Version 0.4.0: mask, eine Eingabemaske mit eigener Oberfläche

CHANGELOG.md

@@ -7,7 +7,10 @@ folgen [Semantic Versioning](https://semver.org/lang/de/). Die Version steht in
 
 ## [Unveröffentlicht]
 
+## [0.4.0] - 2026-10-11
+
 ### Hinzugefügt
+- `mask`: Eingabemaske mit eigener Oberfläche (Felder mit Breite, Schaltflächen, Rahmen `-b`, `-s` zeigt das Bild ohne Terminal). Schreibt die Eingabe als Tabelle auf die Standardausgabe. Die Vorlage kommt wie bei `screen` von der Standardeingabe (`mask < entry`). Dazu `man/mask.man`, `demo/maskform` und Tests (auch mit Pseudo-Terminal).
 - `demo/entry`: beschriftete Eingabemaske für `screen` (README erklärt den Unterschied zu `form`).
 
 ## [0.3.0] - 2026-10-11

README.md

@@ -86,6 +86,22 @@ ein stiller Kommentar. Neue Befehle brauchen hier ein Beispiel, sonst schlägt d
   `CLEAR=$(clear.rdb) sh maske.sh > tabelle 2>&1`. Die Tabelle geht auf stderr (wie im Original),
   daher das `2>&1`. Mit `form` würde die Maske leer und doppelt aussehen.
 
+## Eingabemasken: `mask`
+
+`mask` ist die Variante von `screen` mit eigener Oberfläche (nur Ruby, kein ncurses). Es zeichnet die
+Vorlage (von der Standardeingabe, wie `screen`; ein Dateiname geht auch) selbst und schreibt die Eingabe als Tabelle auf die Standardausgabe, also pipefähig:
+
+```
+mask -b < demo/maskform                  Rahmen (-b), Felder, Schaltflächen
+mask < demo/maskform > neu               Tabelle in eine Datei
+mask < demo/maskform | append -h kunden  oder direkt in eine Tabelle
+mask -s < demo/maskform                  nur das Bild und die Feldpositionen, ohne Terminal
+```
+
+In der Vorlage: `<Spalte>` oder `<Spalte:20>` ist ein Feld (mit Breite), `[ Speichern ]` eine Schaltfläche,
+`[ Abbrechen ]` (oder Cancel, Abort, Quit) bricht ab, `<!date!>` fügt Befehlsausgabe ein. Kommt eine Spalte mehrfach
+vor, ist es ein Feld. Tab/Pfeile wechseln, Enter bestätigt, Esc bricht ab (Status 1, keine Ausgabe).
+
 ## Befehle
 
 | Gruppe | Befehle |
@@ -100,7 +116,7 @@ ein stiller Kommentar. Neue Befehle brauchen hier ein Beispiel, sonst schlägt d
 | Text | `cap` `uppercase` `lowercase` `substitute` `trimblank` `padstring` `length` `filesize` `ascii` `chr` `word` `prompt` `not` `path` |
 | Umwandeln | `tabletolist` `listtotable` `listtosh` `tabletofix` `fixtotable` `tabletostruct` `tabletotbl` `tabletofact` `tabletorule` `tabletom4` `tabletosed` `translate` `uniondict` |
 | Datum, Namen | `julian` `gregorian` `computedate` `todaysdate` `soundex` `like` `hashkey` |
-| Berichte | `report` `reportwriter` `screen` `label` `letter` |
+| Berichte | `report` `reportwriter` `screen` `mask` `label` `letter` |
 | Terminal, Hilfe | `termput` `tset` `clear.rdb` `cursor` `menu` `rdb` `commands` `helpme` `whatis` `whatwill` `howmany` `man` |
 | Betrieb | `testall` `testsearch` `timesearch` `rmcore` `cpdir.rdb` |
 | Buchhaltung (/act) | `act` `chartdup` `foot` `adjust` `balance` `close` `consolidate` `getjournal` `fillform` `calculate` `tax` `cashflow` `calcpay` `w2` `bom` `explode` `sale` `invoice` `cstate` `update.inv` |

