Graphics.Vty

Vty supports input and output to terminal devices.

• Input to the terminal is provided to the app as a sequence of Events.

• The output is defined by a Picture. Which is one or more layers of Images.

  • The module Graphics.Vty.Image provides a number of constructor equations that will build correct Image values. See string, <|>, and <-> for starters.
  • The constructors in Graphics.Vty.Image.Internal should not be used.
• Images can be styled using Attr. See Graphics.Vty.Attributes.

See the vty-examples package for a number of examples.

 main = do
     vty <- mkVty def
     let line0 = string (def withForeColor green) "first line"
         line1 = string (def withBackColor blue) "second line"
         img = line0 <-> line1
         pic = picForImage img
     update vty pic
     e :: Event <- nextEvent vty
     shutdown vty
     print $ "Last event was: " ++ show e

Good sources of documentation for terminal programming are:

• https://github.com/b4winckler/vim/blob/master/src/term.c
• http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
• http://ulisse.elettra.trieste.it/services/doc/serial/config.html
• http://www.leonerd.org.uk/hacks/hints/xterm-8bit.html
• http://www.unixwiz.net/techtips/termios-vmin-vtime.html
• vt100 control sequences

Documentation

data Vty

The main object. At most one should be created.

The use of Vty typically follows this process:

1. initialize vty

   1. use the update equation of Vty to display a picture
   2. repeat
   3. shutdown vty.

An alternative to tracking the Vty instance is to use withVty in Graphics.Vty.Inline.Unsafe.

This does not assure any thread safety. In theory, as long as an update action is not executed when another update action is already then it's safe to call this on multiple threads.

todo Remove explicit shutdown requirement.

Constructors

Vty

Fields

update :: Picture -> IO ()

Outputs the given Picture. Equivalent to outputPicture applied to a display context implicitly managed by Vty. The managed display context is reset on resize.

nextEvent :: IO Event

Get one Event object, blocking if necessary. This will refresh the terminal if the event is a EvResize.

inputIface :: Input

The input interface. See Input

outputIface :: Output

The output interface. See Output

refresh :: IO ()

Refresh the display. nextEvent will refresh the display if a resize occurs. If other programs output to the terminal and mess up the display then the application might want to force a refresh.

shutdown :: IO ()

Clean up after vty. The above methods will throw an exception if executed after this is executed.

mkVty :: Config -> IO Vty

Set up the state object for using vty. At most one state object should be created at a time for a given terminal device.

The specified config is added to the userConfig. With the userConfig taking precedence. See Graphics.Vty.Config

For most applications mkVty def is sufficient.

module Graphics.Vty.Config

module Graphics.Vty.Input

module Graphics.Vty.Output

module Graphics.Vty.Picture

type DisplayRegion = (Int, Int)

Named alias for a Int pair