boon - unix terminal framework

Boon is an alternative to curses. It occupies a similar level of abstraction (somewhere between terminfo and your application), but uses different concepts. It is just over 100loc and has no dependencies outside the standard library.

The high level API aims to be declarative and is partly inspired by react. The lines of the terminal are represented as a list of strings. On each update, this list is regenerated and compared to the previous version. Only the lines that have changed are rendered to the terminal.

Boon does not provide utilities for color and styling. You can either use the low level API or a third party library such as colorama or blessings.

Example

import boon

class Example(boon.App):
  def render(self, rows, cols):
    yield 'Hello World'

  def on_key(self, key):
    if key == 'q':
      self.running = False

example = Example()
example.run()

High level API

App.run()

Call to start the main loop.

App.running

Set to False to stop the main loop.

App.selector

In instance of selectors.DefaultSelector you can use to register additional file objects to the main loop.

App.render(rows, cols)

Overwrite to define your view. For every line in the UI, this functions should yield a string.

App.on_key(key)

Overwrite to react to key presses. key is a string containing either a character or an escape sequence. Boon contains constants for the most common escape sequences:

• KEY_BACKSPACE
• KEY_ESC
• KEY_HOME
• KEY_END
• KEY_PPAGE
• KEY_NPAGE
• KEY_UP
• KEY_DOWN
• KEY_RIGHT
• KEY_LEFT

Note that boon reads all available input, so in rare occasions key might contain more than one key. This should not be an issue in practice though.

Low level API

get_cap(cap, *args) -> str

Get a capability from the terminfo database. If stdout is not a tty or if the capability is not supported by the terminal this returns an empty string. The full list of capabilities is available in the terminfo manpage

print(get_cap('setaf', 13) + 'foo' + get_cap('sgr0'))

move(y, x)

Move the cursor to the given position.

tty_restore(fd)

Context manager that restores tty settings after the nested block.

def getpass(prompt):
  fd = sys.stdin.fileno()
  with tty_restore(fd):
    flags = termios.tcgetattr(fd)
    flags[3] &= ~termios.ECHO
    termios.tcsetattr(fd, termios.TCSADRAIN, flags)
    return input(prompt)

fullscreen()

Context manager that enters cup and cbreak mode and also hides the cursor. Everything is restored to the previous state after the nested block.

getch() -> string

Read from stdin. This is non-blocking. See App.on_key() for details on the return value.