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module Rubyvis
# Alias por Rubyvis::Anchor.new(target)
def self.Anchor(target)
Rubyvis::Anchor.new(target)
end
# Represents an anchor on a given mark. An anchor is itself a mark, but
# without a visual representation. It serves only to provide useful default
# properties that can be inherited by other marks. Each type of mark can define
# any number of named anchors for convenience. If the concrete mark type does
# not define an anchor implementation specifically, one will be inherited from
# the mark's parent class.
#
# For example, the bar mark provides anchors for its four sides: left,
# right, top and bottom. Adding a label to the top anchor of a bar,
#
# bar.anchor("top").add(Rubyvis::Label)
#
# will render a text label on the top edge of the bar; the top anchor defines
# the appropriate position properties (top and left), as well as text-rendering
# properties for convenience (text_align and text_baseline).
#
# <p>Note that anchors do not <i>inherit</i> from their targets; the positional
# properties are copied from the scene graph, which guarantees that the anchors
# are positioned correctly, even if the positional properties are not defined
# deterministically. (In addition, it also improves performance by avoiding
# re-evaluating expensive properties.) If you want the anchor to inherit from
# the target, use Mark#extend before adding. For example:
#
# bar.anchor("top").extend(bar).add(Rubyvis::Label)
#
# The anchor defines it's own positional properties, but other properties (such
# as the title property, say) can be inherited using the above idiom. Also note
# that you can override positional properties in the anchor for custom
# behavior.
class Anchor < Mark
# List of properties common to all Anchors
@properties=Mark.properties.dup
##
# :attr: name
# The anchor name. The set of supported anchor names is dependent on the
# concrete mark type; see the mark type for details. For example, bars support
# left, right, top and bottom anchors.
#
# While anchor names are typically constants, the anchor name is a true
# property, which means you can specify a function to compute the anchor name
# dynamically. For instance, if you wanted to alternate top and bottom anchors, saying
#
# m.anchor(lambda {(index % 2) ? "top" : "bottom"}).add(Rubyvis::Dot)
#
# would have the desired effect.
#
attr_accessor_dsl [:name, lambda {|d| d.to_s}]
# Create a new Anchor. Use Mark.add instead.
def initialize(target)
self.target=target
self.parent=target.parent
super()
end
# Sets the prototype of this anchor to the specified mark. Any properties not
# defined on this mark may be inherited from the specified prototype mark, or
# its prototype, and so on. The prototype mark need not be the same type of
# mark as this mark. (Note that for inheritance to be useful, properties with
# the same name on different mark types should have equivalent meaning.)
#
# <p>This method differs slightly from the normal mark behavior in that the
# anchor's target is preserved.
#
# @param {Rubyvis::Mark} proto the new prototype.
# @returns {Rubyvis::Anchor} this anchor.
# @see Rubyvis.Mark#add
def mark_extend(proto)
@proto=proto
self
end
end
end
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