50 lines
1.3 KiB
Elixir
50 lines
1.3 KiB
Elixir
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defmodule DancingDots.Animation do
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@type dot :: DancingDots.Dot.t()
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@type opts :: keyword
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@type error :: any
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@type frame_number :: pos_integer
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@callback init(opts) :: {:ok, opts} | {:error, error}
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@callback handle_frame(dot, frame_number, opts) :: dot
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defmacro __using__(_) do
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quote do
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@behaviour DancingDots.Animation
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def init(opts), do: {:ok, opts}
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defoverridable init: 1
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end
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end
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end
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defmodule DancingDots.Flicker do
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use DancingDots.Animation
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@impl DancingDots.Animation
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def handle_frame(%DancingDots.Dot{opacity: opacity} = dot, frame_number, _opts)
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when rem(frame_number, 4) == 0,
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do: %{dot | opacity: opacity / 2}
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@impl DancingDots.Animation
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def handle_frame(dot, _frame_number, _opts), do: dot
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end
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defmodule DancingDots.Zoom do
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use DancingDots.Animation
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@impl DancingDots.Animation
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def init(opts) do
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case Keyword.get(opts, :velocity) do
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velocity when is_number(velocity) ->
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{:ok, opts}
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velocity ->
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{:error,
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"The :velocity option is required, and its value must be a number. Got: #{inspect(velocity)}"}
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end
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end
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@impl DancingDots.Animation
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def handle_frame(%DancingDots.Dot{radius: radius} = dot, frame_number, opts),
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do: %{dot | radius: radius + (frame_number - 1) * Keyword.get(opts, :velocity)}
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end
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