class PrettyPrint

This is a convenience method which is same as follows:

begin
  q = PrettyPrint.new(output, maxwidth, newline, &genspace)
  ...
  q.flush
  output
end

# File lib/prettyprint.rb, line 43
def PrettyPrint.format(output='', maxwidth=79, newline="\n", genspace=lambda {|n| ' ' * n})
  q = PrettyPrint.new(output, maxwidth, newline, &genspace)
  yield q
  q.flush
  output
end

Creates a buffer for pretty printing.

output is an output target. If it is not specified, '' is assumed. It should have a << method which accepts the first argument obj of #text, the first argument sep of #breakable, the first argument newline of ::new, and the result of a given block for ::new.

maxwidth specifies maximum line length. If it is not specified, 79 is assumed. However actual outputs may overflow maxwidth if long non-breakable texts are provided.

newline is used for line breaks. “n” is used if it is not specified.

The block is used to generate spaces. {|width| ' ' * width} is used if it is not given.

# File lib/prettyprint.rb, line 80
def initialize(output='', maxwidth=79, newline="\n", &genspace)
  @output = output
  @maxwidth = maxwidth
  @newline = newline
  @genspace = genspace || lambda {|n| ' ' * n}

  @output_width = 0
  @buffer_width = 0
  @buffer = []

  root_group = Group.new(0)
  @group_stack = [root_group]
  @group_queue = GroupQueue.new(root_group)
  @indent = 0
end

This is similar to ::format but the result has no breaks.

maxwidth, newline and genspace are ignored.

The invocation of breakable in the block doesn't break a line and is treated as just an invocation of text.

# File lib/prettyprint.rb, line 57
def PrettyPrint.singleline_format(output='', maxwidth=nil, newline=nil, genspace=nil)
  q = SingleLine.new(output)
  yield q
  output
end

Breaks the buffer into lines that are shorter than maxwidth

# File lib/prettyprint.rb, line 180
def break_outmost_groups
  while @maxwidth < @output_width + @buffer_width
    return unless group = @group_queue.deq
    until group.breakables.empty?
      data = @buffer.shift
      @output_width = data.output(@output, @output_width)
      @buffer_width -= data.width
    end
    while !@buffer.empty? && Text === @buffer.first
      text = @buffer.shift
      @output_width = text.output(@output, @output_width)
      @buffer_width -= text.width
    end
  end
end

This says “you can break a line here if necessary”, and a width-column text sep is inserted if a line is not broken at the point.

If sep is not specified, “ ” is used.

If width is not specified, sep.length is used. You will have to specify this when sep is a multibyte character, for example.

# File lib/prettyprint.rb, line 244
def breakable(sep=' ', width=sep.length)
  group = @group_stack.last
  if group.break?
    flush
    @output << @newline
    @output << @genspace.call(@indent)
    @output_width = @indent
    @buffer_width = 0
  else
    @buffer << Breakable.new(sep, width, self)
    @buffer_width += width
    break_outmost_groups
  end
end

Returns the group most recently added to the stack.

Contrived example:

out = ""
=> ""
q = PrettyPrint.new(out)
=> #<PrettyPrint:0x82f85c0 @output="", @maxwidth=79, @newline="\n", @genspace=#<Proc:0x82f8368@/home/vbatts/.rvm/rubies/ruby-head/lib/ruby/2.0.0/prettyprint.rb:82 (lambda)>, @output_width=0, @buffer_width=0, @buffer=[], @group_stack=[#<PrettyPrint::Group:0x82f8138 @depth=0, @breakables=[], @break=false>], @group_queue=#<PrettyPrint::GroupQueue:0x82fb7c0 @queue=[[#<PrettyPrint::Group:0x82f8138 @depth=0, @breakables=[], @break=false>]]>, @indent=0>
q.group {
  q.text q.current_group.inspect
  q.text q.newline
  q.group(q.current_group.depth + 1) {
    q.text q.current_group.inspect
    q.text q.newline
    q.group(q.current_group.depth + 1) {
      q.text q.current_group.inspect
      q.text q.newline
      q.group(q.current_group.depth + 1) {
        q.text q.current_group.inspect
        q.text q.newline
      }
    }
  }
}
=> 284
 puts out
#<PrettyPrint::Group:0x8354758 @depth=1, @breakables=[], @break=false>
#<PrettyPrint::Group:0x8354550 @depth=2, @breakables=[], @break=false>
#<PrettyPrint::Group:0x83541cc @depth=3, @breakables=[], @break=false>
#<PrettyPrint::Group:0x8347e54 @depth=4, @breakables=[], @break=false>

# File lib/prettyprint.rb, line 153
def current_group
  @group_stack.last
end

This is similar to breakable except the decision to break or not is determined individually.

Two fill_breakable under a group may cause 4 results: (break,break), (break,non-break), (non-break,break), (non-break,non-break). This is different to breakable because two breakable under a group may cause 2 results: (break,break), (non-break,non-break).

The text sep is inserted if a line is not broken at this point.

If sep is not specified, “ ” is used.

If width is not specified, sep.length is used. You will have to specify this when sep is a multibyte character, for example.

# File lib/prettyprint.rb, line 232
def fill_breakable(sep=' ', width=sep.length)
  group { breakable sep, width }
end

first? is a predicate to test the call is a first call to first? with current group.

It is useful to format comma separated values as:

q.group(1, '[', ']') {
  xxx.each {|yyy|
    unless q.first?
      q.text ','
      q.breakable
    end
    ... pretty printing yyy ...
  }
}

first? is obsoleted in 1.8.2.

# File lib/prettyprint.rb, line 174
def first?
  warn "PrettyPrint#first? is obsoleted at 1.8.2."
  current_group.first?
end

outputs buffered data.

# File lib/prettyprint.rb, line 308
def flush
  @buffer.each {|data|
    @output_width = data.output(@output, @output_width)
  }
  @buffer.clear
  @buffer_width = 0
end

Groups line break hints added in the block. The line break hints are all to be used or not.

If indent is specified, the method call is regarded as nested by nest(indent) { … }.

If open_obj is specified, text open_obj, open_width is called before grouping. If close_obj is specified, text close_obj, close_width is called after grouping.

# File lib/prettyprint.rb, line 269
def group(indent=0, open_obj='', close_obj='', open_width=open_obj.length, close_width=close_obj.length)
  text open_obj, open_width
  group_sub {
    nest(indent) {
      yield
    }
  }
  text close_obj, close_width
end

Takes a block and queues a new group that is indented 1 level further.

# File lib/prettyprint.rb, line 280
def group_sub
  group = Group.new(@group_stack.last.depth + 1)
  @group_stack.push group
  @group_queue.enq group
  begin
    yield
  ensure
    @group_stack.pop
    if group.breakables.empty?
      @group_queue.delete group
    end
  end
end

Increases left margin after newline with indent for line breaks added in the block.

# File lib/prettyprint.rb, line 297
def nest(indent)
  @indent += indent
  begin
    yield
  ensure
    @indent -= indent
  end
end

This adds obj as a text of width columns in width.

If width is not specified, obj.length is used.

# File lib/prettyprint.rb, line 200
def text(obj, width=obj.length)
  if @buffer.empty?
    @output << obj
    @output_width += width
  else
    text = @buffer.last
    unless Text === text
      text = Text.new
      @buffer << text
    end
    text.add(obj, width)
    @buffer_width += width
    break_outmost_groups
  end
end