Class: Muxr::Terminal

Inherits:
Object
  • Object
show all
Defined in:
lib/muxr/terminal.rb

Overview

A minimal VT100/ANSI terminal emulator. It maintains a fixed grid of cells plus a cursor and parser state. Bytes fed from a PTY are interpreted into mutations of the grid which the Renderer then composites into the final frame. The emulator implements enough of the protocol to host typical interactive shells (bash, zsh) and line-oriented programs.

Defined Under Namespace

Classes: Cell

Constant Summary collapse

BOLD = 
1
UNDERLINE = 
2
REVERSE = 
4
SCROLLBACK_MAX = 
5000

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(rows: 24, cols: 80) ⇒ Terminal

Returns a new instance of Terminal.



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# File 'lib/muxr/terminal.rb', line 32

def initialize(rows: 24, cols: 80)
  @rows = rows
  @cols = cols
  @buffer = Array.new(rows) { Array.new(cols) { blank_cell } }
  @cursor_row = 0
  @cursor_col = 0
  @saved_cursor = [0, 0]
  @fg = nil
  @bg = nil
  @attrs = 0
  @autowrap_pending = false
  @scroll_top = 0
  @scroll_bottom = rows - 1
  @parser_state = :ground
  @parser_params = +""
  @feed_remainder = +"".b
  @dirty = true
  @scrollback = []
  @view_offset = 0
  @selection_anchor = nil
  @selection_cursor = nil
  @selection_mode = :linear
end

Instance Attribute Details

#cols ⇒ Object (readonly)

Returns the value of attribute cols.



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# File 'lib/muxr/terminal.rb', line 30

def cols
  @cols
end

#cursor_col ⇒ Object (readonly)

Returns the value of attribute cursor_col.



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# File 'lib/muxr/terminal.rb', line 30

def cursor_col
  @cursor_col
end

#cursor_row ⇒ Object (readonly)

Returns the value of attribute cursor_row.



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# File 'lib/muxr/terminal.rb', line 30

def cursor_row
  @cursor_row
end

#rows ⇒ Object (readonly)

Returns the value of attribute rows.



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# File 'lib/muxr/terminal.rb', line 30

def rows
  @rows
end

#selection_mode ⇒ Object (readonly)

Returns the value of attribute selection_mode.



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# File 'lib/muxr/terminal.rb', line 56

def selection_mode
  @selection_mode
end

#view_offset ⇒ Object (readonly)

Returns the value of attribute view_offset.



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# File 'lib/muxr/terminal.rb', line 30

def view_offset
  @view_offset
end

Instance Method Details

#anchor_selection!(mode: :linear) ⇒ Object

Drop the anchor at the cursor’s current position. ‘mode` controls the selection shape: :linear (character-by-character, reading order) or :block (rectangular).



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# File 'lib/muxr/terminal.rb', line 127

def anchor_selection!(mode: :linear)
  return unless @selection_cursor
  @selection_anchor = @selection_cursor.dup
  @selection_mode = mode
  @dirty = true
end

#cell(r, c) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 58

def cell(r, c)
  @buffer[r][c]
end

#clear_anchor! ⇒ Object

Drop the anchor but keep the cursor so the user can continue navigating (vim’s behavior when pressing v while already in linear visual mode).



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# File 'lib/muxr/terminal.rb', line 136

def clear_anchor!
  return unless @selection_anchor
  @selection_anchor = nil
  @dirty = true
end

#clear_dirty! ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 248

def clear_dirty!
  @dirty = false
end

#clear_selection ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 186

def clear_selection
  return unless @selection_anchor
  @selection_anchor = nil
  @selection_cursor = nil
  @dirty = true
end

#dirty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/muxr/terminal.rb', line 244

def dirty?
  @dirty
end

#extract_selection_text ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 207

def extract_selection_text
  return "" unless @selection_anchor
  if @selection_mode == :block
    ar, ac = @selection_anchor
    br, bc = @selection_cursor
    min_r, max_r = ar <= br ? [ar, br] : [br, ar]
    min_c, max_c = ac <= bc ? [ac, bc] : [bc, ac]
    lines = []
    (min_r..max_r).each do |tr|
      row = timeline_row(tr)
      if row.nil? || min_c >= row.length
        lines << ""
        next
      end
      last = [max_c, row.length - 1].min
      chars = (min_c..last).map { |c| row[c]&.char || " " }
      lines << chars.join.rstrip
    end
    return lines.join("\n")
  end
  sr, sc, er, ec = ordered_selection
  lines = []
  (sr..er).each do |tr|
    row = timeline_row(tr)
    if row.nil?
      lines << ""
      next
    end
    first = (tr == sr) ? sc : 0
    last = (tr == er) ? ec : row.length - 1
    last = [last, row.length - 1].min
    chars = (first..last).map { |c| row[c]&.char || " " }
    lines << chars.join.rstrip
  end
  lines.join("\n")
end

#feed(data) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 278

def feed(data)
  bytes = @feed_remainder + data.b
  @feed_remainder = +"".b
  str = bytes.dup.force_encoding(Encoding::UTF_8)
  unless str.valid_encoding?
    # Find the longest valid UTF-8 prefix and stash the remainder for the
    # next feed call so multi-byte characters don't get garbled across PTY
    # read boundaries.
    raw = bytes.bytes
    while raw.any?
      candidate = raw.pack("C*").force_encoding(Encoding::UTF_8)
      break if candidate.valid_encoding?
      @feed_remainder = ([raw.last] + @feed_remainder.bytes).pack("C*").b
      raw.pop
    end
    str = raw.pack("C*").force_encoding(Encoding::UTF_8)
    # Bail out completely if we couldn't decode anything yet.
    return if str.empty?
  end
  str.each_char { |c| process_char(c) }
  @dirty = true
end

#move_selection_cursor_by(dr, dc) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 148

def move_selection_cursor_by(dr, dc)
  return unless @selection_cursor
  tr, tc = @selection_cursor
  ntr = (tr + dr).clamp(0, timeline_size - 1)
  ntc = (tc + dc).clamp(0, @cols - 1)
  return if ntr == tr && ntc == tc
  @selection_cursor = [ntr, ntc]
  ensure_selection_cursor_visible
  @dirty = true
end

#place_selection_cursor(r, c) ⇒ Object

Place the moving cursor at a viewport position without dropping an anchor — the user is still navigating, not yet selecting.



