex_lists = layout._vertex_lists
          self.boxes = layout._boxes
  
      def add_list(self, vertex_list):
          self.vertex_lists.append(vertex_list)
  
      def add_box(self, box):
          self.boxes.append(box)
  
  
  class _IncrementalLayoutContext(_LayoutContext):
      line = None
  
      def add_list(self, vertex_list):
          self.line.vertex_lists.append(vertex_list)
  
      def add_box(self, box):
          pass
  
  
  class _AbstractBox:
      owner = None
  
      def __init__(self, ascent, descent, advance, length):
          self.ascent = ascent
          self.descent = descent
          self.advance = advance
          self.length = length
  
      def place(self, layout, i, x, y, context):
          raise NotImplementedError('abstract')
  
      def delete(self, layout):
          raise NotImplementedError('abstract')
  
      def get_position_in_box(self, x):
          raise NotImplementedError('abstract')
  
      def get_point_in_box(self, position):
          raise NotImplementedError('abstract')
  
  
  class _GlyphBox(_AbstractBox):
      def __init__(self, owner, font, glyphs, advance):
          """Create a run of glyphs sharing the same texture.
  
          :Parameters:
              `owner` : `pyglet.image.Texture`
                  Texture of all glyphs in this run.
              `font` : `pyglet.font.base.Font`
                  Font of all glyphs in this run.
              `glyphs` : list of (int, `pyglet.font.base.Glyph`)
                  Pairs of ``(kern, glyph)``, where ``kern`` gives horizontal
                  displacement of the glyph in pixels (typically 0).
              `advance` : int
                  Width of glyph run; must correspond to the sum of advances
                  and kerns in the glyph list.
  
          """
          super().__init__(font.ascent, font.descent, advance, len(glyphs))
          assert owner
          self.owner = owner
          self.font = font
          self.glyphs = glyphs
          self.advance = advance
  
      def place(self, layout, i, x, y, context):
          assert self.glyphs
          try:
              group = layout.groups[self.owner]
          except KeyError:
              group = layout.default_group_class(texture=self.owner, order=1, program=get_default_layout_shader())
              layout.groups[self.owner] = group
  
          n_glyphs = self.length
          vertices = []
          tex_coords = []
          baseline = 0
          x1 = x
          for start, end, baseline in context.baseline_iter.ranges(i, i + n_glyphs):
              baseline = layout.parse_distance(baseline)
              assert len(self.glyphs[start - i:end - i]) == end - start
              for kern, glyph in self.glyphs[start - i:end - i]:
                  x1 += kern
                  v0, v1, v2, v3 = glyph.vertices
                  v0 += x1
                  v2 += x1
                  v1 += y + baseline
                  v3 += y + baseline
                  vertices.extend(map(int, [v0, v1, v2, v1, v2, v3, v0, v3]))
                  t = glyph.tex_coords
                  tex_coords.extend(t)
                  x1 += glyph.advance
  
          # Text color
          colors = []
          for start, end, color in context.colors_iter.ranges(i, i + n_glyphs):
              if color is None:
                  color = (0, 0, 0, 255)
              colors.extend(color * ((end - start) * 4))
  
          indices = []
          # Create indices for each glyph quad:
          for i in range(n_glyphs):
              indices.extend([element + (i * 4) for element in [0, 1, 2, 0, 2, 3]])
  
          vertex_list = layout.batch.add_indexed(n_glyphs * 4, GL_TRIANGLES, group,
                                                 indices,
                                                 ('vertices2f/dynamic', vertices),
                                                 ('colors4Bn/dynamic', colors),
                                                 ('tex_coords3f/dynamic', tex_coords),
                                                 'translation2f/dynamic')
  
          context.add_list(vertex_list)
  
          # Decoration (background color and underline)
          # -------------------------------------------
          # Should iterate over baseline too, but in practice any sensible
          # change in baseline will correspond with a change in font size,
          # and thus glyph run as well.  So we cheat and just use whatever
          # baseline was seen last.
          background_vertices = []
          background_colors = []
          underline_vertices = []
          underline_colors = []
          y1 = y + self.descent + baseline
          y2 = y + self.ascent + baseline
          x1 = x
          for start, end, decoration in context.decoration_iter.ranges(i, i + n_glyphs):
              bg, underline = decoration
              x2 = x1
              for kern, glyph in self.glyphs[start - i:end - i]:
                  x2 += glyph.advance + kern
  
              if bg is not None:
                  background_vertices.extend([x1, y1, x2, y1, x2, y2, x1, y2])
                  background_colors.extend(bg * 4)
  
              if underline is not None:
                  underline_vertices.extend([x1, y + baseline - 2, x2, y + baseline - 2])
                  underline_colors.extend(underline * 2)
  
              x1 = x2
  
          if background_vertices:
              background_list = layout.batch.add_indexed(len(background_vertices) // 2,
                                                         GL_TRIANGLES, layout.background_decoration_group,
                                                         [0, 1, 2, 0, 2, 3],
                                                         ('vertices2f/dynamic', background_vertices),
                                                         ('colors4Bn/dynamic', background_colors),
                                                         'translation2f/dynamic')
              context.add_list(background_list)
  
          if underline_vertices:
              underline_list = layout.batch.add(len(underline_vertices) // 2,
                                                GL_LINES, layout.foreground_decoration_group,
                                                ('vertices2f/dynamic', underline_vertices),
                                                ('colors4Bn/dynamic', underline_colors),
                                                'translation2f/dynamic')
              context.add_list(underline_list)
  
      def delete(self, layout):
          pass
  
      def get_point_in_box(self, position):
          x = 0
          for (kern, glyph) in self.glyphs:
              if position == 0:
                  break
              position -= 1
              x += glyph.advance + kern
          return x
  
      def get_position_in_box(self, x):
          position = 0
          last_glyph_x = 0
          for kern, glyph in self.glyphs:
              last_glyph_x += kern
              if last_glyph_x + glyph.advance // 2 > x:
                  return position
              position += 1
              last_glyph_x += glyph.advance
          return position
  
      def __repr__(self):
          return '_GlyphBox(%r)' % self.glyphs
  
  
  class _InlineElementBox(_AbstractBox):
      def __init__(self, element):
          """Create a glyph run holding a single element.
          """
          super().__init__(element.ascent, element.descent, element.advance, 1)
          self.element = element
          self.placed = False
  
      def place(self, layout, i, x, y, context):
          self.element.place(layout, x, y)
          self.placed = True
          context.add_box(self)
  
      def delete(self, layout):
          # font == element
          if self.placed:
              self.element.remove(layout)
              self.placed = False
  
      def get_point_in_box(self, position):
          if position == 0:
              return 0
          else:
              return self.advance
  
      def get_position_in_box(self, x):
          if x < self.advance // 2:
              return 0
          else:
              return 1
  
      def __repr__(self):
          return '_InlineElementBox(%r)' % self.element
  
  
  class _InvalidRange:
      # Used by the IncrementalTextLayout
  
      def __init__(self):
          self.start = sys.maxsize
          self.end = 0
  
      def insert(self, start, length):
          if self.start >= start:
              self.start += length
          if self.end >= start:
              self.end += length
          self.invalidate(start, start + length)
  
      def delete(self, start, end):
          if self.start > end:
              self.start -= end - start
          elif self.start > start:
              self.start = start
          if self.end > end:
              self.end -= end - start
          elif self.end > start:
              self.end = start
  
      def invalidate(self, start, end):
          if end <= start:
              return
          self.start = min(self.start, start)
          self.end = max(self.end, end)
  
      def validate(self):
          start, end = self.start, self.end
          self.start = sys.maxsize
          self.end = 0
          return start, end
  
      def is_invalid(self):
          return self.end > self.start
  
  
  layout_vertex_source = """#version 330 core
      in vec2 vertices;
      in vec4 colors;
      in vec3 tex_coords;
      in vec2 translation;
  
      out vec4 text_colors;
      out vec2 texture_coords;
      out vec4 position;
  
      uniform WindowBlock
      {
          mat4 projection;
          mat4 view;
      } window;
  
      void main()
      {
          mat4 translate_mat = mat4(1.0);
          translate_mat[3] = vec4(translation, 1.0, 1.0);
  
          gl_Position = window.projection * window.view * translate_mat * vec4(vertices, 0, 1);
  
          position = vec4(vertices + translation, 0, 1);
          text_colors = colors;
          texture_coords = tex_coords.xy;
      }
  """
  
  layout_fragment_source = """#version 330 core
      in vec4 text_colors;
      in vec2 texture_coords;
      in vec4 position;
  
      out vec4 final_colors;
  
