Graphics.Vty

Vty provides interfaces for both terminal input and terminal output.

• Input to the terminal is provided to the Vty application as a sequence of Events.
• Output is provided to Vty by the application in the form of a Picture. A Picture is one or more layers of Images. Image values can be built by the various constructors in Graphics.Vty.Image. Output can be syled using Attr (attribute) values in the Graphics.Vty.Attributes module.

Vty uses threads internally, so programs made with Vty need to be compiled with the threaded runtime using the GHC -threaded option.

 import Graphics.Vty

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

Documentation

data Vty

A Vty value represents a handle to the Vty library that the application must create in order to use Vty.

The use of Vty typically follows this process:

1. Initialize vty with mkVty (this takes control of the terminal).
2. Use update to display a picture.
3. Use nextEvent to get the next input event.
4. Depending on the event, go to 2 or 5.
5. Shutdown vty and restore the terminal state with shutdown. At this point the Vty handle cannot be used again.

Operations on Vty handles are not thread-safe.

Constructors

Vty

Fields

• update :: Picture -> IO ()

  Outputs the given Picture.

• nextEvent :: IO Event

  Return the next Event or block until one becomes available.

• nextEventNonblocking :: IO (Maybe Event)

  Non-blocking version of nextEvent.

• inputIface :: Input

  The input interface. See Input.

• outputIface :: Output

  The output interface. See Output.

• refresh :: IO ()

  Refresh the display. If other programs output to the terminal and mess up the display then the application might want to force a refresh using this function.

• shutdown :: IO ()

  Clean up after vty. A call to this function is necessary to cleanly restore the terminal state before application exit. The above methods will throw an exception if executed after this is executed. Idempotent.

• isShutdown :: IO Bool

mkVty :: Config -> IO Vty

Create a Vty handle. At most one handle should be created at a time for a given terminal device.

The specified configuration is added to the the configuration loaded by userConfig with the userConfig configuration taking precedence. See Graphics.Vty.Config.

For most applications mkVty defaultConfig is sufficient.

setWindowTitle :: Vty -> String -> IO ()

Set the terminal window title string.

This function emits an Xterm-compatible escape sequence that we anticipate will work for essentially all modern terminal emulators. Ideally we'd use a terminal capability for this, but there does not seem to exist a termcap for setting window titles. If you find that this function does not work for a given terminal emulator, please report the issue.

For details, see:

https://tldp.org/HOWTO/Xterm-Title-3.html

data Mode

Modal terminal features that can be enabled and disabled.

Constructors

Mouse

Mouse mode (whether the terminal is configured to provide mouse input events)

BracketedPaste

Paste mode (whether the terminal is configured to provide events on OS pastes)

Focus

Focus-in/focus-out events (whether the terminal is configured to provide events on focus change)

Hyperlink

Hyperlink mode via the withURL attribute modifier (see https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda). Note that this may not work gracefully in all terminal emulators so be sure to test this mode with the terminals you intend to support. It is off by default.

Instances

Eq Mode

Defined in Graphics.Vty.Output.Interface

Methods

(==) :: Mode -> Mode -> Bool

(/=) :: Mode -> Mode -> Bool

Read Mode

Defined in Graphics.Vty.Output.Interface

Methods

readsPrec :: Int -> ReadS Mode

readList :: ReadS [Mode]

readPrec :: ReadPrec Mode

readListPrec :: ReadPrec [Mode]

Show Mode

Defined in Graphics.Vty.Output.Interface

Methods

showsPrec :: Int -> Mode -> ShowS

show :: Mode -> String

showList :: [Mode] -> ShowS

module Graphics.Vty.Config

module Graphics.Vty.Input

module Graphics.Vty.Output

module Graphics.Vty.Output.Interface

module Graphics.Vty.Picture

module Graphics.Vty.Image

module Graphics.Vty.Attributes