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
DIM = 
8
SCROLLBACK_MAX = 
5000
OSC_MAX_LEN =

Cap on the OSC payload we buffer before parsing. URLs in OSC 8 can be long but rarely exceed a few hundred bytes; 4 KiB lets the parser stay tolerant of weird inputs without giving an attacker an unbounded sink.

4096
SYNC_TIMEOUT =

Inner programs (fzf ≥ 0.41, neovim, helix, …) bracket coherent screen updates with ‘e[?2026h … e[?2026l` (DECSET 2026 — “Synchronized Output”). When we see the open, we know more bytes are coming that belong to the same logical frame; rendering before the close shows a half-painted state. SYNC_TIMEOUT is the safety cap so a crashed inner program (which left ?2026h open) cannot wedge the pane indefinitely.

0.2

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 48

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 = +""
  @parser_osc = +""
  @feed_remainder = +"".b
  # Currently-active OSC 8 hyperlink body (the "8;params;URI" payload that
  # we'll wrap back around runs of cells when rendering), or nil when no
  # hyperlink is open. Interned via @hyperlink_intern so repeated identical
  # links share one frozen string for fast equality and small memory.
  @current_hyperlink = nil
  @hyperlink_intern = {}
  @dirty = true
  @scrollback = []
  @view_offset = 0
  @selection_anchor = nil
  @selection_cursor = nil
  @selection_mode = :linear
  @sync_pending = false
  @sync_started_at = nil
  @pending_replies = +"".b
end

Instance Attribute Details

#cols ⇒ Object (readonly)

Returns the value of attribute cols.



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# File 'lib/muxr/terminal.rb', line 46

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 46

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 46

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 46

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 113

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 46

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 198

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 115

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 207

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 409

def clear_dirty!
  @dirty = false
end

#clear_selection ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 347

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 405

def dirty?
  @dirty
end

#dump_text ⇒ Object

Return the currently-visible grid as a text string (rows joined by “n”, trailing whitespace stripped on each row). Used by the control surface to expose pane contents to programmatic clients (the MCP bridge in particular). This walks visible_cell so callers see whatever the user is currently looking at, including scrollback.



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# File 'lib/muxr/terminal.rb', line 124

def dump_text
  lines = Array.new(@rows) do |r|
    row = String.new(capacity: @cols)
    @cols.times { |c| row << visible_cell(r, c).char }
    row.rstrip
  end
  lines.join("\n")
end

#extract_selection_text ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 368

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 439

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 219

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 187

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 413

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 157

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 161

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 169

def scroll_to_bottom
  set_view_offset(0)
end

#scroll_to_top ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 165

def scroll_to_top
  set_view_offset(@scrollback.size)
end

#scrollback_size ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 149

def scrollback_size
  @scrollback.size
end

#scrolled_back? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/muxr/terminal.rb', line 153

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 354

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 181

def selection_active?
  !@selection_anchor.nil?
end

#selection_cursor_to(tr, tc) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 230

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 253

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

#selection_cursor_to_first_non_blank ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 257

def selection_cursor_to_first_non_blank
  return unless @selection_cursor
  tr = @selection_cursor[0]
  selection_cursor_to(tr, first_non_blank_col(tr))
end

#selection_cursor_to_line_end ⇒ Object 



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

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 239

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 249

def selection_cursor_to_top
  selection_cursor_to(0, 0)
end

#selection_cursor_to_viewport(where) ⇒ Object

Jump to top/middle/bottom of the visible viewport (vim H/M/L), landing on the first non-blank column of the destination line.