      uniform sampler2D text;
      uniform bool scissor = false;
      uniform vec4 scissor_area;
  
      void main()
      {   
          final_colors = vec4(text_colors.rgb, texture(text, texture_coords).a) * text_colors;
          if (scissor == true) {
              if (position.x < scissor_area[0]) discard;                     // left
              if (position.y < scissor_area[1]) discard;                     // bottom
              if (position.x > scissor_area[0] + scissor_area[2]) discard;   // right
              if (position.y > scissor_area[1] + scissor_area[3]) discard;   // top
          }
      }
  """
  
  decoration_vertex_source = """#version 330 core
      in vec2 vertices;
      in vec4 colors;
      in vec2 translation;
  
      out vec4 vert_colors;
      out vec4 position;
  
  
      uniform WindowBlock
      {
          mat4 projection;
          mat4 view;
      } window;
  
      void main()
      {
          mat4 translate_mat = mat4(1.0);
          translate_mat[3] = vec4(translation, 1.0, 1.0);
  
          gl_Position = window.projection * window.view * translate_mat * vec4(vertices, 0, 0);
  
          position = vec4(vertices + translation, 0, 1);
          vert_colors = colors;
      }
  """
  
  decoration_fragment_source = """#version 330 core
      in vec4 vert_colors;
      in vec4 position;
  
      out vec4 final_colors;
  
      uniform bool scissor = false;
      uniform vec4 scissor_area;
  
      void main()
      {   
          final_colors = vert_colors;
          if (scissor == true) {
              if (position.x < scissor_area[0]) discard;                     // left
              if (position.y < scissor_area[1]) discard;                     // bottom
              if (position.x > scissor_area[0] + scissor_area[2]) discard;   // right
              if (position.y > scissor_area[1] + scissor_area[3]) discard;   // top
          }
      }
  """
  
  
  def get_default_layout_shader():
      try:
          return pyglet.gl.current_context.pyglet_text_layout_shader
      except AttributeError:
          _default_vert_shader = shader.Shader(layout_vertex_source, 'vertex')
          _default_frag_shader = shader.Shader(layout_fragment_source, 'fragment')
          default_shader_program = shader.ShaderProgram(_default_vert_shader, _default_frag_shader)
          pyglet.gl.current_context.pyglet_text_layout_shader = default_shader_program
          return pyglet.gl.current_context.pyglet_text_layout_shader
  
  
  def get_default_decoration_shader():
      try:
          return pyglet.gl.current_context.pyglet_text_decoration_shader
      except AttributeError:
          _default_vert_shader = shader.Shader(decoration_vertex_source, 'vertex')
          _default_frag_shader = shader.Shader(decoration_fragment_source, 'fragment')
          default_shader_program = shader.ShaderProgram(_default_vert_shader, _default_frag_shader)
          pyglet.gl.current_context.pyglet_text_decoration_shader = default_shader_program
          return pyglet.gl.current_context.pyglet_text_decoration_shader
  
  
  class TextLayoutGroup(graphics.Group):
      def __init__(self, texture, order=1, program=None):
          """Create a text layout rendering group.
  
          The group is created internally when a :py:class:`~pyglet.text.Label`
          is created; applications usually do not need to explicitly create it.
          """
          super().__init__(order=order)
          self.texture = texture
          self.program = program or get_default_layout_shader()
  
      def set_state(self):
          self.program.use()
          self.program['scissor'] = False
  
          glActiveTexture(GL_TEXTURE0)
          glBindTexture(self.texture.target, self.texture.id)
  
          glEnable(GL_BLEND)
          glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
  
      def unset_state(self):
          glDisable(GL_BLEND)
          glBindTexture(self.texture.target, 0)
          self.program.stop()
  
      def __repr__(self):
          return "{0}({1})".format(self.__class__.__name__, self.texture)
  
      def __eq__(self, other):
          return (other.__class__ is self.__class__ and
                  self.program.id is other.program.id and
                  self.order == other.order and
                  self.texture.target == other.texture.target and
                  self.texture.id == other.texture.id)
  
      def __hash__(self):
          return hash((self.program.id, self.order, self.texture.target, self.texture.id))
  
  
  class ScrollableTextLayoutGroup(graphics.Group):
  
      scissor_area = 0, 0, 0, 0
  
      def __init__(self, texture, order=1, program=None):
          """Default rendering group for :py:class:`~pyglet.text.layout.ScrollableTextLayout`.
  
          The group maintains internal state for specifying the viewable
          area, and for scrolling. Because the group has internal state
          specific to the text layout, the group is never shared.
          """
          super().__init__(order=order)
          self.texture = texture
          self.program = program or get_default_layout_shader()
  
      def set_state(self):
          self.program.use()
          self.program['scissor'] = True
          self.program['scissor_area'] = self.scissor_area
  
          glActiveTexture(GL_TEXTURE0)
          glBindTexture(self.texture.target, self.texture.id)
  
          glEnable(GL_BLEND)
          glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
  
      def unset_state(self):
          glDisable(GL_BLEND)
          glBindTexture(self.texture.target, 0)
          self.program.stop()
  
      def __repr__(self):
          return f"{self.__class__.__name__}({self.texture})"
  
      def __eq__(self, other):
          return self is other
  
      def __hash__(self):
          return id(self)
  
  
  class IncrementalTextLayoutGroup(ScrollableTextLayoutGroup):
      # Subclass so that the scissor_area isn't shared with the
      # ScrollableTextLayout. We use a class variable here so
      # that it can be set before the document glyphs are created.
      scissor_area = 0, 0, 0, 0
  
  
  class TextDecorationGroup(graphics.Group):
      def __init__(self, order=0, program=None):
          """Create a text decoration rendering group.
  
          The group is created internally when a :py:class:`~pyglet.text.Label`
          is created; applications usually do not need to explicitly create it.
          """
          super().__init__(order=order)
          self.program = program or get_default_decoration_shader()
  
      def set_state(self):
          self.program.use()
          self.program['scissor'] = False
  
          glEnable(GL_BLEND)
          glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
  
      def unset_state(self):
          glDisable(GL_BLEND)
          self.program.stop()
  
  
  class ScrollableTextDecorationGroup(graphics.Group):
  
      scissor_area = 0, 0, 0, 0
  
      def __init__(self, order=0, program=None):
          """Create a text decoration rendering group.
  
          The group is created internally when a :py:class:`~pyglet.text.Label`
          is created; applications usually do not need to explicitly create it.
          """
          super().__init__(order=order)
          self.program = program or get_default_decoration_shader()
  
      def set_state(self):
          self.program.use()
          self.program['scissor'] = True
          self.program['scissor_area'] = self.scissor_area
  
          glEnable(GL_BLEND)
          glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
  
      def unset_state(self):
          glDisable(GL_BLEND)
          self.program.stop()
  
  
  class IncrementalTextDecorationGroup(ScrollableTextDecorationGroup):
      # Subclass so that the scissor_area isn't shared with the
      # ScrollableTextDecorationGroup. We use a class variable here so
      # that it can be set before the document glyphs are created.
      scissor_area = 0, 0, 0, 0
  
  
  # ####################
  
  
  class TextLayout:
      """Lay out and display documents.
  
      This class is intended for displaying documents that do not change
      regularly -- any change will cost some time to lay out the complete
      document again and regenerate all vertex lists.
  
      The benefit of this class is that texture state is shared between
      all layouts of this class.  The time to draw one :py:func:`~pyglet.text.layout.TextLayout` may be
      roughly the same as the time to draw one :py:class:`~pyglet.text.layout.IncrementalTextLayout`; but
      drawing ten :py:func:`~pyglet.text.layout.TextLayout` objects in one batch is much faster than drawing
      ten incremental or scrollable text layouts.
  
      :py:func:`~pyglet.text.Label` and :py:func:`~pyglet.text.HTMLLabel` provide a convenient interface to this class.
  
      :Ivariables:
          `content_width` : int
              Calculated width of the text in the layout.  This may overflow
              the desired width if word-wrapping failed.
          `content_height` : int
              Calculated height of the text in the layout.
          `default_group_class` : `~pyglet.graphics.Group`
              Top-level rendering group.
          `background_decoration_group` : `~pyglet.graphics.Group`
              Rendering group for background color.
          `foreground_decoration_group` : `~pyglet.graphics.Group`
              Rendering group for glyph underlines.
  
