CRT for Ncurses

A Crystal library of Ncurses widgets for building terminal user interfaces for legacy application.

Please Note: This library is currently on the back burner while devlopment of a new pure ANSI based CRT library is developed. Eventually this library will be modiied to act as an alternate backend for CRT proper.

CRT Ncurses provides 23 ready-to-use widgets — from simple labels and buttons to scrolling lists, text editors, menus, file selectors, and spreadsheet-style grids — all rendered with ncurses.

CRT Ncruses is a heavy modified ported of Ruby CDK, which is itself a port of the CDK C libary.

Widgets

Widget	Description
Label	Static text display
Dialog	Message box with buttons
Entry	Single-line text input
MultiEntry	Multi-line text editor
Button	Standalone push button
ButtonBox	Group of buttons
Scale(T)	Numeric input with arrow keys — generic over any number type
Slider(T)	Slider bar — generic over any number type
Scroll	Scrolling list
Radio	Radio button list
Selection	Multi-select checklist
ItemList	Cycle through a list of values
Template	Formatted input with overlay template
Histogram	Horizontal/vertical bar chart
Graph	Line/plot graph
Calendar	Date picker
Marquee	Scrolling marquee text
ScrollWindow	Scrolling text output window
Viewer	Text file viewer with buttons
Menu	Menu bar with pull-down submenus
AlphaList	Filterable alphabetical list
FileSelect	File/directory selector
Matrix	Spreadsheet-style editable grid

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     crt:
       github: trans/crt

2. Run shards install

Requires ncurses development headers (libncurses-dev, ncurses-devel, or equivalent for your system).

Usage

require "crt/ncurses"

# Initialize ncurses
CRT::Ncurses.start

# Create a screen
screen = CRT::Ncurses::Screen.new

# Display a label
label = CRT::Ncurses::Label.new(screen,
  x: CRT::Ncurses::CENTER, y: CRT::CENTER,
  message: ["[b]Hello, CRT![/]", "Press any key to exit."],
  box: true, shadow: true)

label.draw
label.wait(0)

# Clean up
label.destroy
screen.destroy
CRT::Ncurses.end

Format Strings

CRT::Ncurses provides a BBCode-style format string system for styled text. Use CRT::Ncurses.fmt to convert a format string into a chtype array for display.

# Bold text
CRT::Ncurses.fmt("[b]Hello![/]")

# Combined attributes and colors
CRT::Ncurses.fmt("[bold #0F]Status:[/] OK")

# Alignment (at string start)
CRT::Ncurses.fmt("[C][b]Centered Title[/]")

Attributes

Short	Long	Effect
[b]	[bold]	Bold
[u]	[underline]	Underline
[dim]	[dim]	Dim
[rev]	[reverse]	Reverse video
[so]	[standout]	Standout
[bk]	[blink]	Blink

Multiple attributes can be combined in one tag: [b u]

Colors

Colors use hex palette indices (00-FF, 256-color terminal palette):

Notation	Meaning
#XX	Foreground color
##XX	Background color
#XX/YY	Foreground / background
##YY/XX	Background / foreground

CRT::Ncurses.fmt("[#0F]green text[/]")
CRT::Ncurses.fmt("[#FF/00]white on black[/]")
CRT::Ncurses.fmt("[b #0F/00]bold green on black[/]")

Alignment

Place at the start of the string:

Short	Long
[C]	[center]
[R]	[right]
[L]	[left]

Style Stack

• [/] — pop the last style (restores previous attributes/colors)
• [//] — reset all styles
• \[ — literal open bracket

Named Styles

Register reusable styles with CRT.style:

CRT::Ncurses.style("error", "bold #FF ##00")
CRT::Ncurses.style("header", "bold underline #0F")

CRT::Ncurses.fmt("[error]Oops![/] Something broke")
CRT::Ncurses.fmt("[header]Welcome[/]")

Development

crystal spec                                   # Run tests
crystal build src/crt/ncurses.cr --no-codegen  # Type-check without building

Contributing

1. Fork it (https://github.com/trans/crt-ncurses/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

License

MIT