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# File 'lib/muxr/terminal.rb', line 265

def selection_cursor_to_viewport(where)
  return unless @selection_cursor
  vr = case where
       when :top    then 0
       when :middle then @rows / 2
       when :bottom then @rows - 1
       end
  return if vr.nil?
  tr = timeline_row_for_visible(vr).clamp(0, timeline_size - 1)
  selection_cursor_to(tr, first_non_blank_col(tr))
end

#selection_cursor_visible ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 360

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

#selection_cursor_word_backward(big: false) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 322

def selection_cursor_word_backward(big: false)
  return unless @selection_cursor
  tr, tc = @selection_cursor
  pos = step_backward(tr, tc)
  return unless pos
  tr, tc = pos
  while char_class_at(tr, tc, big: big) == :space
    pos = step_backward(tr, tc)
    unless pos
      selection_cursor_to(tr, tc)
      return
    end
    tr, tc = pos
  end
  cls = char_class_at(tr, tc, big: big)
  loop do
    pos = step_backward(tr, tc)
    if pos.nil? || pos[0] != tr || char_class_at(pos[0], pos[1], big: big) != cls
      selection_cursor_to(tr, tc)
      return
    end
    tr, tc = pos
  end
end

#selection_cursor_word_end(big: false) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 299

def selection_cursor_word_end(big: false)
  return unless @selection_cursor
  tr, tc = @selection_cursor
  pos = step_forward(tr, tc)
  return unless pos
  tr, tc = pos
  while char_class_at(tr, tc, big: big) == :space
    pos = step_forward(tr, tc)
    break unless pos
    tr, tc = pos
  end
  return if char_class_at(tr, tc, big: big) == :space
  cls = char_class_at(tr, tc, big: big)
  loop do
    pos = step_forward(tr, tc)
    if pos.nil? || pos[0] != tr || char_class_at(pos[0], pos[1], big: big) != cls
      selection_cursor_to(tr, tc)
      return
    end
    tr, tc = pos
  end
end

#selection_cursor_word_forward(big: false) ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 277

def selection_cursor_word_forward(big: false)
  return unless @selection_cursor
  tr, tc = @selection_cursor
  prev_cls = char_class_at(tr, tc, big: big)
  loop do
    nxt = step_forward(tr, tc)
    break unless nxt
    ntr, ntc = nxt
    cur_cls = char_class_at(ntr, ntc, big: big)
    # Row boundaries act as whitespace breaks even when the row is fully
    # packed (no trailing pad) — visually the user sees a new line.
    effective_prev = (ntr != tr) ? :space : prev_cls
    if effective_prev != cur_cls && cur_cls != :space
      selection_cursor_to(ntr, ntc)
      return
    end
    tr, tc = ntr, ntc
    prev_cls = cur_cls
  end
  selection_cursor_to(timeline_size - 1, @cols - 1)
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 214

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

#sync_deadline ⇒ Object 



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# File 'lib/muxr/terminal.rb', line 108

def sync_deadline
  return nil unless @sync_pending && @sync_started_at
  @sync_started_at + SYNC_TIMEOUT
end

#sync_pending? ⇒ Boolean

True iff the inner program has opened a synchronized-output block (e[?2026h) and not yet closed it, and the safety timeout has not elapsed. The Application uses this to defer rendering so the diff lands on a fully-formed frame instead of a half-painted one.

Returns:

  • (Boolean) 


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

def sync_pending?
  return false unless @sync_pending
  if @sync_started_at && (Process.clock_gettime(Process::CLOCK_MONOTONIC) - @sync_started_at) > SYNC_TIMEOUT
    @sync_pending = false
    @sync_started_at = nil
    return false
  end
  true
end

#take_pending_replies! ⇒ Object

Bytes the emulator owes back to the inner program in response to a query (currently DSR / Device Status Report — ‘e[5n` and `e[6n`). The Pane drains this after each feed and writes it to the PTY’s input side. Without it, programs like the AWS CLI fall back with a warning (“your terminal doesn’t support cursor position requests (CPR)”).



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# File 'lib/muxr/terminal.rb', line 87

def take_pending_replies!
  return nil if @pending_replies.empty?
  data = @pending_replies
  @pending_replies = +"".b
  data
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 137

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