      """
      _document = None
      _vertex_lists = []
      _boxes = []
  
      _update_enabled = True
      _own_batch = False
      default_group_class = TextLayoutGroup
  
      _x = 0
      _y = 0
      _width = None
      _height = None
      _anchor_x = 'left'
      _anchor_y = 'bottom'
      _content_valign = 'top'
      _multiline = False
  
      def __init__(self, document, width=None, height=None,
                   multiline=False, dpi=None, batch=None, group=None,
                   wrap_lines=True):
          """Create a text layout.
  
          :Parameters:
              `document` : `AbstractDocument`
                  Document to display.
              `width` : int
                  Width of the layout in pixels, or None
              `height` : int
                  Height of the layout in pixels, or None
              `multiline` : bool
                  If False, newline and paragraph characters are ignored, and
                  text is not word-wrapped.
                  If True, text is wrapped only if the `wrap_lines` is True.
              `dpi` : float
                  Font resolution; defaults to 96.
              `batch` : `~pyglet.graphics.Batch`
                  Optional graphics batch to add this layout to.
              `group` : `~pyglet.graphics.Group`
                  Optional Group to parent all internal Groups that this text
                  layout uses.  Note that layouts with the same Groups will
                  be rendered simultaneously in a Batch.
              `wrap_lines` : bool
                  If True and `multiline` is True, the text is word-wrapped using
                  the specified width.
  
          """
          self.content_width = 0
          self.content_height = 0
  
          self._group = group
  
          self.background_decoration_group = TextDecorationGroup(order=0)
          self.foreground_decoration_group = TextDecorationGroup(order=2)
  
          self.groups = {}
  
          if batch is None:
              batch = graphics.Batch()
              self._own_batch = True
          self._batch = batch
  
          self._width = width
          self._height = height
          self._multiline = multiline
  
          # Alias the correct flow method:
          self._flow_glyphs = self._flow_glyphs_wrap if multiline else self._flow_glyphs_single_line
  
          self._wrap_lines_flag = wrap_lines
          self._wrap_lines_invariant()
  
          self._dpi = dpi or 96
          self.document = document
  
      @property
      def dpi(self):
          """Get DPI used by this layout.
  
          :type: float
          """
          return self._dpi
  
      @property
      def document(self):
          """Document to display.
  
           For :py:class:`~pyglet.text.layout.IncrementalTextLayout` it is
           far more efficient to modify a document in-place than to replace
           the document instance on the layout.
  
           :type: `AbstractDocument`
           """
          return self._document
  
      @document.setter
      def document(self, document):
          if self._document:
              self._document.remove_handlers(self)
              self._uninit_document()
          document.push_handlers(self)
          self._document = document
          self._init_document()
  
      @property
      def batch(self):
          """The Batch that this Layout is assigned to.
  
          If no Batch is assigned, an internal Batch is
          created and used.
  
          :type: :py:class:`~pyglet.graphics.Batch`
  
          """
          return self._batch
  
      @batch.setter
      def batch(self, batch):
          if self._batch == batch:
              return
  
          if batch is None:
              self._batch = graphics.Batch()
              self._own_batch = True
              self._update()
          elif batch is not None:
              self._batch = batch
              self._own_batch = False
              self._update()
  
      @property
      def x(self):
          """X coordinate of the layout.
  
          See also :py:attr:`~pyglet.text.layout.TextLayout.anchor_x`.
  
          :type: int
          """
          return self._x
  
      @x.setter
      def x(self, x):
          self._set_x(x)
  
      def _set_x(self, x):
          if self._boxes:
              self._x = x
              self._update()
          else:
              dx = x - self._x
              for vertex_list in self._vertex_lists:
                  vertices = vertex_list.vertices[:]
                  vertices[::2] = [x + dx for x in vertices[::2]]
                  vertex_list.vertices[:] = vertices
              self._x = x
  
      @property
      def y(self):
          """Y coordinate of the layout.
  
          See also `anchor_y`.
  
          :type: int
          """
          return self._y
  
      @y.setter
      def y(self, y):
          self._set_y(y)
  
      def _set_y(self, y):
          if self._boxes:
              self._y = y
              self._update()
          else:
              dy = y - self._y
              for vertex_list in self._vertex_lists:
                  vertices = vertex_list.vertices[:]
                  vertices[1::2] = [y + dy for y in vertices[1::2]]
                  vertex_list.vertices[:] = vertices
              self._y = y
  
      @property
      def position(self):
          """The (X, Y) coordinates of the layout, as a tuple.
  
          See also :py:attr:`~pyglet.text.layout.TextLayout.anchor_x`,
          and :py:attr:`~pyglet.text.layout.TextLayout.anchor_y`.
  
          :type: (int, int)
          """
          return self._x, self._y
  
      @position.setter
      def position(self, position):
          x, y = position
          self._set_x(x)
          self._set_y(y)
  
      @property
      def width(self):
          """Width of the layout.
  
          This property has no effect if `multiline` is False or `wrap_lines` is False.
  
          :type: int
          """
          return self._width
  
      @width.setter
      def width(self, width):
          self._width = width
          self._wrap_lines_invariant()
          self._update()
  
      @property
      def height(self):
          """Height of the layout.
  
          :type: int
          """
          return self._height
  
      @height.setter
      def height(self, height):
          self._height = height
          self._update()
  
      @property
      def multiline(self):
          """Set if multiline layout is enabled.
  
          If multiline is False, newline and paragraph characters are ignored and
          text is not word-wrapped.
          If True, the text is word-wrapped only if the `wrap_lines` is True.
  
          :type: bool
          """
          return self._multiline
  
      @multiline.setter
      def multiline(self, multiline):
          self._multiline = multiline
          self._wrap_lines_invariant()
          self._update()
  
      @property
      def anchor_x(self):
          """Horizontal anchor alignment.
  
          This property determines the meaning of the `x` coordinate.
          It is one of the enumerants:
  
          ``"left"`` (default)
              The X coordinate gives the position of the left edge of the layout.
          ``"center"``
              The X coordinate gives the position of the center of the layout.
          ``"right"``
              The X coordinate gives the position of the right edge of the layout.
  
          For the purposes of calculating the position resulting from this
          alignment, the width of the layout is taken to be `width` if `multiline`
          is True and `wrap_lines` is True, otherwise `content_width`.
  
          :type: str
          """
          return self._anchor_x
  
      @anchor_x.setter
      def anchor_x(self, anchor_x):
          self._anchor_x = anchor_x
          self._update()
  
      @property
      def anchor_y(self):
          """Vertical anchor alignment.
  
          This property determines the meaning of the `y` coordinate.
          It is one of the enumerants:
  
          ``"top"``
              The Y coordinate gives the position of the top edge of the layout.
          ``"center"``
              The Y coordinate gives the position of the center of the layout.
          ``"baseline"``
              The Y coordinate gives the position of the baseline of the first
              line of text in the layout.
          ``"bottom"`` (default)
              The Y coordinate gives the position of the bottom edge of the layout.
  
          For the purposes of calculating the position resulting from this
          alignment, the height of the layout is taken to be the smaller of
          `height` and `content_height`.
  
          See also `content_valign`.
  
          :type: str
          """
          return self._anchor_y
  
      @anchor_y.setter
      def anchor_y(self, anchor_y):
          self._anchor_y = anchor_y
          self._update()
  
      @property
      def content_valign(self):
          """Vertical alignment of content within larger layout box.
  
          This property determines how content is positioned within the layout
          box when ``content_height`` is less than ``height``.  It is one
          of the enumerants:
  
          ``top`` (default)
              Content is aligned to the top of the layout box.
          ``center``
              Content is centered vertically within the layout box.
          ``bottom``
              Content is aligned to the bottom of the layout box.
  
          This property has no effect when ``content_height`` is greater
          than ``height`` (in which case the content is aligned to the top) or when
          ``height`` is ``None`` (in which case there is no vertical layout box
          dimension).
  
          :type: str
          """
          return self._content_valign
  
      @content_valign.setter
      def content_valign(self, content_valign):
          self._content_valign = content_valign
          self._update()
  
      def _wrap_lines_invariant(self):
          self._wrap_lines = self._multiline and self._wrap_lines_flag
          assert not self._wrap_lines or self._width,\
              "When the parameters 'multiline' and 'wrap_lines' are True, the parameter 'width' must be a number."
  
      def parse_distance(self, distance):
          if distance is None:
              return None
          return _parse_distance(distance, self._dpi)
  
      def begin_update(self):
          """Indicate that a number of changes to the layout or document
          are about to occur.
  
          Changes to the layout or document between calls to `begin_update` and
          `end_update` do not trigger any costly relayout of text.  Relayout of
          all changes is performed when `end_update` is called.
  
