Graphics.Vty.Input

This module provides the input layer for Vty, including methods for initializing an Input structure and reading Events from the terminal.

Note that due to the evolution of terminal emulators, some keys and combinations will not reliably map to the expected events by any terminal program. There is no 1:1 mapping from key events to bytes read from the terminal input device. In very limited cases the terminal and vty's input process can be customized to resolve these issues; see Graphics.Vty.Config for how to configure vty's input processing.

VTY's Implementation

There are two input modes:

1. 7-bit
2. 8-bit

The 7-bit input mode is the default and the expected mode in most use cases. This is what Vty uses.

7-bit input encoding

Control key combinations are represented by masking the two high bits of the 7-bit input. Historically the control key actually grounded the two high bit wires: 6 and 7. This is why control key combos map to single character events: the input bytes are identical. The input byte is the bit encoding of the character with bits 6 and 7 masked. Bit 6 is set by shift. Bit 6 and 7 are masked by control. For example,

• Control-I is i, `01101001`, and has bit 6 and 7 masked to become `00001001`, which is the ASCII and UTF-8 encoding of the Tab key.
• Control+Shift-C is C, `01000011`, with bit 6 and 7 set to zero which is `0000011` and is the "End of Text" code.
• Hypothesis: This is why capital-A, A, has value 65 in ASCII: this is the value 1 with bit 7 set and 6 unset.
• Hypothesis: Bit 6 is unset by upper case letters because, initially, there were only upper case letters used and a 5 bit encoding.

8-bit encoding

The 8th bit was originally used for parity checking which is useless for terminal emulators. Some terminal emulators support an 8-bit input encoding. While this provides some advantages, the actual usage is low. Most systems use 7-bit mode but recognize 8-bit control characters when escaped. This is what Vty does.

Escaped Control Keys

Using 7-bit input encoding, the ESC byte can signal the start of an encoded control key. To differentiate a single ESC event from a control key, the timing of the input is used.

1. ESC individually: ESC byte; no bytes following for a period of VMIN milliseconds.
2. Control keys that contain ESC in their encoding: The @ESC byte is followed by more bytes read within VMIN milliseconds. All bytes up until the next valid input block are passed to the classifier.

If the current runtime is the threaded runtime then the terminal's VMIN and VTIME behavior reliably implement the above rules. If the current runtime does not support forkOS then there is currently no implementation.

Unicode Input and Escaped Control Key Sequences

The input encoding determines how UTF-8 encoded characters are recognized.

• 7-bit mode: UTF-8 can be input unambiguiously. UTF-8 input is a superset of ASCII. UTF-8 does not overlap escaped control key sequences. However, the escape key must be differentiated from escaped control key sequences by the timing of the input bytes.
• 8-bit mode: UTF-8 cannot be input unambiguously. This does not require using the timing of input bytes to differentiate the escape key. Many terminals do not support 8-bit mode.

Terminfo

The terminfo system is used to determine how some keys are encoded. Terminfo is incomplete and in some cases terminfo is incorrect. Vty assumes terminfo is correct but provides a mechanism to override terminfo; see Graphics.Vty.Config, specifically inputOverrides.

Terminal Input is Broken

Clearly terminal input has fundemental issues. There is no easy way to reliably resolve these issues.

One resolution would be to ditch standard terminal interfaces entirely and just go directly to scancodes. This would be a reasonable option for Vty if everybody used the linux kernel console but for obvious reasons this is not possible.

The Graphics.Vty.Config module supports customizing the input-byte-to-event mapping and xterm supports customizing the scancode-to-input-byte mapping. With a lot of work a user's system can be set up to encode all the key combos in an almost-sane manner.

See also

• http://www.leonerd.org.uk/hacks/fixterms/

Documentation

data Key

Representations of non-modifier keys.

• KFun is indexed from 0 to 63. Range of supported FKeys varies by terminal and keyboard.
• KUpLeft, KUpRight, KDownLeft, KDownRight, KCenter support varies by terminal and keyboard.
• Actually, support for most of these but KEsc, KChar, KBS, and KEnter vary by terminal and keyboard.

Constructors

KEsc

KChar Char

KBS

KEnter

KLeft

KRight

KUp

KDown

KUpLeft

KUpRight

KDownLeft

KDownRight

KCenter

KFun Int

KBackTab

KPrtScr

KPause

KIns

KHome

KPageUp

KDel

KEnd

KPageDown

KBegin

KMenu

Instances

Eq Key

Defined in Graphics.Vty.Input.Events

Methods

(==) :: Key -> Key -> Bool

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

Ord Key

Defined in Graphics.Vty.Input.Events

Methods

compare :: Key -> Key -> Ordering

(<) :: Key -> Key -> Bool

(<=) :: Key -> Key -> Bool

(>) :: Key -> Key -> Bool

(>=) :: Key -> Key -> Bool

max :: Key -> Key -> Key

min :: Key -> Key -> Key

Read Key

Defined in Graphics.Vty.Input.Events

Methods

readsPrec :: Int -> ReadS Key

readList :: ReadS [Key]

readPrec :: ReadPrec Key

readListPrec :: ReadPrec [Key]

