vty-5.16: A simple terminal UI library

Safe Haskell | Safe
Language | Haskell2010

Graphics.Vty.Attributes

Contents

- Styles
- Setting attribute colors
- Colors

Description

Display attributes

Attributes have three components: a foreground color, a background color, and a style mask. The simplest attribute is the default attribute, or `defAttr`. Attributes can be modified with `withForeColor`, `withBackColor`, and `withStyle`, e.g.,

        defAttr withForeColor red

`Image` constructors often require an `Attr` to indicate the attributes used in the image, e.g.,

        string (defAttr withForeColor red) "this text will be red"

The appearance of `Image`s using `defAttr` is determined by the The terminal, so this is not something VTY can control. The user is free to The define the color scheme of the terminal as they see fit.

The value `currentAttr` will keep the attributes of whatever was output previously.

Synopsis

- data Attr = Attr {
  - attrStyle :: !(MaybeDefault Style)
  - attrForeColor :: !(MaybeDefault Color)
  - attrBackColor :: !(MaybeDefault Color)
  }
- data FixedAttr = FixedAttr {
  - fixedStyle :: !Style
  - fixedForeColor :: !(Maybe Color)
  - fixedBackColor :: !(Maybe Color)
  }
- data MaybeDefault v where
  - Default :: MaybeDefault v
  - KeepCurrent :: MaybeDefault v
  - SetTo :: forall v. (Eq v, Show v, Read v) => !v -> MaybeDefault v
- defAttr :: Attr
- currentAttr :: Attr
- type Style = Word8
- withStyle :: Attr -> Style -> Attr
- standout :: Style
- underline :: Style
- reverseVideo :: Style
- blink :: Style
- dim :: Style
- bold :: Style
- defaultStyleMask :: Style
- styleMask :: Attr -> Word8
- hasStyle :: Style -> Style -> Bool
- withForeColor :: Attr -> Color -> Attr
- withBackColor :: Attr -> Color -> Attr
- data Color
  - = ISOColor !Word8
  - | Color240 !Word8
- black :: Color
- red :: Color
- green :: Color
- yellow :: Color
- blue :: Color
- magenta :: Color
- cyan :: Color
- white :: Color
- brightBlack :: Color
- brightRed :: Color
- brightGreen :: Color
- brightYellow :: Color
- brightBlue :: Color
- brightMagenta :: Color
- brightCyan :: Color
- brightWhite :: Color
- rgbColor :: Integral i => i -> i -> i -> Color

# Documentation

data Attr #

A display attribute defines the Color and Style of all the characters rendered after the attribute is applied.

At most 256 colors, picked from a 240 and 16 color palette, are possible for the background and foreground. The 240 colors and 16 colors are points in different palettes. See Color for more information.

Constructors

Attr |
Fields attrStyle :: !(MaybeDefault Style) attrForeColor :: !(MaybeDefault Color) attrBackColor :: !(MaybeDefault Color)

Instances

Eq Attr # |
Methods (==) :: Attr -> Attr -> Bool # (/=) :: Attr -> Attr -> Bool #
Read Attr # |
Methods readsPrec :: Int -> ReadS Attr # readList :: ReadS [Attr] # readPrec :: ReadPrec Attr # readListPrec :: ReadPrec [Attr] #
Show Attr # |
Methods showsPrec :: Int -> Attr -> ShowS # show :: Attr -> String # showList :: [Attr] -> ShowS #
Monoid Attr # |
Methods mempty :: Attr # mappend :: Attr -> Attr -> Attr # mconcat :: [Attr] -> Attr #

data FixedAttr #

Specifies the display attributes such that the final style and color values do not depend on the previously applied display attribute. The display attributes can still depend on the terminal's default colors (unfortunately).

Constructors

FixedAttr |
Fields fixedStyle :: !Style fixedForeColor :: !(Maybe Color) fixedBackColor :: !(Maybe Color)

Instances

Eq FixedAttr # |
Methods (==) :: FixedAttr -> FixedAttr -> Bool # (/=) :: FixedAttr -> FixedAttr -> Bool #
Show FixedAttr # |
Methods showsPrec :: Int -> FixedAttr -> ShowS # show :: FixedAttr -> String # showList :: [FixedAttr] -> ShowS #

data MaybeDefault v where #

The style and color attributes can either be the terminal defaults. Or be equivalent to the previously applied style. Or be a specific value.

Constructors

Default :: MaybeDefault v |
KeepCurrent :: MaybeDefault v |
SetTo :: forall v. (Eq v, Show v, Read v) => !v -> MaybeDefault v |

Instances

Eq v => Eq (MaybeDefault v) # |
Methods (==) :: MaybeDefault v -> MaybeDefault v -> Bool # (/=) :: MaybeDefault v -> MaybeDefault v -> Bool #
(Eq v, Show v, Read v) => Read (MaybeDefault v) # |
Methods readsPrec :: Int -> ReadS (MaybeDefault v) # readList :: ReadS [MaybeDefault v] # readPrec :: ReadPrec (MaybeDefault v) # readListPrec :: ReadPrec [MaybeDefault v] #
Eq v => Show (MaybeDefault v) # |
Methods showsPrec :: Int -> MaybeDefault v -> ShowS # show :: MaybeDefault v -> String # showList :: [MaybeDefault v] -> ShowS #
Eq v => Monoid (MaybeDefault v) # |
Methods mempty :: MaybeDefault v # mappend :: MaybeDefault v -> MaybeDefault v -> MaybeDefault v # mconcat :: [MaybeDefault v] -> MaybeDefault v #

defAttr :: Attr #

Sets the style, background color and foreground color to the default values for the terminal. There is no easy way to determine what the default background and foreground colors are.

currentAttr :: Attr #

Keeps the style, background color and foreground color that was previously set. Used to override some part of the previous style.