          Note that between the `begin_update` and `end_update` calls, values
          such as `content_width` and `content_height` are undefined (i.e., they
          may or may not be updated to reflect the latest changes).
          """
          self._update_enabled = False
  
      def end_update(self):
          """Perform pending layout changes since `begin_update`.
  
          See `begin_update`.
          """
          self._update_enabled = True
          self._update()
  
      def delete(self):
          """Remove this layout from its batch.
          """
          for vertex_list in self._vertex_lists:
              vertex_list.delete()
          self._vertex_lists.clear()
  
          for box in self._boxes:
              box.delete(self)
          self._boxes.clear()
  
      def draw(self):
          """Draw this text layout.
  
          Note that this method performs very badly if a batch was supplied to
          the constructor.  If you add this layout to a batch, you should
          ideally use only the batch's draw method.
          """
          if self._own_batch:
              self._batch.draw()
          else:
              self._batch.draw_subset(self._vertex_lists)
  
      def _get_lines(self):
          len_text = len(self._document.text)
          glyphs = self._get_glyphs()
          owner_runs = runlist.RunList(len_text, None)
          self._get_owner_runs(owner_runs, glyphs, 0, len_text)
          lines = [line for line in self._flow_glyphs(glyphs, owner_runs, 0, len_text)]
          self.content_width = 0
          self._flow_lines(lines, 0, len(lines))
          return lines
  
      def _update(self):
          if not self._update_enabled:
              return
  
          for _vertex_list in self._vertex_lists:
              _vertex_list.delete()
          for box in self._boxes:
              box.delete(self)
          self._vertex_lists = []
          self._boxes = []
          self.groups.clear()
  
          if not self._document or not self._document.text:
              return
  
          lines = self._get_lines()
  
          colors_iter = self._document.get_style_runs('color')
          background_iter = self._document.get_style_runs('background_color')
  
          left = self._get_left()
          top = self._get_top(lines)
  
          context = _StaticLayoutContext(self, self._document, colors_iter, background_iter)
          for line in lines:
              self._create_vertex_lists(left + line.x, top + line.y, line.start, line.boxes, context)
  
      def _update_color(self):
          colors_iter = self._document.get_style_runs('color')
          colors = []
          for start, end, color in colors_iter.ranges(0, colors_iter.end):
              if color is None:
                  color = (0, 0, 0, 255)
              colors.extend(color * ((end - start) * 4))
  
          start = 0
          for _vertex_list in self._vertex_lists:
              _vertex_list.colors = colors[start:start+len(_vertex_list.colors)]
              start += len(_vertex_list.colors)
  
      def _get_left(self):
          if self._multiline:
              width = self._width if self._wrap_lines else self.content_width
          else:
              width = self.content_width
  
          if self._anchor_x == 'left':
              return self._x
          elif self._anchor_x == 'center':
              return self._x - width // 2
          elif self._anchor_x == 'right':
              return self._x - width
          else:
              assert False, '`anchor_x` must be either "left", "center", or "right".'
  
      def _get_top(self, lines):
          if self._height is None:
              height = self.content_height
              offset = 0
          else:
              height = self._height
              if self._content_valign == 'top':
                  offset = 0
              elif self._content_valign == 'bottom':
                  offset = max(0, self._height - self.content_height)
              elif self._content_valign == 'center':
                  offset = max(0, self._height - self.content_height) // 2
              else:
                  assert False, '`content_valign` must be either "top", "bottom", or "center".'
  
          if self._anchor_y == 'top':
              return self._y - offset
          elif self._anchor_y == 'baseline':
              return self._y + lines[0].ascent - offset
          elif self._anchor_y == 'bottom':
              return self._y + height - offset
          elif self._anchor_y == 'center':
              if len(lines) == 1 and self._height is None:
                  # This "looks" more centered than considering all of the descent.
                  line = lines[0]
                  return self._y + line.ascent // 2 - line.descent // 4
              else:
                  return self._y + height // 2 - offset
          else:
              assert False, '`anchor_y` must be either "top", "bottom", "center", or "baseline".'
  
      def _get_bottom(self, lines):
          height = self._height or self.content_height
  
          if self._anchor_y == 'top':
              return self._y - height
          elif self._anchor_y == 'bottom':
              return self._y
          elif self._anchor_y == 'center':
              return self._y - height // 2
          elif self._anchor_y == 'baseline':
              return self._y - height + lines[0].ascent
          else:
              assert False, '`anchor_y` must be either "top", "bottom", "center", or "baseline".'
  
      def _init_document(self):
          self._update()
  
      def _uninit_document(self):
          pass
  
      def on_insert_text(self, start, text):
          """Event handler for `AbstractDocument.on_insert_text`.
  
          The event handler is bound by the text layout; there is no need for
          applications to interact with this method.
          """
          self._init_document()
  
      def on_delete_text(self, start, end):
          """Event handler for `AbstractDocument.on_delete_text`.
  
          The event handler is bound by the text layout; there is no need for
          applications to interact with this method.
          """
          self._init_document()
  
      def on_style_text(self, start, end, attributes):
          """Event handler for `AbstractDocument.on_style_text`.
  
          The event handler is bound by the text layout; there is no need for
          applications to interact with this method.
          """
          if len(attributes) == 1 and 'color' in attributes.keys():
              self._update_color()
          else:
              self._init_document()
  
      def _get_glyphs(self):
          glyphs = []
          runs = runlist.ZipRunIterator((
              self._document.get_font_runs(dpi=self._dpi),
              self._document.get_element_runs()))
          text = self._document.text
          for start, end, (font, element) in runs.ranges(0, len(text)):
              if element:
                  glyphs.append(_InlineElementBox(element))
              else:
                  glyphs.extend(font.get_glyphs(text[start:end]))
          return glyphs
  
      def _get_owner_runs(self, owner_runs, glyphs, start, end):
          owner = glyphs[start].owner
          run_start = start
          # TODO avoid glyph slice on non-incremental
          for i, glyph in enumerate(glyphs[start:end]):
              if owner != glyph.owner:
                  owner_runs.set_run(run_start, i + start, owner)
                  owner = glyph.owner
                  run_start = i + start
          owner_runs.set_run(run_start, end, owner)
  
      def _flow_glyphs_wrap(self, glyphs, owner_runs, start, end):
          """Word-wrap styled text into lines of fixed width.
  
          Fits `glyphs` in range `start` to `end` into `_Line` s which are
          then yielded.
          """
          owner_iterator = owner_runs.get_run_iterator().ranges(start, end)
  
          font_iterator = self._document.get_font_runs(dpi=self._dpi)
  
          align_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('align'),
                                                       lambda value: value in ('left', 'right', 'center'),
                                                       'left')
          if self._width is None:
              wrap_iterator = runlist.ConstRunIterator(len(self.document.text), False)
          else:
              wrap_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('wrap'),
                                                          lambda value: value in (True, False, 'char', 'word'),
                                                          True)
          margin_left_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('margin_left'),
                                                             lambda value: value is not None, 0)
          margin_right_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('margin_right'),
                                                              lambda value: value is not None, 0)
          indent_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('indent'),
                                                        lambda value: value is not None, 0)
          kerning_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('kerning'),
                                                         lambda value: value is not None, 0)
          tab_stops_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('tab_stops'),
                                                           lambda value: value is not None, [])
          line = _Line(start)
          line.align = align_iterator[start]
          line.margin_left = self.parse_distance(margin_left_iterator[start])
          line.margin_right = self.parse_distance(margin_right_iterator[start])
          if start == 0 or self.document.text[start - 1] in u'\n\u2029':
              line.paragraph_begin = True
              line.margin_left += self.parse_distance(indent_iterator[start])
          wrap = wrap_iterator[start]
          if self._wrap_lines:
              width = self._width - line.margin_left - line.margin_right
  
          # Current right-most x position in line being laid out.
          x = 0
  
          # Boxes accumulated but not yet committed to a line.
          run_accum = []
          run_accum_width = 0
  
          # Amount of whitespace accumulated at end of line
          eol_ws = 0
  
          # Iterate over glyph owners (texture states); these form GlyphBoxes,
          # but broken into lines.
          font = None
          for start, end, owner in owner_iterator:
              font = font_iterator[start]
  
              # Glyphs accumulated in this owner but not yet committed to a
              # line.
              owner_accum = []
              owner_accum_width = 0
  
              # Glyphs accumulated in this owner AND also committed to the
              # current line (some whitespace has followed all of the committed
              # glyphs).
              owner_accum_commit = []
              owner_accum_commit_width = 0
  
