| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Brick.AttrMap
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.
- 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
Documentation
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"
Construction
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.
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