bin/mask

@@ -0,0 +1 @@
+/home/wkh/Development/Coherent/rdb/bin/rdb

demo/entry

@@ -4,3 +4,6 @@ Name  : <Name>             Company: <Company>
 Street: <Street>
 City  : <City>             State  : <State>       ZIP: <ZIP>
 Phone : <Phone>
+
+[Speichern] [Abbrechen]
+

demo/maske.sh

@@ -0,0 +1,24 @@
+: paint crt screen
+exec 1>/dev/tty
+cat <<SCREEN
+${CLEAR}                  Mail List Entry Form
+
+Name  :                    Company:          
+Street:         
+City  :                    State  :               ZIP:      
+Phone :        
+SCREEN
+: read user input
+cursor  3  9 ; read Name;
+cursor  3 37 ; read Company;
+cursor  4  9 ; read Street;
+cursor  5  9 ; read City;
+cursor  5 37 ; read State;
+cursor  5 56 ; read ZIP;
+cursor  6  9 ; read Phone;
+: output table head
+exec 1>&2
+echo "Name	Company	Street	City	State	ZIP	Phone"
+echo "----	-------	------	----	-----	---	-----"
+: append row
+echo "$Name	$Company	$Street	$City	$State	$ZIP	$Phone"

demo/maskform

@@ -0,0 +1,9 @@
+Mail List Entry
+
+Name   : <Name:24>
+Company: <Company:24>
+Street : <Street:24>
+City   : <City:16>  State: <State:10>  ZIP: <ZIP:9>
+Phone  : <Phone:16>
+
+   [ Save ]   [ Cancel ]

demo/testall.cmds

@@ -187,6 +187,11 @@ letter form < maillist | head -5
 ## Run the script with: CLEAR=$(clear.rdb) sh script > table 2>&1   (the table goes to stderr)
 cat entry
 screen < entry
+## mask draws the form itself (fields, buttons, frame) and writes the row as a table on stdout.
+## It needs a terminal, so here only the picture of the form and its fields (-s) is shown.
+## Try it:  mask -b < maskform                  mask < maskform | append -h t
+cat maskform
+mask -s -b < maskform
 ## reportwriter: a sample report with page headings (the date is cut out)
 reportwriter -3 Prices < inventory | grep -v 'Report Date'
 ## tabletom4 / tabletosed / tabletostruct were shown above