              # Ignore kerning of first glyph on each line
              nokern = True
  
              # Current glyph index
              index = start
  
              # Iterate over glyphs in this owner run.  `text` is the
              # corresponding character data for the glyph, and is used to find
              # whitespace and newlines.
              for (text, glyph) in zip(self.document.text[start:end], glyphs[start:end]):
                  if nokern:
                      kern = 0
                      nokern = False
                  else:
                      kern = self.parse_distance(kerning_iterator[index])
  
                  if wrap != 'char' and text in u'\u0020\u200b\t':
                      # Whitespace: commit pending runs to this line.
                      for run in run_accum:
                          line.add_box(run)
                      run_accum = []
                      run_accum_width = 0
  
                      if text == '\t':
                          # Fix up kern for this glyph to align to the next tab stop
                          for tab_stop in tab_stops_iterator[index]:
                              tab_stop = self.parse_distance(tab_stop)
                              if tab_stop > x + line.margin_left:
                                  break
                          else:
                              # No more tab stops, tab to 100 pixels
                              tab = 50.
                              tab_stop = (((x + line.margin_left) // tab) + 1) * tab
                          kern = int(tab_stop - x - line.margin_left - glyph.advance)
  
                      owner_accum.append((kern, glyph))
                      owner_accum_commit.extend(owner_accum)
                      owner_accum_commit_width += owner_accum_width + glyph.advance + kern
                      eol_ws += glyph.advance + kern
  
                      owner_accum = []
                      owner_accum_width = 0
  
                      x += glyph.advance + kern
                      index += 1
  
                      # The index at which the next line will begin (the
                      # current index, because this is the current best
                      # breakpoint).
                      next_start = index
                  else:
                      new_paragraph = text in u'\n\u2029'
                      new_line = (text == u'\u2028') or new_paragraph
                      if (wrap and self._wrap_lines and x + kern + glyph.advance >= width) or new_line:
                          # Either the pending runs have overflowed the allowed
                          # line width or a newline was encountered.  Either
                          # way, the current line must be flushed.
  
                          if new_line or wrap == 'char':
                              # Forced newline or char-level wrapping.  Commit
                              # everything pending without exception.
                              for run in run_accum:
                                  line.add_box(run)
                              run_accum = []
                              run_accum_width = 0
                              owner_accum_commit.extend(owner_accum)
                              owner_accum_commit_width += owner_accum_width
                              owner_accum = []
                              owner_accum_width = 0
  
                              line.length += 1
                              next_start = index
                              if new_line:
                                  next_start += 1
  
                          # Create the _GlyphBox for the committed glyphs in the
                          # current owner.
                          if owner_accum_commit:
                              line.add_box(_GlyphBox(owner, font, owner_accum_commit, owner_accum_commit_width))
                              owner_accum_commit = []
                              owner_accum_commit_width = 0
  
                          if new_line and not line.boxes:
                              # Empty line: give it the current font's default
                              # line-height.
                              line.ascent = font.ascent
                              line.descent = font.descent
  
                          # Flush the line, unless nothing got committed, in
                          # which case it's a really long string of glyphs
                          # without any breakpoints (in which case it will be
                          # flushed at the earliest breakpoint, not before
                          # something is committed).
                          if line.boxes or new_line:
                              # Trim line width of whitespace on right-side.
                              line.width -= eol_ws
                              if new_paragraph:
                                  line.paragraph_end = True
                              yield line
                              try:
                                  line = _Line(next_start)
                                  line.align = align_iterator[next_start]
                                  line.margin_left = self.parse_distance(margin_left_iterator[next_start])
                                  line.margin_right = self.parse_distance(margin_right_iterator[next_start])
                              except IndexError:
                                  # XXX This used to throw StopIteration in some cases, causing the
                                  # final part of this method not to be executed. Refactoring
                                  # required to fix this
                                  return
                              if new_paragraph:
                                  line.paragraph_begin = True
  
                              # Remove kern from first glyph of line
                              if run_accum and hasattr(run_accum, 'glyphs') and run_accum.glyphs:
                                  k, g = run_accum[0].glyphs[0]
                                  run_accum[0].glyphs[0] = (0, g)
                                  run_accum_width -= k
                              elif owner_accum:
                                  k, g = owner_accum[0]
                                  owner_accum[0] = (0, g)
                                  owner_accum_width -= k
                              else:
                                  nokern = True
  
                              x = run_accum_width + owner_accum_width
                              if self._wrap_lines:
                                  width = self._width - line.margin_left - line.margin_right
  
                      if isinstance(glyph, _AbstractBox):
                          # Glyph is already in a box. XXX Ignore kern?
                          run_accum.append(glyph)
                          run_accum_width += glyph.advance
                          x += glyph.advance
                      elif new_paragraph:
                          # New paragraph started, update wrap style
                          wrap = wrap_iterator[next_start]
                          line.margin_left += self.parse_distance(indent_iterator[next_start])
                          if self._wrap_lines:
                              width = self._width - line.margin_left - line.margin_right
                      elif not new_line:
                          # If the glyph was any non-whitespace, non-newline
                          # character, add it to the pending run.
                          owner_accum.append((kern, glyph))
                          owner_accum_width += glyph.advance + kern
                          x += glyph.advance + kern
                      index += 1
                      eol_ws = 0
  
              # The owner run is finished; create GlyphBoxes for the committed
              # and pending glyphs.
              if owner_accum_commit:
                  line.add_box(_GlyphBox(owner, font, owner_accum_commit, owner_accum_commit_width))
              if owner_accum:
                  run_accum.append(_GlyphBox(owner, font, owner_accum, owner_accum_width))
                  run_accum_width += owner_accum_width
  
          # All glyphs have been processed: commit everything pending and flush
          # the final line.
          for run in run_accum:
              line.add_box(run)
  
          if not line.boxes:
              # Empty line gets font's line-height
              if font is None:
                  font = self._document.get_font(0, dpi=self._dpi)
              line.ascent = font.ascent
              line.descent = font.descent
  
          yield line
  
      def _flow_glyphs_single_line(self, glyphs, owner_runs, start, end):
          owner_iterator = owner_runs.get_run_iterator().ranges(start, end)
          font_iterator = self.document.get_font_runs(dpi=self._dpi)
          kern_iterator = runlist.FilteredRunIterator(self.document.get_style_runs('kerning'),
                                                      lambda value: value is not None, 0)
  
          line = _Line(start)
          font = font_iterator[0]
  
          if self._width:
              align_iterator = runlist.FilteredRunIterator(
                  self._document.get_style_runs('align'),
                  lambda value: value in ('left', 'right', 'center'),
                  'left')
              line.align = align_iterator[start]
  
          for start, end, owner in owner_iterator:
              font = font_iterator[start]
              width = 0
              owner_glyphs = []
              for kern_start, kern_end, kern in kern_iterator.ranges(start, end):
                  gs = glyphs[kern_start:kern_end]
                  width += sum([g.advance for g in gs])
                  width += kern * (kern_end - kern_start)
                  owner_glyphs.extend(zip([kern] * (kern_end - kern_start), gs))
              if owner is None:
                  # Assume glyphs are already boxes.
                  for kern, glyph in owner_glyphs:
                      line.add_box(glyph)
              else:
                  line.add_box(_GlyphBox(owner, font, owner_glyphs, width))
  
          if not line.boxes:
              line.ascent = font.ascent
              line.descent = font.descent
  
          line.paragraph_begin = line.paragraph_end = True
  
          yield line
  
      def _flow_lines(self, lines, start, end):
          margin_top_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('margin_top'),
                                                            lambda value: value is not None, 0)
          margin_bottom_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('margin_bottom'),
                                                               lambda value: value is not None, 0)
          line_spacing_iterator = self._document.get_style_runs('line_spacing')
          leading_iterator = runlist.FilteredRunIterator(self._document.get_style_runs('leading'),
                                                         lambda value: value is not None, 0)
  
          if start == 0:
              y = 0
          else:
              line = lines[start - 1]
              line_spacing = self.parse_distance(line_spacing_iterator[line.start])
              leading = self.parse_distance(leading_iterator[line.start])
  
              y = line.y
              if line_spacing is None:
                  y += line.descent
              if line.paragraph_end:
                  y -= self.parse_distance(margin_bottom_iterator[line.start])
  
          line_index = start
          for line in lines[start:]:
              if line.paragraph_begin:
                  y -= self.parse_distance(margin_top_iterator[line.start])
                  line_spacing = self.parse_distance(line_spacing_iterator[line.start])
                  leading = self.parse_distance(leading_iterator[line.start])
              else:
                  y -= leading
  
              if line_spacing is None:
                  y -= line.ascent
              else:
                  y -= line_spacing
              if line.align == 'left' or line.width > self.width:
                  line.x = line.margin_left
              elif line.align == 'center':
                  line.x = (self.width - line.margin_left - line.margin_right - line.width) // 2 + line.margin_left
              elif line.align == 'right':
                  line.x = self.width - line.margin_right - line.width
  
              self.content_width = max(self.content_width, line.width + line.margin_left)
  
              if line.y == y and line_index >= end:
                  # Early exit: all invalidated lines have been reflowed and the
                  # next line has no change (therefore subsequent lines do not
                  # need to be changed).
                  break
              line.y = y
  
              if line_spacing is None:
                  y += line.descent
              if line.paragraph_end:
                  y -= self.parse_distance(margin_bottom_iterator[line.start])
  
              line_index += 1
          else:
              self.content_height = -y
  
          return line_index
  
      def _create_vertex_lists(self, x, y, i, boxes, context):
          for box in boxes:
              box.place(self, i, x, y, context)
              x += box.advance
              i += box.length
  
  
  class ScrollableTextLayout(TextLayout):
      """Display text in a scrollable viewport.
  
