Test Suite for Render Area

render_area_tests.rb

describe RenderArea do
  define_helper :build_render_area do |args|
    # Size of DR default render area (1280x720)
    # This area is centered inside the allscreen area
    args.grid.w ||= 1280
    args.grid.h ||= 720
    # logical pixel size of the whole screen (i.e. size of the render canvas in DR)
    args.grid.allscreen_w ||= args.grid.w
    args.grid.allscreen_h ||= args.grid.h
    # actual pixel size of the whole screen
    args.grid.allscreen_w_px ||= args.grid.allscreen_w
    args.grid.allscreen_h_px ||= args.grid.allscreen_h
    RenderArea.new(grid: args.grid)
  end

  # dp is defined as: 1 inch = 160 dp
  # Screen Density = real screen pixels per inch
  describe '#dp_to_px' do
    it 'assumes screen density is 254' do
      area = build_render_area(args)

      assert.equal! area.dp_to_px(160), 254
    end

    it 'rounds up to full pixels' do
      area = build_render_area(args)

      assert.equal! area.dp_to_px(164), 261 # 164dp -> 260.35px -> 261px
    end

    it 'considers scale' do
      # scale 0.5
      args.grid.allscreen_w_px = 500
      args.grid.allscreen_w = 1000
      area = build_render_area(args)

      # screen is scaled half so you need double the pixels to get the same physical dp size
      assert.equal! area.dp_to_px(160), 508
    end
  end

  # 1 pt is defined as: 1 inch = 72 pt
  describe '#pt_to_px' do
    it 'assumes screen density is 254' do
      area = build_render_area(args)

      assert.equal! area.pt_to_px(72), 254
    end

    it 'rounds up to full pixels' do
      area = build_render_area(args)

      assert.equal! area.pt_to_px(80), 283 # 80pt -> 282.22px -> 283px
    end

    it 'considers scale' do
      # scale 0.5
      args.grid.allscreen_w_px = 500
      args.grid.allscreen_w = 1000
      area = build_render_area(args)

      # screen is scaled half so you need double the pixels to get the same physical dp size
      assert.equal! area.pt_to_px(72), 508
    end
  end

  describe '#px_to_dp' do
    it 'assumes screen density is 254' do
      area = build_render_area(args)

      assert.equal! area.px_to_dp(254), 160
    end

    it 'does not round' do
      area = build_render_area(args)

      assert.equal! area.px_to_dp(131).round(2), 82.52
    end

    it 'considers scale' do
      # scale 0.5
      args.grid.allscreen_w_px = 500
      args.grid.allscreen_w = 1000
      area = build_render_area(args)

      # screen is scaled half so you need double the pixels to get the same physical dp size
      assert.equal! area.px_to_dp(508), 160
    end
  end

  describe '#w' do
    it 'returns width in dp' do
      args.grid.allscreen_w = 254
      area = build_render_area(args)

      assert.equal! area.w, 160
    end
  end

  describe '#h' do
    it 'returns height in dp' do
      args.grid.allscreen_h = 254
      area = build_render_area(args)

      assert.equal! area.h, 160
    end
  end

  describe '#px_coordinates' do
    it 'converts dp coordinates/rects to px' do
      args.grid.w = 254
      args.grid.h = 254
      args.grid.allscreen_w = 254 * 3
      args.grid.allscreen_h = 254 * 3
      area = build_render_area(args)

      [
        { value: { x: 0, y: 0 }, expected: { x: -254, y: -254 } },
        { value: { x: 160, y: 160 }, expected: { x: 0, y: 0 } },
        { value: { x: 320, y: 320 }, expected: { x: 254, y: 254 } },
        { value: { x: 0, y: 0, w: 160, h: 160 }, expected: { x: -254, y: -254, w: 254, h: 254 } },
        { value: { x: 160, y: 160, w: 160, h: 160 }, expected: { x: 0, y: 0, w: 254, h: 254 } }
      ].each do |test_case|
        assert.equal! area.px_coordinates(test_case[:value]),
                      test_case[:expected],
                      "Expected #{test_case[:value]} to be converted to #{test_case[:expected]}"
      end
    end
  end

  describe '#dp_coordinates' do
    it 'converts px coordinates/rects to dp' do
      args.grid.w = 254
      args.grid.h = 254
      args.grid.allscreen_w = 254 * 3
      args.grid.allscreen_h = 254 * 3
      area = build_render_area(args)

      [
        { value: { x: -254, y: -254 }, expected: { x: 0, y: 0 } },
        { value: { x: 0, y: 0 }, expected: { x: 160, y: 160 } },
        { value: { x: 254, y: 254 }, expected: { x: 320, y: 320 } },
        { value: { x: -254, y: -254, w: 254, h: 254 }, expected: { x: 0, y: 0, w: 160, h: 160 } },
        { value: { x: 0, y: 0, w: 254, h: 254 }, expected: { x: 160, y: 160, w: 160, h: 160 } }
      ].each do |test_case|
        assert.equal! area.dp_coordinates(test_case[:value]),
                      test_case[:expected],
                      "Expected #{test_case[:value]} to be converted to #{test_case[:expected]}"
      end
    end
  end

  describe '#tick' do
    it 'applies updated grid values' do
      area = build_render_area(args)
      original_rect = { x: 20, y: 30, w: 40, h: 50 }
      before_change = area.px_coordinates(original_rect)

      args.grid.allscreen_w_px *= 2
      args.grid.allscreen_h_px *= 2
      args.grid.w /= 2
      args.grid.h /= 2

      after_change = area.px_coordinates(original_rect)
      # Because tick has not yet been called it will be the same
      assert.equal! before_change, after_change

      area.tick

      after_tick = area.px_coordinates(original_rect)
      assert.not_equal! before_change, after_tick
    end
  end
end