Class: TrickBag::Io::TextModeStatusUpdater

Inherits:
Object
  • Object
show all
Defined in:
lib/trick_bag/io/text_mode_status_updater.rb

Overview

Updates the terminal line with text, erasing the original content and displaying at the same place. Uses ANSI escape sequences for cursor positioning and clearing (see www.oldlinux.org/Linux.old/Ref-docs/ASCII/ANSI%20Escape%20Sequences.htm).

Example:

updater = TrickBag::Io::TextModeStatusUpdater.new(->{ Time.now }) 5.times { updater.print; sleep(1) }

Instance Method Summary collapse

Constructor Details

#initialize(text_generator, outstream = $stdout, force_output_non_tty = false) ⇒ TextModeStatusUpdater

Returns a new instance of TextModeStatusUpdater.



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# File 'lib/trick_bag/io/text_mode_status_updater.rb', line 15

def initialize(text_generator, outstream = $stdout, force_output_non_tty = false)
  @text_generator = text_generator
  @outstream = outstream
  @force_output_non_tty = force_output_non_tty
  @first_time = true
end

Instance Method Details

Causes the text generator lambda to be called, calls to_s on its result, and outputs the resulting text to the output stream, moving the cursor left to the beginning of the previous call’s output if not the first call to print.

Since this method uses ASCII escape sequences that would look messy in a file, this method will silently return if the output stream is not a TTY, unless

Parameters:

  • args —

    Optional arguments to be passed to the text generator



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# File 'lib/trick_bag/io/text_mode_status_updater.rb', line 32

def print(*args)

  # If output is being redirected, don't print anything; it will look like garbage;
  # But if output was forced (e.g. to write to a string), then allow it.
  return unless @outstream.tty? || @force_output_non_tty

  if @first_time
    @first_time = false
  else
    @outstream.print(move_cursor_left_text(@prev_text_length))
  end
  text = @text_generator.(*args).to_s
  @prev_text_length = text.length
  @outstream.print(clear_to_end_of_line_text + text)
end