      This class does not display a scrollbar or handle scroll events; it merely
      clips the text that would be drawn in :py:func:`~pyglet.text.layout.TextLayout`
      to the bounds of the layout given by `x`, `y`, `width` and `height`;
      and offsets the text by a scroll offset.
  
      Use `view_x` and `view_y` to scroll the text within the viewport.
      """
  
      default_group_class = ScrollableTextLayoutGroup
  
      _translate_x = 0
      _translate_y = 0
  
      def __init__(self, document, width, height, multiline=False, dpi=None, batch=None, group=None, wrap_lines=True):
          super().__init__(document, width, height, multiline, dpi, batch, group, wrap_lines)
          self._update_scissor_area()
  
      def _update_scissor_area(self):
          area = self._get_left(), self._get_bottom(self._get_lines()), self._width, self._height
          self.default_group_class.scissor_area = area
  
      # Properties
  
      @property
      def x(self):
          return self._x
  
      @x.setter
      def x(self, x):
          super()._set_x(x)
          self._update_scissor_area()
  
      @property
      def y(self):
          return self._y
  
      @y.setter
      def y(self, y):
          super()._set_y(y)
          self._update_scissor_area()
  
      @property
      def position(self):
          return self._x, self._y
  
      @position.setter
      def position(self, position):
          self.x, self.y = position
  
      @property
      def anchor_x(self):
          return self._anchor_x
  
      @anchor_x.setter
      def anchor_x(self, anchor_x):
          self._anchor_x = anchor_x
          super()._update()
          self._update_scissor_area()
  
      @property
      def anchor_y(self):
          return self._anchor_y
  
      @anchor_y.setter
      def anchor_y(self, anchor_y):
          self._anchor_y = anchor_y
          super()._update()
          self._update_scissor_area()
  
      # Offset of content within viewport
  
      def _update_translation(self):
          for _vertex_list in self._vertex_lists:
              _vertex_list.translation[:] = (-self._translate_x, -self._translate_y) * _vertex_list.count
  
      @property
      def view_x(self):
          """Horizontal scroll offset.
  
              The initial value is 0, and the left edge of the text will touch the left
              side of the layout bounds.  A positive value causes the text to "scroll"
              to the right.  Values are automatically clipped into the range
              ``[0, content_width - width]``
  
              :type: int
          """
          return self._translate_x
  
      @view_x.setter
      def view_x(self, view_x):
          self._translate_x = max(0, min(self.content_width - self._width, view_x))
          self._update_translation()
  
      @property
      def view_y(self):
          """Vertical scroll offset.
  
              The initial value is 0, and the top of the text will touch the top of the
              layout bounds (unless the content height is less than the layout height,
              in which case `content_valign` is used).
  
              A negative value causes the text to "scroll" upwards.  Values outside of
              the range ``[height - content_height, 0]`` are automatically clipped in
              range.
  
              :type: int
          """
          return self._translate_y
  
      @view_y.setter
      def view_y(self, view_y):
          # view_y must be negative.
          self._translate_y = min(0, max(self.height - self.content_height, view_y))
          self._update_translation()
  
  
  class IncrementalTextLayout(TextLayout, EventDispatcher):
      """Displayed text suitable for interactive editing and/or scrolling
      large documents.
  
      Unlike :py:func:`~pyglet.text.layout.TextLayout` and
      :py:class:`~pyglet.text.layout.ScrollableTextLayout`, this class generates
      vertex lists only for lines of text that are visible.  As the document is
      scrolled, vertex lists are deleted and created as appropriate to keep
      video memory usage to a minimum and improve rendering speed.
  
      Changes to the document are quickly reflected in this layout, as only the
      affected line(s) are reflowed.  Use `begin_update` and `end_update` to
      further reduce the amount of processing required.
  
      The layout can also display a text selection (text with a different
      background color).  The :py:class:`~pyglet.text.caret.Caret` class implements
      a visible text cursor and provides event handlers for scrolling, selecting and
      editing text in an incremental text layout.
      """
  
      _selection_start = 0
      _selection_end = 0
      _selection_color = [255, 255, 255, 255]
      _selection_background_color = [46, 106, 197, 255]
  
      default_group_class = IncrementalTextLayoutGroup
  
      _translate_x = 0
      _translate_y = 0
  
      def __init__(self, document, width, height, multiline=False, dpi=None, batch=None, group=None, wrap_lines=True):
  
          self.glyphs = []
          self.lines = []
  
          self.invalid_glyphs = _InvalidRange()
          self.invalid_flow = _InvalidRange()
          self.invalid_lines = _InvalidRange()
          self.invalid_style = _InvalidRange()
          self.invalid_vertex_lines = _InvalidRange()
          self.visible_lines = _InvalidRange()
  
          self.owner_runs = runlist.RunList(0, None)
  
          super().__init__(document, width, height, multiline, dpi, batch, group, wrap_lines)
  
          self._update_scissor_area()
          self._update_translation()
          self._update()
  
      def _update_scissor_area(self):
          area = self._get_left(), self._get_bottom(self._get_lines()), self._width, self._height
          self.default_group_class.scissor_area = area
  
      def _init_document(self):
          assert self._document, 'Cannot remove document from IncrementalTextLayout'
          self.on_insert_text(0, self._document.text)
  
      def _uninit_document(self):
          self.on_delete_text(0, len(self._document.text))
  
      def _get_lines(self):
          return self.lines
  
      def delete(self):
          for line in self.lines:
              line.delete(self)
          self._batch = None
          if self._document:
              self._document.remove_handlers(self)
          self._document = None
  
      def on_insert_text(self, start, text):
          len_text = len(text)
          self.glyphs[start:start] = [None] * len_text
  
          self.invalid_glyphs.insert(start, len_text)
          self.invalid_flow.insert(start, len_text)
          self.invalid_style.insert(start, len_text)
  
          self.owner_runs.insert(start, len_text)
  
          for line in self.lines:
              if line.start >= start:
                  line.start += len_text
  
          self._update()
  
      def on_delete_text(self, start, end):
          self.glyphs[start:end] = []
  
          self.invalid_glyphs.delete(start, end)
          self.invalid_flow.delete(start, end)
          self.invalid_style.delete(start, end)
  
          self.owner_runs.delete(start, end)
  
          size = end - start
          for line in self.lines:
              if line.start > start:
                  line.start = max(line.start - size, start)
  
          if start == 0:
              self.invalid_flow.invalidate(0, 1)
          else:
              self.invalid_flow.invalidate(start - 1, start)
  
          self._update()
  
      def on_style_text(self, start, end, attributes):
          if 'font_name' in attributes or 'font_size' in attributes or 'bold' in attributes or 'italic' in attributes:
              self.invalid_glyphs.invalidate(start, end)
          elif 'color' in attributes or 'background_color' in attributes:
              self.invalid_style.invalidate(start, end)
          else:  # Attributes that change flow
              self.invalid_flow.invalidate(start, end)
  
          self._update()
  
      def _update(self):
          if not self._update_enabled:
              return
  
          trigger_update_event = (self.invalid_glyphs.is_invalid() or
                                  self.invalid_flow.is_invalid() or
                                  self.invalid_lines.is_invalid())
  
          # Special care if there is no text:
          if not self.glyphs:
              for line in self.lines:
                  line.delete(self)
              del self.lines[:]
              self.lines.append(_Line(0))
              font = self.document.get_font(0, dpi=self._dpi)
              self.lines[0].ascent = font.ascent
              self.lines[0].descent = font.descent
              self.lines[0].paragraph_begin = self.lines[0].paragraph_end = True
              self.invalid_lines.invalidate(0, 1)
  
          self._update_glyphs()
          self._update_flow_glyphs()
          self._update_flow_lines()
          self._update_visible_lines()
          self._update_vertex_lists()
  