Show Key

Defined in Graphics.Vty.Input.Events

Methods

showsPrec :: Int -> Key -> ShowS

show :: Key -> String

showList :: [Key] -> ShowS

Generic Key

Defined in Graphics.Vty.Input.Events

Associated Types

type Rep Key :: Type -> Type

Methods

from :: Key -> Rep Key x

to :: Rep Key x -> Key

type Rep Key

Defined in Graphics.Vty.Input.Events

type Rep Key = D1 (MetaData "Key" "Graphics.Vty.Input.Events" "vty-5.29-I67jk1HctgABg2z7N86d9i" False) ((((C1 (MetaCons "KEsc" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "KChar" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Char)) :+: C1 (MetaCons "KBS" PrefixI False) (U1 :: Type -> Type))) :+: (C1 (MetaCons "KEnter" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "KLeft" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "KRight" PrefixI False) (U1 :: Type -> Type)))) :+: ((C1 (MetaCons "KUp" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "KDown" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "KUpLeft" PrefixI False) (U1 :: Type -> Type))) :+: (C1 (MetaCons "KUpRight" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "KDownLeft" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "KDownRight" PrefixI False) (U1 :: Type -> Type))))) :+: (((C1 (MetaCons "KCenter" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "KFun" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Int)) :+: C1 (MetaCons "KBackTab" PrefixI False) (U1 :: Type -> Type))) :+: (C1 (MetaCons "KPrtScr" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "KPause" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "KIns" PrefixI False) (U1 :: Type -> Type)))) :+: ((C1 (MetaCons "KHome" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "KPageUp" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "KDel" PrefixI False) (U1 :: Type -> Type))) :+: ((C1 (MetaCons "KEnd" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "KPageDown" PrefixI False) (U1 :: Type -> Type)) :+: (C1 (MetaCons "KBegin" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "KMenu" PrefixI False) (U1 :: Type -> Type))))))

data Modifier

Modifier keys. Key codes are interpreted such that users are more likely to have Meta than Alt; for instance on the PC Linux console, MMeta will generally correspond to the physical Alt key.

Constructors

MShift

MCtrl

MMeta

MAlt

Instances

Eq Modifier

Defined in Graphics.Vty.Input.Events

Methods

(==) :: Modifier -> Modifier -> Bool

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

Ord Modifier

Defined in Graphics.Vty.Input.Events

Methods

compare :: Modifier -> Modifier -> Ordering

(<) :: Modifier -> Modifier -> Bool

(<=) :: Modifier -> Modifier -> Bool

(>) :: Modifier -> Modifier -> Bool

(>=) :: Modifier -> Modifier -> Bool

max :: Modifier -> Modifier -> Modifier

min :: Modifier -> Modifier -> Modifier

Read Modifier

Defined in Graphics.Vty.Input.Events

Methods

readsPrec :: Int -> ReadS Modifier

readList :: ReadS [Modifier]

readPrec :: ReadPrec Modifier

readListPrec :: ReadPrec [Modifier]

Show Modifier

Defined in Graphics.Vty.Input.Events

Methods

showsPrec :: Int -> Modifier -> ShowS

show :: Modifier -> String

showList :: [Modifier] -> ShowS

Generic Modifier

Defined in Graphics.Vty.Input.Events

Associated Types

type Rep Modifier :: Type -> Type

Methods

from :: Modifier -> Rep Modifier x

to :: Rep Modifier x -> Modifier

type Rep Modifier

Defined in Graphics.Vty.Input.Events

type Rep Modifier = D1 (MetaData "Modifier" "Graphics.Vty.Input.Events" "vty-5.29-I67jk1HctgABg2z7N86d9i" False) ((C1 (MetaCons "MShift" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "MCtrl" PrefixI False) (U1 :: Type -> Type)) :+: (C1 (MetaCons "MMeta" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "MAlt" PrefixI False) (U1 :: Type -> Type)))

data Button

Mouse buttons.

Constructors

BLeft

BMiddle

BRight

BScrollUp

BScrollDown

Instances

Eq Button

Defined in Graphics.Vty.Input.Events

Methods

(==) :: Button -> Button -> Bool

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

Ord Button

Defined in Graphics.Vty.Input.Events

Methods

compare :: Button -> Button -> Ordering

(<) :: Button -> Button -> Bool

(<=) :: Button -> Button -> Bool

(>) :: Button -> Button -> Bool

(>=) :: Button -> Button -> Bool

max :: Button -> Button -> Button

min :: Button -> Button -> Button

Read Button

Defined in Graphics.Vty.Input.Events

Methods

readsPrec :: Int -> ReadS Button

readList :: ReadS [Button]

readPrec :: ReadPrec Button

readListPrec :: ReadPrec [Button]