demo/testall.old

@@ -745,6 +745,9 @@ Name  : <Name>             Company: <Company>
 Street: <Street>
 City  : <City>             State  : <State>       ZIP: <ZIP>
 Phone : <Phone>
+
+[Speichern] [Abbrechen]
+
 $ screen < entry
 : paint crt screen
 exec 1>/dev/tty
@@ -755,6 +758,8 @@ Name  :                    Company:
 Street:         
 City  :                    State  :               ZIP:      
 Phone :        
+
+[Speichern] [Abbrechen]
 SCREEN
 : read user input
 cursor  3  9 ; read Name;
@@ -770,6 +775,42 @@ echo "Name	Company	Street	City	State	ZIP	Phone"
 echo "----	-------	------	----	-----	---	-----"
 : append row
 echo "$Name	$Company	$Street	$City	$State	$ZIP	$Phone"
+## mask draws the form itself (fields, buttons, frame) and writes the row as a table on stdout.
+## It needs a terminal, so here only the picture of the form and its fields (-s) is shown.
+## Try it:  mask -b < maskform                  mask < maskform | append -h t
+$ cat maskform
+Mail List Entry
+
+Name   : <Name:24>
+Company: <Company:24>
+Street : <Street:24>
+City   : <City:16>  State: <State:10>  ZIP: <ZIP:9>
+Phone  : <Phone:16>
+
+   [ Save ]   [ Cancel ]
+$ mask -s -b < maskform
+┌──────────────────────────────────────────────────────────────┐
+│ Mail List Entry                                              │
+│                                                              │
+│ Name   : ________________________                            │
+│ Company: ________________________                            │
+│ Street : ________________________                            │
+│ City   : ________________  State: __________  ZIP: _________ │
+│ Phone  : ________________                                    │
+│                                                              │
+│    [ Save ]   [ Cancel ]                                     │
+└──────────────────────────────────────────────────────────────┘
+
+Fields:
+  Name	row 4 col 12 width 24
+  Company	row 5 col 12 width 24
+  Street	row 6 col 12 width 24
+  City	row 7 col 12 width 16
+  State	row 7 col 37 width 10
+  ZIP	row 7 col 54 width 9
+  Phone	row 8 col 12 width 16
+  [Save]	row 10 col 6
+  [Cancel]	row 10 col 17 (cancels)
 ## reportwriter: a sample report with page headings (the date is cut out)
 $ reportwriter -3 Prices < inventory | grep -v 'Report Date'
                      Prices
@@ -804,9 +845,9 @@ Item   Amount   Cost     Value     Description
 ## tabletom4 / tabletosed / tabletostruct were shown above
 ## ===== Help and the terminal =====
 $ rdb --version
-rdb 0.3.0
+rdb 0.4.0
 $ howmany
-134
+135
 $ whatis row
    row       - make a new table where rows match logical condition
    row       row 'column condition column-or-value ..' < table