          # Reclamp view_y in case content height has changed and reset top of content.
          # self.view_y = self._translate_y
          # self._update_translation()
  
          if trigger_update_event:
              self.dispatch_event('on_layout_update')
  
      def _update_glyphs(self):
          invalid_start, invalid_end = self.invalid_glyphs.validate()
  
          if invalid_end - invalid_start <= 0:
              return
  
          # Find grapheme breaks and extend glyph range to encompass.
          text = self.document.text
          while invalid_start > 0:
              if grapheme_break(text[invalid_start - 1], text[invalid_start]):
                  break
              invalid_start -= 1
  
          len_text = len(text)
          while invalid_end < len_text:
              if grapheme_break(text[invalid_end - 1], text[invalid_end]):
                  break
              invalid_end += 1
  
          # Update glyphs
          runs = runlist.ZipRunIterator((
              self._document.get_font_runs(dpi=self._dpi),
              self._document.get_element_runs()))
          for start, end, (font, element) in runs.ranges(invalid_start, invalid_end):
              if element:
                  self.glyphs[start] = _InlineElementBox(element)
              else:
                  text = self.document.text[start:end]
                  self.glyphs[start:end] = font.get_glyphs(text)
  
          # Update owner runs
          self._get_owner_runs(self.owner_runs, self.glyphs, invalid_start, invalid_end)
  
          # Updated glyphs need flowing
          self.invalid_flow.invalidate(invalid_start, invalid_end)
  
      def _update_flow_glyphs(self):
          invalid_start, invalid_end = self.invalid_flow.validate()
  
          if invalid_end - invalid_start <= 0:
              return
  
          # Find first invalid line
          line_index = 0
          for i, line in enumerate(self.lines):
              if line.start >= invalid_start:
                  break
              line_index = i
  
          # Flow from previous line; fixes issue with adding a space into
          # overlong line (glyphs before space would then flow back onto
          # previous line).
          # TODO:  Could optimise this by keeping track of where the overlong lines are.
          line_index = max(0, line_index - 1)
  
          # (No need to find last invalid line; the update loop below stops
          # calling the flow generator when no more changes are necessary.)
  
          try:
              line = self.lines[line_index]
              invalid_start = min(invalid_start, line.start)
              line.delete(self)
              self.lines[line_index] = _Line(invalid_start)
              self.invalid_lines.invalidate(line_index, line_index + 1)
          except IndexError:
              line_index = 0
              invalid_start = 0
              line = _Line(0)
              self.lines.append(line)
              self.invalid_lines.insert(0, 1)
  
          content_width_invalid = False
          next_start = invalid_start
  
          for line in self._flow_glyphs(self.glyphs, self.owner_runs, invalid_start, len(self._document.text)):
              try:
                  old_line = self.lines[line_index]
                  old_line.delete(self)
                  old_line_width = old_line.width + old_line.margin_left
                  new_line_width = line.width + line.margin_left
                  if old_line_width == self.content_width and new_line_width < old_line_width:
                      content_width_invalid = True
                  self.lines[line_index] = line
                  self.invalid_lines.invalidate(line_index, line_index + 1)
              except IndexError:
                  self.lines.append(line)
                  self.invalid_lines.insert(line_index, 1)
  
              next_start = line.start + line.length
              line_index += 1
  
              try:
                  next_line = self.lines[line_index]
                  if next_start == next_line.start and next_start > invalid_end:
                      # No more lines need to be modified, early exit.
                      break
              except IndexError:
                  pass
          else:
              # The last line is at line_index - 1, if there are any more lines
              # after that they are stale and need to be deleted.
              if next_start == len(self._document.text) and line_index > 0:
                  for line in self.lines[line_index:]:
                      old_line_width = old_line.width + old_line.margin_left
                      if old_line_width == self.content_width:
                          content_width_invalid = True
                      line.delete(self)
                  del self.lines[line_index:]
  
          if content_width_invalid:
              # Rescan all lines to look for the new maximum content width
              content_width = 0
              for line in self.lines:
                  content_width = max(line.width + line.margin_left, content_width)
              self.content_width = content_width
  
      def _update_flow_lines(self):
          invalid_start, invalid_end = self.invalid_lines.validate()
          if invalid_end - invalid_start <= 0:
              return
  
          invalid_end = self._flow_lines(self.lines, invalid_start, invalid_end)
  
          # Invalidate lines that need new vertex lists.
          self.invalid_vertex_lines.invalidate(invalid_start, invalid_end)
  
      def _update_visible_lines(self):
          start = sys.maxsize
          end = 0
  
          for i, line in enumerate(self.lines):
              if line.y + line.descent < self._translate_y:
                  start = min(start, i)
              if line.y + line.ascent > self._translate_y - self.height:
                  end = max(end, i) + 1
  
          # print("Visible line start/end:", self.visible_lines.start, self.visible_lines.end)
  
          # Delete newly invisible lines
          for i in range(self.visible_lines.start, min(start, len(self.lines))):
              self.lines[i].delete(self)
          for i in range(end, min(self.visible_lines.end, len(self.lines))):
              self.lines[i].delete(self)
  
          # Invalidate newly visible lines
          self.invalid_vertex_lines.invalidate(start, self.visible_lines.start)
          self.invalid_vertex_lines.invalidate(self.visible_lines.end, end)
  
          self.visible_lines.start = start
          self.visible_lines.end = end
  
      def _update_vertex_lists(self):
          # Find lines that have been affected by style changes
          style_invalid_start, style_invalid_end = self.invalid_style.validate()
          self.invalid_vertex_lines.invalidate(
              self.get_line_from_position(style_invalid_start),
              self.get_line_from_position(style_invalid_end) + 1)
  
          invalid_start, invalid_end = self.invalid_vertex_lines.validate()
          if invalid_end - invalid_start <= 0:
              return
  
          colors_iter = self.document.get_style_runs('color')
          background_iter = self.document.get_style_runs('background_color')
          if self._selection_end - self._selection_start > 0:
              colors_iter = runlist.OverriddenRunIterator(
                  colors_iter,
                  self._selection_start,
                  self._selection_end,
                  self._selection_color)
              background_iter = runlist.OverriddenRunIterator(
                  background_iter,
                  self._selection_start,
                  self._selection_end,
                  self._selection_background_color)
  
          context = _IncrementalLayoutContext(self, self._document, colors_iter, background_iter)
  
          left = self._get_left()
          top = self._get_top(self.lines[invalid_start:invalid_end])
  
          for line in self.lines[invalid_start:invalid_end]:
              line.delete(self)
              context.line = line
              y = line.y
  
              # Early out if not visible
              if y + line.descent > self._translate_y:
                  continue
              elif y + line.ascent < self._translate_y - self.height:
                  break
  
              self._create_vertex_lists(left + line.x, top + y, line.start, line.boxes, context)
  
      @property
      def x(self):
          return self._x
  
      @x.setter
      def x(self, x):
          self._x = x
          self.on_insert_text(0, self._document.text)
          self._update()
  
      @property
      def y(self):
          return self._y
  
      @y.setter
      def y(self, y):
          self._y = y
          self.on_insert_text(0, self._document.text)
          self._update()
  
      @property
      def position(self):
          return self._x, self._y
  
      @position.setter
      def position(self, position):
          self.x, self.y = position
  
      @property
      def anchor_x(self):
          return self._anchor_x
  
      @anchor_x.setter
      def anchor_x(self, anchor_x):
          self._anchor_x = anchor_x
          self._update_scissor_area()
          self._update()
  
      @property
      def anchor_y(self):
          return self._anchor_y
  
      @anchor_y.setter
      def anchor_y(self, anchor_y):
          self._anchor_y = anchor_y
          self._update_scissor_area()
          self._update()
  
      @property
      def width(self):
          return self._width
  
      @width.setter
      def width(self, width):
          # Invalidate everything when width changes
          if width == self._width:
              return
          self._width = width
          self.invalid_flow.invalidate(0, len(self.document.text))
          self._update_scissor_area()
  
      @property
      def height(self):
          return self._height
  
      @height.setter
      def height(self, height):
          # Recalculate visible lines when height changes
          if height == self._height:
              return
          self._height = height
          if self._update_enabled:
              self._update_visible_lines()
              self._update_vertex_lists()
  
      @property
      def multiline(self):
          return self._multiline
  
      @multiline.setter
      def multiline(self, multiline):
          self.invalid_flow.invalidate(0, len(self.document.text))
          self._multiline = multiline
          self._wrap_lines_invariant()
          self._update()
  
      # Offset of content within viewport
  
      def _update_translation(self):
          for line in self.lines:
              for vlist in line.vertex_lists:
                  vlist.translation[:] = (-self._translate_x, -self._translate_y) * vlist.count
  
      @property
      def view_x(self):
          """Horizontal scroll offset.
  
