Class: AsciinemaWin::ScreenBuffer

Inherits:
Object
  • Object
show all
Defined in:
lib/asciinema_win/screen_buffer.rb

Overview

Represents a captured screen buffer state with delta detection capabilities

This class captures the terminal screen buffer including:

  • Character content for each cell

  • Color/attribute information for each cell

  • Cursor position

  • Terminal dimensions

Examples:

Capture and compare screen states

buffer1 = ScreenBuffer.capture
# ... terminal content changes ...
buffer2 = ScreenBuffer.capture
diff = buffer2.diff(buffer1)
puts diff  # ANSI escape sequences to transform buffer1 to buffer2

Defined Under Namespace

Classes: Cell

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(width:, height:, cursor_x: 0, cursor_y: 0, timestamp: nil) ⇒ ScreenBuffer

Create a new ScreenBuffer with the given dimensions

Parameters:

  • width (Integer) —

    Screen width

  • height (Integer) —

    Screen height

  • cursor_x (Integer) (defaults to: 0) —

    Cursor X position

  • cursor_y (Integer) (defaults to: 0) —

    Cursor Y position

  • timestamp (Float, nil) (defaults to: nil) —

    Capture timestamp (defaults to current time)



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# File 'lib/asciinema_win/screen_buffer.rb', line 78

def initialize(width:, height:, cursor_x: 0, cursor_y: 0, timestamp: nil)
  @width = width
  @height = height
  @cursor_x = cursor_x
  @cursor_y = cursor_y
  @timestamp = timestamp || Process.clock_gettime(Process::CLOCK_MONOTONIC)
  @cells = Array.new(height) { Array.new(width) { empty_cell } }
end

Instance Attribute Details

#attributes ⇒ Integer (readonly)

Returns Windows console attribute value (raw).

Returns:

  • (Integer) —

    Windows console attribute value (raw)



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# File 'lib/asciinema_win/screen_buffer.rb', line 30

Cell = Data.define(:char, :foreground, :background, :attributes) do
  # @return [Boolean] True if cell is empty (space with default colors)
  def empty?
    (char == " " || char == "\0") && foreground == 7 && background == 0
  end

  # @return [Boolean] True if this cell equals another
  def ==(other)
    return false unless other.is_a?(Cell)

    char == other.char &&
      foreground == other.foreground &&
      background == other.background
  end

  alias eql? ==

  # @return [Integer] Hash code for this cell
  def hash
    [char, foreground, background].hash
  end
end

#background ⇒ Integer (readonly)

Returns Background color (ANSI color number 0-15 or 256-color/RGB).

Returns:

  • (Integer) —

    Background color (ANSI color number 0-15 or 256-color/RGB)



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# File 'lib/asciinema_win/screen_buffer.rb', line 30

Cell = Data.define(:char, :foreground, :background, :attributes) do
  # @return [Boolean] True if cell is empty (space with default colors)
  def empty?
    (char == " " || char == "\0") && foreground == 7 && background == 0
  end

  # @return [Boolean] True if this cell equals another
  def ==(other)
    return false unless other.is_a?(Cell)

    char == other.char &&
      foreground == other.foreground &&
      background == other.background
  end

  alias eql? ==

  # @return [Integer] Hash code for this cell
  def hash
    [char, foreground, background].hash
  end
end

#cells ⇒ Array<Array<Cell>> (readonly)

Returns 2D array of cells [row].

Returns:

  • (Array<Array<Cell>>) —

    2D array of cells [row]



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# File 'lib/asciinema_win/screen_buffer.rb', line 69

def cells
  @cells
end

#char ⇒ String (readonly)

Returns The character in this cell.

Returns:

  • (String) —

    The character in this cell



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# File 'lib/asciinema_win/screen_buffer.rb', line 30

Cell = Data.define(:char, :foreground, :background, :attributes) do
  # @return [Boolean] True if cell is empty (space with default colors)
  def empty?
    (char == " " || char == "\0") && foreground == 7 && background == 0
  end

  # @return [Boolean] True if this cell equals another
  def ==(other)
    return false unless other.is_a?(Cell)

    char == other.char &&
      foreground == other.foreground &&
      background == other.background
  end

  alias eql? ==

  # @return [Integer] Hash code for this cell
  def hash
    [char, foreground, background].hash
  end
end

#cursor_x ⇒ Integer (readonly)

Returns Cursor X position (0-indexed).

Returns:

  • (Integer) —

    Cursor X position (0-indexed)



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# File 'lib/asciinema_win/screen_buffer.rb', line 60

def cursor_x
  @cursor_x
end

#cursor_y ⇒ Integer (readonly)

Returns Cursor Y position (0-indexed).

