Plushie.Canvas.Element (Plushie v0.7.0)

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Behaviour for canvas elements.

Canvas elements are the building blocks of canvas drawing. Like widgets, they produce tree nodes, but they operate in the canvas domain: positioned by coordinates rather than layout, drawn by the canvas renderer rather than the widget renderer.

Declaring an element

defmodule MyApp.Canvas.Star do
  use Plushie.Canvas.Element

  element :star do
    field :x, :float
    field :y, :float
    field :radius, :float
    field :points, :integer, default: 5
    field :fill, Plushie.Type.Color
  end
end

Generated code

The macro generates:

  • new/1 auto-ID constructor (new(opts)) for use inside canvas blocks where the container assigns IDs automatically
  • new/2 constructor with explicit ID (new(id, opts))
  • Setter functions per field for pipeline composition
  • with_options/2 for applying keyword options via setters
  • build/1 for explicit ui_node() conversion
  • type_name/0 returning the element type string
  • encode/1 for backward compatibility with Plushie.Type.encode_value
  • @type t, @type option typespecs
  • Plushie.Tree.Node protocol implementation

Container elements

Pass container: true for group-like elements that hold children:

element :group, container: true do
  field :opacity, :float
end

Container elements get push/2 and extend/2 for adding children, and new/2 accepts a :do option for inline children.