lib/rdb/cmd/mask.rb

@@ -0,0 +1,275 @@
+# frozen_string_literal: true
+
+require 'io/console'
+require 'open3'
+
+# mask -- a full-screen input form.  It reads the same kind of form as `screen`
+# (text with <Column> fields) but draws it itself and writes the row typed in as
+# a table on the standard output, so it works in a pipe:  mask < entry | append t
+#
+# Besides <Column> the form may contain
+#   <Column:20>   a field 20 characters wide (otherwise as wide as the <...>)
+#   [ Save ]      a button; Cancel, Abort, Quit or Abbrechen cancel, any other accepts
+#   <!command!>   replaced by the first line of the command's output
+# Frames are plain text in the form, or drawn around everything with -b.
+module Rdb
+  module Mask
+    Slot = Struct.new(:row, :col, :width, :name)
+    Button = Struct.new(:row, :col, :text, :label)
+    CANCEL = /\A(cancel|abort|quit|abbrechen)\z/i
+    TOKEN = /<!(.*?)!>|<([^<>!:\n]+?)(?::(\d+))?>|\[ *([^\[\]<>\n]*[^\[\]<>\s]) *\]/
+
+    class Form
+      attr_reader :lines, :slots, :buttons
+
+      def self.parse(text, frame: false)
+        lines = []
+        slots = []
+        buttons = []
+        text.each_line(chomp: true).with_index do |line, row|
+          out = +''
+          pos = 0
+          while (m = TOKEN.match(line, pos))
+            out << line[pos...m.begin(0)]
+            if m[1]
+              out << Open3.capture2('sh', '-c', m[1]).first.lines.first.to_s.chomp
+            elsif m[2]
+              width = m[3] ? m[3].to_i : m[0].size
+              slots << Slot.new(row, out.size, width, m[2].strip)
+              out << ' ' * width
+            else
+              buttons << Button.new(row, out.size, m[0], m[4].strip)
+              out << m[0]
+            end
+            pos = m.end(0)
+          end
+          lines << (out << line[pos..].to_s)
+        end
+        new(lines, slots, buttons).then { |f| frame ? f.framed : f }
+      end
+
+      def initialize(lines, slots, buttons)
+        @lines = lines
+        @slots = slots
+        @buttons = buttons
+      end
+
+      def names
+        @slots.map(&:name).uniq
+      end
+
+      # Fields (first slot of each column) and buttons in reading order.
+      def items
+        fields = @slots.uniq(&:name).map { |s| [:field, s] }
+        (fields + @buttons.map { |b| [:button, b] }).sort_by { |_, o| [o.row, o.col] }
+      end
+
+      def framed
+        w = @lines.map(&:size).max.to_i
+        lines = ["┌#{'─' * (w + 2)}┐"] + @lines.map { |l| "│ #{l.ljust(w)} │" } + ["└#{'─' * (w + 2)}┘"]
+        self.class.new(lines,
+                       @slots.map { |s| Slot.new(s.row + 1, s.col + 2, s.width, s.name) },
+                       @buttons.map { |b| Button.new(b.row + 1, b.col + 2, b.text, b.label) })
+      end
+    end
+
+    # The state of one input session: values, which item has the focus, and the keys.
+    class Session
+      attr_reader :values, :focus, :pos
+
+      def initialize(form)
+        @form = form
+        @items = form.items
+        @values = form.names.to_h { |n| [n, +''] }
+        @focus = 0
+        reset_pos
+      end
+
+      def kind = @items[@focus]&.first
+
+      def current = @items[@focus]&.last
+
+      def field? = kind == :field
+
+      # Feed one key; returns :accept or :cancel when the session ends.
+      def feed(key)
+        case key
+        when "\t", "\e[B", "\e[6~" then move(1)
+        when "\e[Z", "\e[A", "\e[5~" then move(-1)
+        when "\r", "\n" then return enter
+        when "\x03", "\e", "\x04" then return :cancel
+        when "\e[C" then @pos = [@pos + 1, text.size].min if field?
+        when "\e[D" then @pos = [@pos - 1, 0].max if field?
+        when "\e[H", "\e[1~", "\eOH", "\x01" then @pos = 0
+        when "\e[F", "\e[4~", "\eOF", "\x05" then @pos = text.size if field?
+        when "\x7f", "\b" then backspace
+        when "\e[3~" then delete
+        when "\x15" then clear_field
+        when ' '
+          return press unless field?
+
+          insert(key)
+        else insert(key) if key.size == 1 && key.ord >= 32
+        end
+        nil
+      end
+
+      # Plain-text picture of the form (no escapes), for `mask -s` and the tests.
+      def plain
+        grid = @form.lines.map(&:dup)
+        @form.slots.each { |s| grid[s.row][s.col, s.width] = '_' * s.width }
