Add Train Simulator app

octopus/lib/octopus/apps/train.ex

@@ -0,0 +1,59 @@
+defmodule Octopus.Apps.Train do
+  use Octopus.App
+
+  alias Octopus.{Canvas, Image}
+  alias Octopus.Protobuf.InputEvent
+
+  @landscape Image.list_images() |> hd()
+  @fps 60
+
+  defmodule State do
+    defstruct [:canvas, :time, :x, :acceleration, :speed]
+  end
+
+  def name(), do: "Train Simulator"
+
+  def init(_args) do
+    canvas = Image.load(@landscape)
+
+    :timer.send_interval(trunc(1000 / @fps), :tick)
+
+    {:ok, %State{canvas: canvas, time: 0, x: 0, acceleration: 0, speed: 0}}
+  end
+
+  def add_window_corners(canvas) do
+    window_locations = for x <- 0..9*(8+16)//(8+16), do: {x, 0}
+
+    Enum.reduce(window_locations, canvas, fn {x, y}, canvas ->
+        canvas
+          |> Canvas.put_pixel({x, y}, [0, 0, 0])
+          |> Canvas.put_pixel({x+7, y}, [0, 0, 0])
+          |> Canvas.put_pixel({x, y+7}, [0, 0, 0])
+          |> Canvas.put_pixel({x+7, y+7}, [0, 0, 0])
+      end)
+  end
+
+  def handle_info(:tick, %State{} = state) do
+    canvas2 = state.canvas |> Canvas.translate({trunc(state.x), 0}, true)
+
+    canvas2
+      |> add_window_corners()
+      |> Canvas.to_frame(drop: true)
+      |> send_frame()
+
+    speed = state.speed + state.acceleration/@fps
+    speed = min(10, max(-10, speed)) # Limit speed
+    speed = speed*(1/(1+(0.1/@fps))) # Apply friction
+
+    {:noreply, %State{state | time: state.time + 1/@fps, speed: speed, x: state.x + speed}}
+  end
+
+  def handle_input(%InputEvent{type: :AXIS_X_1, value: value}, state) do
+    state = %State{state | acceleration: -0.1*value}
+    {:noreply, state}
+  end
+
+  def handle_input(%InputEvent{type: _, value: _}, state) do
+    {:noreply, state}
+  end
+end

octopus/lib/octopus/canvas.ex

@@ -169,8 +169,8 @@ defmodule Octopus.Canvas do
     pixels =
       for x <- 0..(width - 1),
           y <- 0..(height - 1),
-          new_x = rem(x + dx, width),
-          new_y = rem(y + dy, height),
+          new_x = Integer.mod(x + dx, width),
+          new_y = Integer.mod(y + dy, height),
           into: %{},
           do: {{new_x, new_y}, Canvas.get_pixel(canvas, {x, y})}