Graphics.Vty.Output

Documentation

outputForCurrentTerminal :: (Applicative m, MonadIO m) => Config -> m Output

Returns a Output for the current terminal as determined by TERM.

The specific Output implementation used is hidden from the API user. All terminal implementations are assumed to perform more, or less, the same. Currently all implementations use terminfo for at least some terminal specific information. This is why platforms without terminfo are not supported. However, as mentioned before, any specifics about it being based on terminfo are hidden from the API user. If a terminal implementation is developed for a terminal for a platform without terminfo support then Vty should work as expected on that terminal.

Selection of a terminal is done as follows:

• If TERM == xterm then the terminal might be one of the Mac OS X .app terminals. Check if that might be the case and use MacOSX if so. otherwise use XTermColor.

  • for any other TERM value TerminfoBased is used.

To differentiate between Mac OS X terminals this uses the TERM_PROGRAM environment variable. However, an xterm started by Terminal or iTerm *also* has TERM_PROGRAM defined since the environment variable is not reset/cleared by xterm. However a Terminal.app or iTerm.app started from an xterm under X11 on mac os x will likely be done via open. Since this does not propogate environment variables (I think?) this assumes that XTERM_VERSION will never be set for a true Terminal.app or iTerm.app session.

The file descriptor used for output will a be a duplicate of the current stdout file descriptor.

todo add an implementation for windows that does not depend on terminfo. Should be installable with only what is provided in the haskell platform. Use ansi-terminal

outputForNameAndIO :: (Applicative m, MonadIO m) => String -> Handle -> m Output

gives an output method structure for a terminal with the given name and the given Handle.

setCursorPos :: MonadIO m => Output -> Int -> Int -> m ()

Sets the cursor position to the given output column and row.

This is not necessarially the same as the character position with the same coordinates. Characters can be a variable number of columns in width.

Currently, the only way to set the cursor position to a given character coordinate is to specify the coordinate in the Picture instance provided to outputPicture or refresh.

hideCursor :: MonadIO m => Output -> m ()

Hides the cursor

showCursor :: MonadIO m => Output -> m ()

Shows the cursor

data Output

Constructors

Output

Fields

terminalID :: String

Text identifier for the output device. Used for debugging.

releaseTerminal :: MonadIO m => m ()

reserveDisplay :: MonadIO m => m ()

Clear the display and initialize the terminal to some initial display state.

The expectation of a program is that the display starts in some initial state. The initial state would consist of fixed values:

• cursor at top left
• UTF-8 character encoding
• drawing characteristics are the default

The abstract operation I think all these behaviors are instances of is reserving exclusive access to a display such that:

• The previous state cannot be determined
• When exclusive access to a display is released the display returns to the previous state.

releaseDisplay :: MonadIO m => m ()

Return the display to the state before reserveDisplay If no previous state then set the display state to the initial state.

displayBounds :: MonadIO m => m DisplayRegion

Returns the current display bounds.

outputByteBuffer :: ByteString -> IO ()

Output the byte string to the terminal device.

contextColorCount :: Int

Maximum number of colors supported by the context.

supportsCursorVisibility :: Bool

if the cursor can be shown / hidden

assumedStateRef :: IORef AssumedState

mkDisplayContext :: MonadIO m => Output -> DisplayRegion -> m DisplayContext

Acquire display access to the given region of the display. Currently all regions have the upper left corner of (0,0) and the lower right corner at (max displayWidth providedWidth, max displayHeight providedHeight)

data AssumedState

Constructors

AssumedState

Fields

prevFattr :: Maybe FixedAttr

prevOutputOps :: Maybe DisplayOps

data DisplayContext

Constructors

DisplayContext

Fields

contextDevice :: Output

contextRegion :: DisplayRegion

Provide the bounds of the display context.

writeMoveCursor :: Int -> Int -> Write

writeShowCursor :: Write

writeHideCursor :: Write

writeSetAttr :: FixedAttr -> Attr -> DisplayAttrDiff -> Write

writeDefaultAttr :: Write

Reset the display attributes to the default display attributes

writeRowEnd :: Write

inlineHack :: IO ()

See inlineHack

outputPicture :: MonadIO m => DisplayContext -> Picture -> m ()

Displays the given Picture.

1. The image is cropped to the display size.

   1. Converted into a sequence of attribute changes and text spans.
   2. The cursor is hidden.
   3. Serialized to the display.
   4. The cursor is then shown and positioned or kept hidden.

todo: specify possible IO exceptions. abstract from IO monad to a MonadIO instance.

displayContext :: MonadIO m => Output -> DisplayRegion -> m DisplayContext