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# File 'lib/muxr/terminal.rb', line 116

def place_selection_cursor(r, c)
  tr = timeline_row_for_visible(r).clamp(0, timeline_size - 1)
  tc = c.clamp(0, @cols - 1)
  @selection_cursor = [tr, tc]
  @selection_anchor = nil
  @dirty = true
end

#resize(rows, cols) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 252

def resize(rows, cols)
  return if rows == @rows && cols == @cols
  new_buf = Array.new(rows) { Array.new(cols) { blank_cell } }
  keep_rows = [rows, @rows].min
  keep_cols = [cols, @cols].min
  src_start = @rows - keep_rows
  keep_rows.times do |i|
    keep_cols.times do |j|
      new_buf[i][j].copy_from(@buffer[src_start + i][j])
    end
  end
  @buffer = new_buf
  @rows = rows
  @cols = cols
  @scroll_top = 0
  @scroll_bottom = rows - 1
  @cursor_row = @cursor_row.clamp(0, rows - 1)
  @cursor_col = @cursor_col.clamp(0, cols - 1)
  @autowrap_pending = false
  # Selection points at timeline rows whose shape can't be remapped
  # meaningfully through a resize, so drop it rather than show a smear.
  @selection_anchor = nil
  @selection_cursor = nil
  @dirty = true
end

#scroll_back(n = 1) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 86

def scroll_back(n = 1)
  set_view_offset(@view_offset + n)
end

#scroll_forward(n = 1) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 90

def scroll_forward(n = 1)
  set_view_offset(@view_offset - n)
end

#scroll_to_bottom ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 98

def scroll_to_bottom
  set_view_offset(0)
end

#scroll_to_top ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 94

def scroll_to_top
  set_view_offset(@scrollback.size)
end

#scrollback_size ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 78

def scrollback_size
  @scrollback.size
end

#scrolled_back? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/muxr/terminal.rb', line 82

def scrolled_back?
  @view_offset > 0
end

#selected_at_visible?(r, c) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/muxr/terminal.rb', line 193

def selected_at_visible?(r, c)
  return false unless @selection_anchor
  tr = timeline_row_for_visible(r)
  inside_selection?(tr, c)
end

#selection_active? ⇒ Boolean

———- selection ———-

Selection coordinates are in the combined “timeline”:

0..scrollback.size-1                 → @scrollback rows
scrollback.size..scrollback.size+rows-1 → @buffer rows

so the selection stays anchored to the same text as the user pages through history.

Returns:

  • (Boolean) 


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# File 'lib/muxr/terminal.rb', line 110

def selection_active?
  !@selection_anchor.nil?
end

#selection_cursor_to(tr, tc) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 159

def selection_cursor_to(tr, tc)
  return unless @selection_cursor
  ntr = tr.clamp(0, timeline_size - 1)
  ntc = tc.clamp(0, @cols - 1)
  @selection_cursor = [ntr, ntc]
  ensure_selection_cursor_visible
  @dirty = true
end

#selection_cursor_to_bottom ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 182

def selection_cursor_to_bottom
  selection_cursor_to(timeline_size - 1, @cols - 1)
end

#selection_cursor_to_line_end ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 173

def selection_cursor_to_line_end
  return unless @selection_cursor
  selection_cursor_to(@selection_cursor[0], @cols - 1)
end

#selection_cursor_to_line_start ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 168

def selection_cursor_to_line_start
  return unless @selection_cursor
  selection_cursor_to(@selection_cursor[0], 0)
end

#selection_cursor_to_top ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 178

def selection_cursor_to_top
  selection_cursor_to(0, 0)
end

#selection_cursor_visible ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 199

def selection_cursor_visible
  return nil unless @selection_cursor
  tr, tc = @selection_cursor
  vr = tr - (@scrollback.size - @view_offset)
  return nil unless vr.between?(0, @rows - 1)
  [vr, tc]
end

#start_selection_at_visible(r, c, mode: :linear) ⇒ Object

Convenience for tests: place cursor at (r,c) AND anchor immediately.



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# File 'lib/muxr/terminal.rb', line 143

def start_selection_at_visible(r, c, mode: :linear)
  place_selection_cursor(r, c)
  anchor_selection!(mode: mode)
end

#visible_cell(r, c) ⇒ Object

Returns the Cell that should be visible at (r, c) given the current scrollback view_offset. When view_offset == 0 this is the live grid. When view_offset > 0, rows in the top of the visible area are sourced from @scrollback instead.



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# File 'lib/muxr/terminal.rb', line 66

def visible_cell(r, c)
  return @buffer[r][c] if @view_offset.zero?
  idx = @scrollback.size - @view_offset + r
  if idx < @scrollback.size
    row = @scrollback[idx]
    return blank_cell if row.nil? || c >= row.length
    row[c]
  else
    @buffer[idx - @scrollback.size][c]
  end
end