NAME

       "Tickit::Pen" - store a collection of rendering attributes

DESCRIPTION

       A pen instance stores a collection of rendering attributes for text to display. It comes
       in two forms, mutable and immutable. Both types of pen are subclasses of the base
       "Tickit::Pen" class.

       An immutable pen is an instance of "Tickit::Pen::Immutable". Its attributes are set by the
       constructor and are fixed thereafter. Methods are provided to query the presence or value
       of attributes, and to fetch the entire set as a hash.

       A mutable pen is an instance of "Tickit::Pen::Mutable". Its attributes may be set by the
       constructor, and can be changed at any time. As well as supporting the same query methods
       as immutable pens, more methods are provided to change or remove them.

       While mutable pens may initially seem more useful, they can complicate logic due to their
       shared referential nature. If the same mutable pen is shared across multiple places, care
       needs to be taken to redraw anything that depends on it if it is ever changed. If pens
       need sharing, especially if results are cached for performance, consider using immutable
       pens to simplify the logic.

   Attributes
       The following named pen attributes are supported:

       fg => COL
       bg => COL
               Foreground or background colour. "COL" may be an integer or one of the eight
               colour names. A colour name may optionally be prefixed by "hi-" for the high-
               intensity version (may not be supported by all terminals). Some terminals may
               support a palette of 256 colours instead, some 16, and some only 8. The pen object
               will not check this as it cannot be reliably detected in all cases.

       fg:rgb8 => STRING
       bg:rgb8 => STRING
               Foreground or background colour secondary RGB8 specification. The value is a
               string encoding the three 8-bit values in hexadecimal notation, prefixed by a hash
               ("#") symbol; for example

                  #13579B

               On input, either lower- or upper-case is accepted; on output the letters will be
               upper-case.

               These attribute can only be set if the corresponding regular index attribute is
               also set. Changing or clearing the regular index will also clear the RGB8 version.

               Applications wishing to use this attribute should be aware that the majority of
               terminal drivers will not be able to support it, and so should make sure to set an
               appropriate regular colour index as well. Some terminals using the xterm driver
               may make use of it, however, and therefore ignore the index version.

       b => BOOL
       u => BOOL
       i => BOOL
       rv => BOOL
       strike => BOOL
       blink => BOOL
               Bold, underline, italics, reverse video, strikethrough, blink.

       af => INT
               Alternate font.

       Note that not all terminals can render the italics, strikethrough, or alternate font
       attributes.

CONSTRUCTORS

   new
          $pen = Tickit::Pen->new( %attrs )

       Returns a new pen, initialised from the given attributes.

       Currently this method returns a "Tickit::Pen::Mutable", though this may change in a future
       version. It is provided for backward-compatibility for code that expects to be able to
       construct a "Tickit::Pen" directly.

          $pen = Tickit::Pen::Immutable->new( %attrs )

          $pen = Tickit::Pen::Mutable->new( %attrs )

       Return a new immutable, or mutable pen, initialised from the given attributes.

   new_from_attrs
          $pen = Tickit::Pen->new_from_attrs( $attrs )

       Returns a new pen, initialised from keys in the given HASH reference. Used keys are
       deleted from the hash.

       Currently this method returns a "Tickit::Pen::Mutable", though this may change in a future
       version. It is provided for backward-compatibility for code that expects to be able to
       construct a "Tickit::Pen" directly.

          $pen = Tickit::Pen::Immutable->new_from_attrs( $attrs )

          $pen = Tickit::Pen::Mutable->new_from_attrs( $attrs )

       Return a new immutable, or mutable pen, initialised from the given attributes.

   as_mutable
   clone
          $pen = $orig->as_mutable

          $pen = $orig->clone

       Returns a new mutable pen, initialised by copying the attributes of the original.

       "clone" is provided as a legacy alias, but may be removed in a future version.

   as_immutable
          $pen = $orig->as_immutable

       Returns an immutable pen, initialised by copying the attributes of the original. When
       called on an immutable pen, this method just returns the same pen instance.

   mutable
          $is_mutable = $pen->mutable

       Returns true on mutable pens and false on immutable ones.

METHODS ON ALL PENS

       The following query methods apply to both immutable and mutable pens.

   hasattr
          $exists = $pen->hasattr( $attr )

       Returns true if the given attribute exists on this object

   getattr
          $value = $pen->getattr( $attr )

       Returns the current value of the given attribute

   getattrs
          %values = $pen->getattrs

       Returns a key/value list of all the attributes

   equiv_attr
          $equiv = $pen->equiv_attr( $other, $attr )

       Returns true if the two pens have the equivalent values for the given attribute; that is,
       either both define it to the same value, or neither defines it.

   equiv
          $equiv = $pen->equiv( $other )

       Returns true if the two pens have equivalent values for all attributes.

METHODS ON MUTABLE PENS

       The following mutation methods exist on mutable pens.

   chattr
          $pen->chattr( $attr, $value )

       Change the value of an attribute. Setting "undef" deletes the attribute entirely. See also
       "delattr".

   chattrs
          $pen->chattrs( \%attrs )

       Change the values of all the attributes given in the hash. Recgonised attributes will be
       deleted from the hash.

   delattr
          $pen->delattr( $attr )

       Delete an attribute from this pen. This attribute will no longer be modified by this pen.

   copy_from
   default_from
          $pen->copy_from( $other )

          $pen->default_from( $other )

       Copy attributes from the given pen. "copy_from" will override attributes already defined
       by $pen; "default_from" will only copy attributes that are not yet defined by $pen.

       As a convenience both methods return $pen.

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>