          The initial value is 0, and the left edge of the text will touch the left
          side of the layout bounds.  A positive value causes the text to "scroll"
          to the right.  Values are automatically clipped into the range
          ``[0, content_width - width]``
  
          :type: int
          """
          return self._translate_x
  
      @view_x.setter
      def view_x(self, view_x):
          self._translate_x = max(0, min(self.content_width - self._width, view_x))
          self._update_translation()
  
      @property
      def view_y(self):
          """Vertical scroll offset.
  
          The initial value is 0, and the top of the text will touch the top of the
          layout bounds (unless the content height is less than the layout height,
          in which case `content_valign` is used).
  
          A negative value causes the text to "scroll" upwards.  Values outside of
          the range ``[height - content_height, 0]`` are automatically clipped in
          range.
  
          :type: int
          """
          return self._translate_y
  
      @view_y.setter
      def view_y(self, view_y):
          # Invalidate invisible/visible lines when y scrolls
          # view_y must be negative.
          self._translate_y = min(0, max(self.height - self.content_height, view_y))
          self._update_translation()
          self._update_visible_lines()
          self._update_vertex_lists()
  
      # Visible selection
  
      def set_selection(self, start, end):
          """Set the text selection range.
  
          If ``start`` equals ``end`` no selection will be visible.
  
          :Parameters:
              `start` : int
                  Starting character position of selection.
              `end` : int
                  End of selection, exclusive.
  
          """
          start = max(0, start)
          end = min(end, len(self.document.text))
          if start == self._selection_start and end == self._selection_end:
              return
  
          if end > self._selection_start and start < self._selection_end:
              # Overlapping, only invalidate difference
              self.invalid_style.invalidate(min(start, self._selection_start), max(start, self._selection_start))
              self.invalid_style.invalidate(min(end, self._selection_end), max(end, self._selection_end))
          else:
              # Non-overlapping, invalidate both ranges
              self.invalid_style.invalidate(self._selection_start, self._selection_end)
              self.invalid_style.invalidate(start, end)
  
          self._selection_start = start
          self._selection_end = end
  
          self._update()
  
      @property
      def selection_start(self):
          """Starting position of the active selection.
  
          :see: `set_selection`
  
          :type: int
          """
          return self._selection_start
  
      @selection_start.setter
      def selection_start(self, start):
          self.set_selection(start, self._selection_end)
  
      @property
      def selection_end(self):
          """End position of the active selection (exclusive).
  
          :see: `set_selection`
  
          :type: int
          """
          return self._selection_end
  
      @selection_end.setter
      def selection_end(self, end):
          self.set_selection(self._selection_start, end)
  
      @property
      def selection_color(self):
          """Text color of active selection.
  
          The color is an RGBA tuple with components in range [0, 255].
  
          :type: (int, int, int, int)
          """
          return self._selection_color
  
      @selection_color.setter
      def selection_color(self, color):
          self._selection_color = color
          self.invalid_style.invalidate(self._selection_start, self._selection_end)
  
      @property
      def selection_background_color(self):
          """Background color of active selection.
  
          The color is an RGBA tuple with components in range [0, 255].
  
          :type: (int, int, int, int)
          """
          return self._selection_background_color
  
      @selection_background_color.setter
      def selection_background_color(self, background_color):
          self._selection_background_color = background_color
          self.invalid_style.invalidate(self._selection_start, self._selection_end)
  
      # Coordinate translation
  
      def get_position_from_point(self, x, y):
          """Get the closest document position to a point.
  
          :Parameters:
              `x` : int
                  X coordinate
              `y` : int
                  Y coordinate
  
          """
          line = self.get_line_from_point(x, y)
          return self.get_position_on_line(line, x)
  
      def get_point_from_position(self, position, line=None):
          """Get the X, Y coordinates of a position in the document.
  
          The position that ends a line has an ambiguous point: it can be either
          the end of the line, or the beginning of the next line.  You may
          optionally specify a line index to disambiguate the case.
  
          The resulting Y coordinate gives the baseline of the line.
  
          :Parameters:
              `position` : int
                  Character position within document.
              `line` : int
                  Line index.
  
          :rtype: (int, int)
          :return: (x, y)
          """
          if line is None:
              line = self.lines[0]
              for next_line in self.lines:
                  if next_line.start > position:
                      break
                  line = next_line
          else:
              line = self.lines[line]
  
          x = line.x
  
          baseline = self._document.get_style('baseline', max(0, position - 1))
          if baseline is None:
              baseline = 0
          else:
              baseline = self.parse_distance(baseline)
  
          position -= line.start
          for box in line.boxes:
              if position - box.length <= 0:
                  x += box.get_point_in_box(position)
                  break
              position -= box.length
              x += box.advance
  
          return x + self._translate_x, line.y + self._translate_y + baseline
  
      def get_line_from_point(self, x, y):
          """Get the closest line index to a point.
  
          :Parameters:
              `x` : int
                  X coordinate.
              `y` : int
                  Y coordinate.
  
          :rtype: int
          """
          x -= self._translate_x
          y -= self._translate_y
  
          line_index = 0
          for line in self.lines:
              if y > line.y + line.descent:
                  break
              line_index += 1
          if line_index >= len(self.lines):
              line_index = len(self.lines) - 1
          return line_index
  
      def get_point_from_line(self, line):
          """Get the X, Y coordinates of a line index.
  
          :Parameters:
              `line` : int
                  Line index.
  
          :rtype: (int, int)
          :return: (x, y)
          """
          line = self.lines[line]
          return line.x + self._translate_x, line.y + self._translate_y
  
      def get_line_from_position(self, position):
          """Get the line index of a character position in the document.
  
          :Parameters:
              `position` : int
                  Document position.
  
          :rtype: int
          """
          line = -1
          for next_line in self.lines:
              if next_line.start > position:
                  break
              line += 1
          return line
  
      def get_position_from_line(self, line):
          """Get the first document character position of a given line index.
  
          :Parameters:
              `line` : int
                  Line index.
  
          :rtype: int
          """
          return self.lines[line].start + self._x
  
      def get_position_on_line(self, line, x):
          """Get the closest document position for a given line index and X
          coordinate.
  
          :Parameters:
              `line` : int
                  Line index.
              `x` : int
                  X coordinate.
  
          :rtype: int
          """
          line = self.lines[line]
          x -= self._x
  
          if x < line.x:
              return line.start
  
          position = line.start
          last_glyph_x = line.x
          for box in line.boxes:
              if 0 <= x - last_glyph_x < box.advance:
                  position += box.get_position_in_box(x - last_glyph_x)
                  break
              last_glyph_x += box.advance
              position += box.length
  
          return position
  
      def get_line_count(self):
          """Get the number of lines in the text layout.
  
          :rtype: int
          """
          return len(self.lines)
  
      def ensure_line_visible(self, line):
          """Adjust `view_y` so that the line with the given index is visible.
  
          :Parameters:
              `line` : int
                  Line index.
  
          """
          line = self.lines[line]
          y1 = line.y + line.ascent
          y2 = line.y + line.descent
          if y1 > self.view_y:
              self.view_y = y1
          elif y2 < self.view_y - self.height:
              self.view_y = y2 + self.height
  
      def ensure_x_visible(self, x):
          """Adjust `view_x` so that the given X coordinate is visible.
  
          The X coordinate is given relative to the current `view_x`.
  
          :Parameters:
              `x` : int
                  X coordinate
  
          """
          if x <= self.view_x + 10:
              self.view_x = x - 10
          elif x >= self.view_x + self.width:
              self.view_x = x - self.width + 10
          elif x >= self.view_x + self.width - 10 and self.content_width > self.width:
              self.view_x = x - self.width + 10
  
      if _is_pyglet_doc_run:
          def on_layout_update(self):
              """Some or all of the layout text was reflowed.
  
              Text reflow is caused by document edits or changes to the layout's
              size.  Changes to the layout's position or active selection, and
              certain document edits such as text color, do not cause a reflow.
  
              Handle this event to update the position of a graphical element
              that depends on the laid out position of a glyph or line.
  
              :event:
              """
  
  
  IncrementalTextLayout.register_event_type('on_layout_update')
  