+        grid.join("\n") + "\n"
+      end
+
+      # Escape sequences that paint the whole screen.
+      def render
+        out = +"\e[?25l\e[H\e[2J"
+        @form.lines.each_with_index { |l, r| out << "\e[#{r + 1};1H#{l}" }
+        cursor = nil
+        @form.slots.each do |s|
+          focused = field? && current.name == s.name
+          start = focused ? view_start(s.width) : 0
+          shown = @values[s.name][start, s.width].to_s.ljust(s.width)
+          out << "\e[#{s.row + 1};#{s.col + 1}H\e[#{focused ? 7 : 4}m#{shown}\e[0m"
+          cursor = [s.row + 1, s.col + 1 + @pos - start] if focused && current.equal?(s)
+        end
+        @form.buttons.each do |b|
+          focused = kind == :button && current.equal?(b)
+          out << "\e[#{b.row + 1};#{b.col + 1}H\e[#{focused ? 7 : 1}m#{b.text}\e[0m"
+          cursor = [b.row + 1, b.col + 1] if focused
+        end
+        out << "\e[#{cursor[0]};#{cursor[1]}H" if cursor
+        out << "\e[?25h" if field?
+        out
+      end
+
+      private
+
+      def text = field? ? @values[current.name] : +''
+
+      def reset_pos
+        @pos = field? ? text.size : 0
+      end
+
+      def move(delta)
+        @focus = (@focus + delta) % [@items.size, 1].max
+        reset_pos
+      end
+
+      def enter
+        return press unless field?
+
+        last = @focus == @items.size - 1
+        return :accept if last && @form.buttons.empty?
+
+        move(1)
+        nil
+      end
+
+      def press
+        current.label.match?(CANCEL) ? :cancel : :accept
+      end
+
+      def insert(key)
+        return unless field?
+
+        text.insert(@pos, key)
+        @pos += 1
+      end
+
+      def backspace
+        return unless field? && @pos.positive?
+
+        text.slice!(@pos - 1)
+        @pos -= 1
+      end
+
+      def delete
+        text.slice!(@pos) if field?
+      end
+
+      def clear_field
+        return unless field?
+
+        text.clear
+        @pos = 0
+      end
+
+      def view_start(width)
+        [@pos - width + 1, 0].max
+      end
+    end
+
+    def self.read_key(io)
+      c = io.getch
+      return c unless c == "\e" && io.wait_readable(0.05)
+
+      seq = +"\e#{io.getch}"
+      if seq == "\e["
+        loop do
+          c = io.getch
+          seq << c
+          break if c.ord.between?(0x40, 0x7e)
+        end
+      elsif seq == "\eO"
+        seq << io.getch
+      end
+      seq
+    end
+
+    # Run the form on a terminal; returns the values, or nil when cancelled.
+    def self.run(form, tty)
+      session = Session.new(form)
+      tty.raw do
+        tty.write "\e[?1049h"
+        begin
+          loop do
+            tty.write session.render
+            key = begin
+              read_key(tty)
+            rescue EOFError
+              "\x03"
+            end
+            result = session.feed(key)
+            return (result == :accept ? session.values : nil) if result
+          end
+        ensure
+          tty.write "\e[?25h\e[?1049l"
+        end
+      end
+    end
+  end
+end
+
+Rdb.register('mask', 'Full-screen input form that writes a table row', 'mask [-b] [-s] [form] < form > table') do |args|
+  frame = !args.delete('-b').nil?
+  show = !args.delete('-s').nil?
+  die 'usage: mask [-b] [-s] [form] < form > table' if args.size > 1
+  file = args.first
+  file.nil? || file == '-' || File.exist?(file) or die("#{file}: no such form")
+  text = file && file != '-' ? File.read(file) : $stdin.read
+  form = Rdb::Mask::Form.parse(text, frame: frame)
+  die "the form has no <field>" if form.names.empty?
+
+  session = Rdb::Mask::Session.new(form)
+  if show
+    print session.plain
+    puts '', 'Fields:'
+    form.slots.each { |s| puts "  #{s.name}\trow #{s.row + 1} col #{s.col + 1} width #{s.width}" }
+    form.buttons.each { |b| puts "  [#{b.label}]\trow #{b.row + 1} col #{b.col + 1}#{b.label.match?(Rdb::Mask::CANCEL) ? ' (cancels)' : ''}" }
+    next
+  end
+
+  tty = begin
+    File.open('/dev/tty', 'r+')
+  rescue SystemCallError
+    die 'no terminal available (mask draws on /dev/tty)'
+  end
+  values = Rdb::Mask.run(form, tty)
+  tty.close
+  if values.nil?
+    warn 'mask: cancelled'
+    exit 1
+  end
+  Rdb::Table.new(form.names, [form.names.map { |n| values[n].tr("\t\r\n", ' ') }]).write
+end