EG: current_style `withForeColor` brightMagenta

Would be the currently applied style (be it underline, bold, etc) but with the foreground color set to brightMagenta.

# Styles

type Style = Word8 #

Styles are represented as an 8 bit word. Each bit in the word is 1 if the style attribute assigned to that bit should be applied and 0 if the style attribute should not be applied.

withStyle :: Attr -> Style -> Attr #

Add the given style attribute

standout :: Style #

The 6 possible style attributes:

- standout
- underline
- reverseVideo
- blink
- dim
- bold/bright

(The invisible, protect, and altcharset display attributes some terminals support are not supported via VTY.)

underline :: Style #

The 6 possible style attributes:

- standout
- underline
- reverseVideo
- blink
- dim
- bold/bright

(The invisible, protect, and altcharset display attributes some terminals support are not supported via VTY.)

reverseVideo :: Style #

The 6 possible style attributes:

- standout
- underline
- reverseVideo
- blink
- dim
- bold/bright

(The invisible, protect, and altcharset display attributes some terminals support are not supported via VTY.)

blink :: Style #

The 6 possible style attributes:

- standout
- underline
- reverseVideo
- blink
- dim
- bold/bright

(The invisible, protect, and altcharset display attributes some terminals support are not supported via VTY.)

dim :: Style #

The 6 possible style attributes:

- standout
- underline
- reverseVideo
- blink
- dim
- bold/bright

(The invisible, protect, and altcharset display attributes some terminals support are not supported via VTY.)

bold :: Style #

The 6 possible style attributes:

- standout
- underline
- reverseVideo
- blink
- dim
- bold/bright

(The invisible, protect, and altcharset display attributes some terminals support are not supported via VTY.)

defaultStyleMask :: Style #

styleMask :: Attr -> Word8 #

hasStyle :: Style -> Style -> Bool #

true if the given Style value has the specified Style set.

# Setting attribute colors

withForeColor :: Attr -> Color -> Attr #

Set the foreground color of an `Attr`.

withBackColor :: Attr -> Color -> Attr #

Set the background color of an `Attr`.

# Colors

data Color #

Abstract data type representing a color.

Currently the foreground and background color are specified as points in either a:

- 16 color palette. Where the first 8 colors are equal to the 8 colors of the ISO 6429 (ANSI) 8 color palette and the second 8 colors are bright/vivid versions of the first 8 colors.
- 240 color palette. This palette is a regular sampling of the full RGB colorspace for the first 224 colors. The remaining 16 colors is a greyscale palette.

The 8 ISO 6429 (ANSI) colors are as follows:

1. black
2. red
3. green
4. yellow
5. blue
6. magenta
7. cyan
8. white

The mapping from points in the 240 color palette to colors actually displayable by the terminal depends on the number of colors the terminal claims to support. Which is usually determined by the terminfo "colors" property. If this property is not being accurately reported then the color reproduction will be incorrect.

If the terminal reports <= 16 colors then the 240 color palette points are only mapped to the 8 color pallete. I'm not sure of the RGB points for the "bright" colors which is why they are not addressable via the 240 color palette.

If the terminal reports > 16 colors then the 240 color palette points are mapped to the nearest points in a ("color count" - 16) subsampling of the 240 color palette.

All of this assumes the terminals are behaving similarly to xterm and rxvt when handling colors. And that the individual colors have not been remapped by the user. There may be a way to verify this through terminfo but I don't know it.

Seriously, terminal color support is INSANE.

Constructors

ISOColor !Word8 |
Color240 !Word8 |

Instances

Eq Color # |
Methods (==) :: Color -> Color -> Bool # (/=) :: Color -> Color -> Bool #
Read Color # |
Methods readsPrec :: Int -> ReadS Color # readList :: ReadS [Color] # readPrec :: ReadPrec Color # readListPrec :: ReadPrec [Color] #
Show Color # |
Methods showsPrec :: Int -> Color -> ShowS # show :: Color -> String # showList :: [Color] -> ShowS #

black :: Color #

Standard 8-color ANSI terminal color codes.

red :: Color #

Standard 8-color ANSI terminal color codes.

green :: Color #

Standard 8-color ANSI terminal color codes.

yellow :: Color #

Standard 8-color ANSI terminal color codes.

blue :: Color #

Standard 8-color ANSI terminal color codes.

magenta :: Color #

Standard 8-color ANSI terminal color codes.

cyan :: Color #

Standard 8-color ANSI terminal color codes.

white :: Color #

Standard 8-color ANSI terminal color codes.

brightBlack :: Color #

Bright/Vivid variants of the standard 8-color ANSI

brightRed :: Color #

Bright/Vivid variants of the standard 8-color ANSI

brightGreen :: Color #

Bright/Vivid variants of the standard 8-color ANSI

brightYellow :: Color #

Bright/Vivid variants of the standard 8-color ANSI

brightBlue :: Color #

brightMagenta :: Color #

brightCyan :: Color #

brightWhite :: Color #

rgbColor :: Integral i => i -> i -> i -> Color #

Create a Vty `Color` (in the 240 color set) from an RGB triple.