Returns:

  • (Integer) —

    Cursor Y position (0-indexed)



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# File 'lib/asciinema_win/screen_buffer.rb', line 63

def cursor_y
  @cursor_y
end

#foreground ⇒ Integer (readonly)

Returns Foreground color (ANSI color number 0-15 or 256-color/RGB).

Returns:

  • (Integer) —

    Foreground color (ANSI color number 0-15 or 256-color/RGB)



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# File 'lib/asciinema_win/screen_buffer.rb', line 30

Cell = Data.define(:char, :foreground, :background, :attributes) do
  # @return [Boolean] True if cell is empty (space with default colors)
  def empty?
    (char == " " || char == "\0") && foreground == 7 && background == 0
  end

  # @return [Boolean] True if this cell equals another
  def ==(other)
    return false unless other.is_a?(Cell)

    char == other.char &&
      foreground == other.foreground &&
      background == other.background
  end

  alias eql? ==

  # @return [Integer] Hash code for this cell
  def hash
    [char, foreground, background].hash
  end
end

#height ⇒ Integer (readonly)

Returns Screen height in characters.

Returns:

  • (Integer) —

    Screen height in characters



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# File 'lib/asciinema_win/screen_buffer.rb', line 57

def height
  @height
end

#timestamp ⇒ Float (readonly)

Returns Timestamp when this buffer was captured (monotonic clock).

Returns:

  • (Float) —

    Timestamp when this buffer was captured (monotonic clock)



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# File 'lib/asciinema_win/screen_buffer.rb', line 66

def timestamp
  @timestamp
end

#width ⇒ Integer (readonly)

Returns Screen width in characters.

Returns:

  • (Integer) —

    Screen width in characters



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# File 'lib/asciinema_win/screen_buffer.rb', line 54

def width
  @width
end

Class Method Details

.capture ⇒ ScreenBuffer?

Capture the current screen buffer state from the Windows console

Returns:

  • (ScreenBuffer, nil) —

    Captured buffer or nil if capture fails

Raises:



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# File 'lib/asciinema_win/screen_buffer.rb', line 91

def self.capture
  unless Gem.win_platform?
    raise PlatformError, "Screen buffer capture requires Windows"
  end

  buffer_data = Win32Screen.capture
  return nil unless buffer_data

  from_win32_data(buffer_data)
end

.from_win32_data(data) ⇒ ScreenBuffer

Create a ScreenBuffer from Win32Screen capture data

Parameters:

  • data (Hash) —

    Data from Win32Screen.capture

Returns:



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# File 'lib/asciinema_win/screen_buffer.rb', line 106

def self.from_win32_data(data)
  buffer = new(
    width: data[:width],
    height: data[:height],
    cursor_x: data[:cursor_x],
    cursor_y: data[:cursor_y]
  )

  data[:lines].each_with_index do |line, row|
    chars = line[:chars]
    attributes = line[:attributes]

    chars.each_char.with_index do |char, col|
      break if col >= buffer.width

      attr = attributes[col] || 0
      fg, bg = parse_windows_attributes(attr)

      buffer.set_cell(row, col, Cell.new(
        char: char,
        foreground: fg,
        background: bg,
        attributes: attr
      ))
    end
  end

  buffer
end

.parse_windows_attributes(attributes) ⇒ Array<Integer, Integer>

Parse Windows console attributes into foreground and background colors

Parameters:

  • attributes (Integer) —

    Windows console attribute value

Returns:

  • (Array<Integer, Integer>) —
    foreground, background

    ANSI color numbers



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# File 'lib/asciinema_win/screen_buffer.rb', line 140

def self.parse_windows_attributes(attributes)
  # Extract foreground (bits 0-3)
  fg = attributes & 0x0F

  # Extract background (bits 4-7)
  bg = (attributes >> 4) & 0x0F

  [fg, bg]
end

Instance Method Details

#==(other) ⇒ Boolean Also known as: eql?

Check if this buffer equals another (content-wise)

Parameters:

Returns:

  • (Boolean) —

    True if buffers have identical content



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# File 'lib/asciinema_win/screen_buffer.rb', line 296

def ==(other)
  return false unless other.is_a?(ScreenBuffer)
  return false if @width != other.width || @height != other.height

  @cells.each_with_index do |row_cells, row|
    row_cells.each_with_index do |cell, col|
      return false unless cell == other.get_cell(row, col)
    end
  end

  true
end

#changed?(other) ⇒ Boolean

Check if buffer content has changed from another

Parameters:

Returns:

  • (Boolean) —

    True if any content differs



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# File 'lib/asciinema_win/screen_buffer.rb', line 320

def changed?(other)
  self != other
end

#diff(other = nil) ⇒ String

Compare this buffer with another and generate ANSI diff

Produces the minimal ANSI escape sequence needed to transform the other buffer’s display into this buffer’s display.