lib/rdb/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Rdb
-  VERSION = '0.3.0'
+  VERSION = '0.4.0'
 end

man/mask.man

@@ -0,0 +1,116 @@
+.TH mask "" "" "/rdb Command"
+.PC "Full-screen input form that writes a table row"
+\fBmask \fB[ -b ] [ -s ] [ \fIform\fB ] < \fIform \fB> \fItable\fR
+.PP
+.II "mask^input form"
+.II "form^full-screen input"
+.I "(Ruby re-creation only; the original /rdb has no such command.)"
+.PP
+The command
+.B mask
+draws
+.I form
+on the terminal, lets the user fill in its fields, and writes the result as
+a one-row table on the standard output.
+Unlike
+.BR screen ,
+it does not write a shell script: it runs the form itself.
+The screen is drawn on
+.BR /dev/tty ,
+so the table can be redirected or piped:
+.DM
+mask < maskform > newrow
+mask < maskform | append -h customer
+.DE
+.PP
+.I form
+is ordinary text.
+Everything is shown as it stands, except:
+.IP "\fB<Column>\fR" 1.2i
+An input field for column
+.IR Column .
+It is as wide as the text between the angle brackets, including the brackets.
+Blanks around the name are ignored, so \fB< City >\fR is column \fBCity\fR.
+.IP "\fB<Column:20>\fR"
+The same, but 20 characters wide.
+Longer input scrolls inside the field.
+.IP "\fB[ Save ]\fR"
+A button.
+A button whose label is
+.BR Cancel ,
+.BR Abort ,
+.B Quit
+or
+.B Abbrechen
+cancels; any other button accepts.
+.IP "\fB<!command!>\fR"
+Replaced by the first line the shell
+.I command
+writes.
+.PP
+If a column occurs more than once in the form, it is one field,
+and every place shows what was typed.
+The table has one column per field, in the order of first appearance.
+Frames are made of characters in the form, for example \fB+---+\fR or
+box-drawing characters.
+.SH Keys
+.nf
+Tab, Down, Enter     next field or button
+Shift-Tab, Up        previous field or button
+Left, Right, Home, End   move inside a field
+Backspace, Delete    erase; Ctrl-U clears the field
+Enter, Space         on a button: press it
+Enter                on the last field of a form without buttons: accept
+Esc, Ctrl-C          cancel
+.fi
+.PP
+When the user cancels,
+.B mask
+writes nothing and exits with status 1.
+.SH Options
+.IP \fB-b\fR 0.5i
+Draw a frame around the whole form.
+.IP \fB-s\fR
+Show the form as a plain picture (fields as underscores) with the position of
+each field and button, and exit.
+This needs no terminal and is useful to check a form.
+.PP
+Like
+.BR screen ,
+.B mask
+reads the form from the standard input.
+A file name argument is also accepted, and
+.B -
+means the standard input.
+.SH Example
+Form
+.BR maskform :
+.DM
+Mail List Entry
+
+Name   : <Name:24>
+City   : <City:16>  State: <State:10>
+ 
+   [ Save ]   [ Cancel ]
+.DE
+.PP
+.DM
+mask -b < maskform > newrow
+.DE
+.PP
+After typing ``Ann'' and ``Rome'', pressing Tab to the buttons and Enter on
+.BR Save ,
+.B newrow
+contains:
+.DM
+Name   City    State
+----   ----    -----
+Ann    Rome
+.DE
+.SH "See Also"
+.B
+cursor,
+report,
+screen
+.R
+.SO rdb

test/rdb_test.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 require_relative 'test_helper'
+require 'pty'
+require_relative '../lib/rdb'
 
