vty-5.2.1: A simple terminal UI library

Safe HaskellNone




data Output Source




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 DisplayContext Source




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

writeUtf8Text :: ByteString -> WriteSource

All terminals serialize UTF8 text to the terminal device exactly as serialized in memory.

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

Displays the given Picture.

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

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

data CursorOutputMap Source

The cursor position is given in X,Y character offsets. Due to multi-column characters this needs to be translated to column, row positions.




charToOutputPos :: (Int, Int) -> (Int, Int)

limitAttrForDisplay :: Output -> Attr -> AttrSource

Not all terminals support all display attributes. This filters a display attribute to what the given terminal can display.