brick-0.18: A declarative terminal user interface library

Safe Haskell | None
Language | Haskell2010

Brick.AttrMap

Contents

- Construction
- Finding attributes from names
- Manipulating attribute maps

Description

This module provides types and functions for managing an attribute map which maps attribute names (`AttrName`) to attributes (`Attr`). This module is designed to be used with the `OverloadedStrings` language extension to permit easy construction of `AttrName` values and you should also use `mappend` (`<>`) to combine names.

Attribute maps work by mapping hierarchical attribute names to attributes and inheriting parent names' attributes when child names specify partial attributes. Hierarchical names are created with `mappend`:

    let n = attrName "parent" <> attrName "child"

Attribute names are mapped to attributes, but some attributes may be partial (specify only a foreground or background color). When attribute name lookups occur, the attribute corresponding to a more specific name ('parent <> child' as above) is sucessively merged with the parent attribute (`parent` as above) all the way to the "root" of the attribute map, the map's default attribute. In this way, more specific attributes inherit what they don't specify from more general attributes in the same hierarchy. This allows more modularity and less repetition in specifying how elements of your user interface take on different attributes.

Synopsis

- data AttrMap
- data AttrName
- attrMap :: Attr -> [(AttrName, Attr)] -> AttrMap
- forceAttrMap :: Attr -> AttrMap
- attrName :: String -> AttrName
- attrMapLookup :: AttrName -> AttrMap -> Attr
- setDefault :: Attr -> AttrMap -> AttrMap
- applyAttrMappings :: [(AttrName, Attr)] -> AttrMap -> AttrMap
- mergeWithDefault :: Attr -> AttrMap -> Attr
- mapAttrName :: AttrName -> AttrName -> AttrMap -> AttrMap
- mapAttrNames :: [(AttrName, AttrName)] -> AttrMap -> AttrMap

# Documentation

data AttrMap Source #

An attribute map which maps `AttrName` values to `Attr` values.

Instances

Show AttrMap Source # |
Methods showsPrec :: Int -> AttrMap -> ShowS # show :: AttrMap -> String # showList :: [AttrMap] -> ShowS #

data AttrName Source #

An attribute name. Attribute names are hierarchical; use `mappend` (`<>`) to assemble them. Hierachy in an attribute name is used to represent increasing levels of specificity in referring to the attribute you want to use for a visual element, with names to the left being general and names to the right being more specific. For example:

    "window" <> "border"
    "window" <> "title"
    "header" <> "clock" <> "seconds"

Instances

Eq AttrName Source # |
Methods (==) :: AttrName -> AttrName -> Bool # (/=) :: AttrName -> AttrName -> Bool #
Ord AttrName Source # |
Methods compare :: AttrName -> AttrName -> Ordering # (<) :: AttrName -> AttrName -> Bool # (<=) :: AttrName -> AttrName -> Bool # (>) :: AttrName -> AttrName -> Bool # (>=) :: AttrName -> AttrName -> Bool # max :: AttrName -> AttrName -> AttrName # min :: AttrName -> AttrName -> AttrName #
Show AttrName Source # |
Methods showsPrec :: Int -> AttrName -> ShowS # show :: AttrName -> String # showList :: [AttrName] -> ShowS #
IsString AttrName Source # |
Methods fromString :: String -> AttrName #
Monoid AttrName Source # |
Methods mempty :: AttrName # mappend :: AttrName -> AttrName -> AttrName # mconcat :: [AttrName] -> AttrName #
GetAttr AttrName Source # |
Methods getAttr :: AttrName -> RenderM n Attr Source #

# Construction

attrMap Source #

Arguments

:: Attr | The map's default attribute to be returned when a name lookup fails, and the attribute that will be merged with successful lookups.
-> [(AttrName, Attr)] | The map's initial contents.
-> AttrMap |

Create an attribute map.

forceAttrMap :: Attr -> AttrMap Source #

Create an attribute map in which all lookups map to the same attribute.

attrName :: String -> AttrName Source #

Create an attribute name from a string.

# Finding attributes from names

attrMapLookup :: AttrName -> AttrMap -> Attr Source #

Look up the specified attribute name in the map. Map lookups proceed as follows. If the attribute map is forcing all lookups to a specific attribute, that attribute is returned. If the attribute name is empty, the map's default attribute is returned. If the attribute name is non-empty, very subsequence of names from the specified name are used to perform a lookup, and the results are combined as in `mergeWithDefault`, with more specific results taking precedence over less specific ones.

For example:

    attrMapLookup ("foo" <> "bar") (attrMap a []) == a
    attrMapLookup ("foo" <> "bar") (attrMap (bg blue) [("foo" <> "bar", fg red)]) == red `on` blue
    attrMapLookup ("foo" <> "bar") (attrMap (bg blue) [("foo" <> "bar", red on cyan)]) == red `on` cyan
    attrMapLookup ("foo" <> "bar") (attrMap (bg blue) [("foo" <> "bar", fg red), ("foo", bg cyan)]) == red `on` cyan
    attrMapLookup ("foo" <> "bar") (attrMap (bg blue) [("foo", fg red)]) == red `on` blue

# Manipulating attribute maps

setDefault :: Attr -> AttrMap -> AttrMap Source #

Set the default attribute value in an attribute map.

applyAttrMappings :: [(AttrName, Attr)] -> AttrMap -> AttrMap Source #

Insert a set of attribute mappings to an attribute map.

mergeWithDefault :: Attr -> AttrMap -> Attr Source #

Given an attribute and a map, merge the attribute with the map's default attribute. If the map is forcing all lookups to a specific attribute, the forced attribute is returned without merging it with the one specified here. Otherwise the attribute given here is merged with the attribute map's default attribute in that any aspect of the specified attribute that is not provided falls back to the map default. For example,

    mergeWithDefault (fg blue) $ attrMap (bg red) []

returns

    blue `on` red

mapAttrName :: AttrName -> AttrName -> AttrMap -> AttrMap Source #

Update an attribute map such that a lookup of `ontoName` returns the attribute value specified by `fromName`. This is useful for composite widgets with specific attribute names mapping those names to the sub-widget's expected name when calling that sub-widget's rendering function. See the ProgressBarDemo for an example usage, and `overrideAttr` for an alternate syntax.

mapAttrNames :: [(AttrName, AttrName)] -> AttrMap -> AttrMap Source #

Map several attributes to return the value associated with an alternate name. Applies `mapAttrName` across a list of mappings.