 class SelectionTest < RdbCase
   def test_row_numeric_condition
@@ -523,3 +525,96 @@ class ActTest < RdbCase
     assert_equal [%w[b]], data(out)
   end
 end
+
+class MaskTest < RdbCase
+  def form(text, frame: false) = Rdb::Mask::Form.parse(text, frame: frame)
+
+  def type(session, *keys)
+    keys.each { |k| k.start_with?("\e") || k.size == 1 ? session.feed(k) : k.each_char { |c| session.feed(c) } }
+  end
+
+  def test_parse_fields_buttons_and_width
+    f = form("Name: <Name:10> <  City >\n[ Save ] [Cancel]\n")
+    assert_equal %w[Name City], f.names
+    assert_equal [0, 6, 10], f.slots[0].to_a.first(3)
+    assert_equal 9, f.slots[1].width # the width of "<  City >"
+    assert_equal %w[Save Cancel], f.buttons.map(&:label)
+    assert_equal ["Name: #{' ' * 10} #{' ' * 9}", '[ Save ] [Cancel]'], f.lines
+  end
+
+  def test_command_in_form_and_frame
+    f = form("<!echo hi!> <A>\n", frame: true)
+    assert_equal '│ hi     │', f.lines[1]
+    assert_equal [1, 5], f.slots.first.to_a.first(2)
+  end
+
+  def test_typing_and_navigation
+    s = Rdb::Mask::Session.new(form("<A:5> <B:5> [ OK ] [ Cancel ]\n"))
+    type(s, 'one', "\t", 'two', "\x7f", "\r")
+    assert_equal({ 'A' => 'one', 'B' => 'tw' }, s.values)
+    assert_equal :button, s.kind
+    assert_equal :accept, s.feed("\r")
+  end
+
+  def test_cancel_by_button_and_escape
+    s = Rdb::Mask::Session.new(form("<A:5> [ Save ] [ Abbrechen ]\n"))
+    s.feed("\e[Z")
+    assert_equal :cancel, s.feed(' ')
+    assert_equal :cancel, Rdb::Mask::Session.new(form("<A>\n")).feed("\e")
+  end
+
+  def test_enter_on_last_field_accepts_without_buttons
+    s = Rdb::Mask::Session.new(form("<A:3> <B:3>\n"))
+    assert_nil s.feed("\r")
+    assert_equal :accept, s.feed("\r")
+  end
+
+  def test_same_column_twice_is_one_field
+    s = Rdb::Mask::Session.new(form("<A:3> <A:3>\n"))
+    type(s, 'xy')
+    assert_equal({ 'A' => 'xy' }, s.values)
+    assert_equal %w[A], form("<A:3> <A:3>\n").names
+  end
+
+  def test_show_prints_picture_without_terminal
+    write('f', "Name: <Name:6>\n[ Save ] [ Cancel ]\n")
+    out = rdb('mask', '-s', file: 'f')
+    assert_includes out, "Name: ______\n[ Save ] [ Cancel ]"
+    assert_includes out, "  Name\trow 1 col 7 width 6"
+    assert_includes out, "  [Cancel]\trow 2 col 10 (cancels)"
+    assert_equal out, rdb('mask', '-s', 'f') # a file name works too
+  end
+
+  # Drive mask on a pseudo terminal; its table goes to a file, like in a pipe.
+  def run_on_pty(*keys)
+    out = File.join(@dir, 'mask.out')
+    result = nil
+    PTY.spawn({ 'PATH' => "#{BIN}:#{ENV['PATH']}" }, 'sh', '-c', "cd #{@dir} && mask < f > mask.out") do |r, w, pid|
+      sleep 0.5
+      keys.each do |k|
+        w.write k
+        sleep 0.1
+        r.read_nonblock(65_536) rescue nil
+      end
+      sleep 0.3
+      r.read_nonblock(65_536) rescue nil
+      _, st = Process.wait2(pid)
+      result = [File.exist?(out) ? File.read(out) : '', st.exitstatus]
+    end
+    result
+  end
+
+  def test_mask_on_a_terminal_writes_a_table
+    write('f', "Name: <Name:10>\nCity: <City:10>\n[ Save ] [ Cancel ]\n")
+    table, status = run_on_pty("Ann\r", "Rome\r", "\r")
+    assert_equal 0, status
+    assert_equal "Name\tCity\n----\t----\nAnn\tRome\n", table
+  end
+
+  def test_mask_cancel_writes_nothing
+    write('f', "Name: <Name:10>\n[ Save ] [ Cancel ]\n")
+    table, status = run_on_pty("Ann", "\e[Z", "\r")
+    assert_equal 1, status
+    assert_equal '', table
+  end
+end