class BBS::TextBuffer

The text and the cursor of an input, without a screen: BBS::Field and BBS::Editor keep theirs in one and draw it each in their own way, so a key does the same in both.

The text is a list of lines; the cursor is a line index and a character position in that line.

buffer = BBS::TextBuffer.new('Hello', max: 80)
buffer.edit('!')        # => buffer
buffer.text             # => "Hello!"

Constants

KEYS: The editing keys besides the characters, and the method each calls.
MAX_LENGTH: The most characters a buffer holds when it is given no max: 64 KiB.
PRINTABLE_CHAR: One printable character, the only kind edit inserts (BBS::Text::PRINTABLE_CHAR).
SPACED_CONTROLS: The control characters of a new text that become a space: tab and CR.

Attributes

line [R]

The cursor’s line, an index into lines.

lines [R]

The lines of the text, without line ends (Array of String).

pos [R]

The cursor’s position in its line, 0 to the line’s length.

Public Class Methods

new (text = '', max: nil, single_line: false)

Source

# File lib/bbs/text_buffer.rb, line 40
def initialize(text = '', max: nil, single_line: false)
  @max    = max || MAX_LENGTH
  @single = single_line
  text    = text.to_s.gsub(Ansi::CRLF, "\n").tr(SPACED_CONTROLS, '  ')
  text    = text.tr("\n", ' ') if @single
  @lines  = text.split("\n", -1).map(&:dup)
  @lines  = [+''] if @lines.empty?
  @line   = @lines.size - 1
  @pos    = @lines.last.length
end

Creates a buffer holding text with the cursor at its end.

text: the text to start from; lines end with LF, tabs become spaces
max: the most characters the text may hold (line ends count as one); nil means MAX_LENGTH
single_line: one line: line ends in text become spaces and RETURN does not split the line

Public Instance Methods

edit (key)

Source

# File lib/bbs/text_buffer.rb, line 77
def edit(key)
  return nil unless editing?(key)

  key.is_a?(String) ? insert(key) : send(KEYS.fetch(key))
  self
end

Applies the editing key key (as BBS::Telnet#readkey returns it):

a one-character String: inserted at the cursor, unless the text is at max or it is not printable
:backspace: deletes before the cursor, joining the line to the one above at its start
:delete: deletes under the cursor, joining the next line at the end of this one
:left, :right: move one character, across line ends
:enter: splits the line at the cursor (not in a single-line buffer)

Returns self when the key was one of these, nil for any other key, which the caller handles.

length ()

Source

# File lib/bbs/text_buffer.rb, line 55
def length = @lines.sum(&:length) + @lines.size - 1

The number of characters in the text, line ends counted as one each.

place (line, pos)

Source

# File lib/bbs/text_buffer.rb, line 58
def place(line, pos)
  @line = line.clamp(0, @lines.size - 1)
  @pos  = pos.clamp(0, @lines[@line].length)
end

Puts the cursor on line at pos, both clamped to the text.

text ()

Source

# File lib/bbs/text_buffer.rb, line 52
def text = @lines.join("\n")

The text, the lines joined by LF.