Show Button

Defined in Graphics.Vty.Input.Events

Methods

showsPrec :: Int -> Button -> ShowS

show :: Button -> String

showList :: [Button] -> ShowS

Generic Button

Defined in Graphics.Vty.Input.Events

Associated Types

type Rep Button :: Type -> Type

Methods

from :: Button -> Rep Button x

to :: Rep Button x -> Button

type Rep Button

Defined in Graphics.Vty.Input.Events

type Rep Button = D1 (MetaData "Button" "Graphics.Vty.Input.Events" "vty-5.29-I67jk1HctgABg2z7N86d9i" False) ((C1 (MetaCons "BLeft" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "BMiddle" PrefixI False) (U1 :: Type -> Type)) :+: (C1 (MetaCons "BRight" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "BScrollUp" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "BScrollDown" PrefixI False) (U1 :: Type -> Type))))

data Event

Events.

Constructors

EvKey Key [Modifier]

A keyboard key was pressed with the specified modifiers.

EvMouseDown Int Int Button [Modifier]

A mouse button was pressed at the specified column and row. Any modifiers available in the event are also provided.

EvMouseUp Int Int (Maybe Button)

A mouse button was released at the specified column and row. Some terminals report only that a button was released without specifying which one; in that case, Nothing is provided. Otherwise Just the button released is included in the event.

EvResize Int Int

If read from eventChannel this is the size at the time of the signal. If read from nextEvent this is the size at the time the event was processed by Vty. Typically these are the same, but if somebody is resizing the terminal quickly they can be different.

EvPaste ByteString

A paste event occurs when a bracketed paste input sequence is received. For terminals that support bracketed paste mode, these events will be triggered on a paste event. Terminals that do not support bracketed pastes will send the paste contents as ordinary input (which is probably bad, so beware!) Note that the data is provided in raw form and you'll have to decode (e.g. as UTF-8) if that's what your application expects.

EvLostFocus

The terminal running the application lost input focus.

EvGainedFocus

The terminal running the application gained input focus.

Instances

Eq Event

Defined in Graphics.Vty.Input.Events

Methods

(==) :: Event -> Event -> Bool

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

Ord Event

Defined in Graphics.Vty.Input.Events

Methods

compare :: Event -> Event -> Ordering

(<) :: Event -> Event -> Bool

(<=) :: Event -> Event -> Bool

(>) :: Event -> Event -> Bool

(>=) :: Event -> Event -> Bool

max :: Event -> Event -> Event

min :: Event -> Event -> Event

Read Event

Defined in Graphics.Vty.Input.Events

Methods

readsPrec :: Int -> ReadS Event

readList :: ReadS [Event]

readPrec :: ReadPrec Event

readListPrec :: ReadPrec [Event]

Show Event

Defined in Graphics.Vty.Input.Events

Methods

showsPrec :: Int -> Event -> ShowS

show :: Event -> String

showList :: [Event] -> ShowS

Generic Event

Defined in Graphics.Vty.Input.Events

Associated Types

type Rep Event :: Type -> Type

Methods

from :: Event -> Rep Event x

to :: Rep Event x -> Event

type Rep Event

Defined in Graphics.Vty.Input.Events

type Rep Event = D1 (MetaData "Event" "Graphics.Vty.Input.Events" "vty-5.29-I67jk1HctgABg2z7N86d9i" False) ((C1 (MetaCons "EvKey" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Key) :*: S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 [Modifier])) :+: (C1 (MetaCons "EvMouseDown" PrefixI False) ((S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Int) :*: S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Int)) :*: (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Button) :*: S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 [Modifier]))) :+: C1 (MetaCons "EvMouseUp" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Int) :*: (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Int) :*: S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (Maybe Button)))))) :+: ((C1 (MetaCons "EvResize" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Int) :*: S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Int)) :+: C1 (MetaCons "EvPaste" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 ByteString))) :+: (C1 (MetaCons "EvLostFocus" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "EvGainedFocus" PrefixI False) (U1 :: Type -> Type))))

data Input

Constructors

Input

Fields

• _eventChannel :: TChan Event

  Channel of events direct from input processing. Unlike nextEvent this will not refresh the display if the next event is an EvResize.

• shutdownInput :: IO ()

  Shuts down the input processing. As part of shutting down the input, this should also restore the input state.

• restoreInputState :: IO ()

  Restore the terminal's input state to what it was prior to configuring input for Vty. This should be done as part of shutdownInput but is exposed in case you need to access it directly.

• _configRef :: IORef Config

  Changes to this value are reflected after the next event.

• _inputDebug :: Maybe Handle

  input debug log

inputForConfig :: Config -> IO Input

Set up the terminal with file descriptor inputFd for input. Returns an Input.

The table used to determine the Events to produce for the input bytes comes from classifyMapForTerm which is then overridden by the the applicable entries from the configuration's inputMap.

The terminal device's mode flags are configured by the attributeControl function.