Parameters:

  • other (ScreenBuffer, nil) (defaults to: nil) —

    Previous buffer state (nil = empty screen)

Returns:

  • (String) —

    ANSI escape sequences to apply the changes



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# File 'lib/asciinema_win/screen_buffer.rb', line 180

def diff(other = nil)
  output = StringIO.new

  # If no previous buffer, render everything
  if other.nil?
    output << to_ansi
    return output.string
  end

  # Track what needs to be updated
  changes = []

  @height.times do |row|
    @width.times do |col|
      current = get_cell(row, col)
      previous = other.get_cell(row, col)

      # Only emit changes
      if current != previous
        changes << { row: row, col: col, cell: current }
      end
    end
  end

  # If more than 50% changed, just redraw the whole screen
  total_cells = @width * @height
  if changes.length > total_cells / 2
    output << "\e[H"  # Move to home
    output << to_ansi
    return output.string
  end

  # Apply incremental changes
  last_row = -1
  last_col = -1
  last_fg = nil
  last_bg = nil

  changes.each do |change|
    row = change[:row]
    col = change[:col]
    cell = change[:cell]

    # Move cursor if needed
    if row != last_row || col != last_col + 1
      output << "\e[#{row + 1};#{col + 1}H"
    end

    # Set colors if changed
    if cell.foreground != last_fg || cell.background != last_bg
      output << ansi_color_code(cell.foreground, cell.background)
      last_fg = cell.foreground
      last_bg = cell.background
    end

    output << cell.char

    last_row = row
    last_col = col
  end

  # Handle cursor position change
  if @cursor_x != other.cursor_x || @cursor_y != other.cursor_y
    output << "\e[#{@cursor_y + 1};#{@cursor_x + 1}H"
  end

  output.string
end

#get_cell(row, col) ⇒ Cell?

Get a cell at the given position

Parameters:

  • row (Integer) —

    Row index (0-indexed)

  • col (Integer) —

    Column index (0-indexed)

Returns:

  • (Cell, nil) —

    Cell at position or nil if out of bounds



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# File 'lib/asciinema_win/screen_buffer.rb', line 167

def get_cell(row, col)
  return nil if row < 0 || row >= @height || col < 0 || col >= @width

  @cells[row][col]
end

#hash ⇒ Integer

Returns Hash code for this buffer.

Returns:

  • (Integer) —

    Hash code for this buffer



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# File 'lib/asciinema_win/screen_buffer.rb', line 312

def hash
  [@width, @height, @cells].hash
end

#set_cell(row, col, cell) ⇒ void

This method returns an undefined value.

Set a cell at the given position

Parameters:

  • row (Integer) —

    Row index (0-indexed)

  • col (Integer) —

    Column index (0-indexed)

  • cell (Cell) —

    Cell to set



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# File 'lib/asciinema_win/screen_buffer.rb', line 156

def set_cell(row, col, cell)
  return if row < 0 || row >= @height || col < 0 || col >= @width

  @cells[row][col] = cell
end

#to_ansi ⇒ String

Convert entire buffer to ANSI escape sequence string

Returns:

  • (String) —

    Full ANSI representation of the screen buffer



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# File 'lib/asciinema_win/screen_buffer.rb', line 252

def to_ansi
  output = StringIO.new
  last_fg = nil
  last_bg = nil

  @cells.each_with_index do |row_cells, row|
    row_cells.each do |cell|
      # Set colors if changed
      if cell.foreground != last_fg || cell.background != last_bg
        output << "\e[0m" if last_fg || last_bg  # Reset first
        output << ansi_color_code(cell.foreground, cell.background)
        last_fg = cell.foreground
        last_bg = cell.background
      end

      output << cell.char
    end

    # Newline between rows (except last)
    if row < @height - 1
      output << "\e[0m" if last_fg || last_bg  # Reset before newline
      output << "\r\n"
      last_fg = nil
      last_bg = nil
    end
  end

  # Final reset
  output << "\e[0m"

  output.string
end

#to_text ⇒ String

Convert buffer to plain text (no color codes)

Returns:

  • (String) —

    Plain text content of the buffer



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# File 'lib/asciinema_win/screen_buffer.rb', line 288

def to_text
  @cells.map { |row| row.map(&:char).join.rstrip }.join("\n").rstrip
end