phi <- (1 + sqrt(5)) / 2
p <- ggplot(mtcars, aes(mpg, hp/10)) + geom_point()

test_that("window dimensions are in correct proportion", {
  
  # square axes & window
  b <- ggplot_build(p + coord_rect(ratio = 1))
  # expect_equal(
  #   diff(b$layout$panel_params[[1L]]$x$limits),
  #   diff(b$layout$panel_params[[1L]]$y$limits)
  # )
  expect_equal(
    diff(b$layout$panel_params[[1L]]$x.range),
    diff(b$layout$panel_params[[1L]]$y.range)
  )
  
  # golden rectangle axes & window
  b <- ggplot_build(p + coord_rect(ratio = 1 / phi))
  # expect_equal(
  #   diff(b$layout$panel_params[[1L]]$x$limits),
  #   diff(b$layout$panel_params[[1L]]$y$limits)
  # )
  expect_equal(
    diff(b$layout$panel_params[[1L]]$x.range),
    diff(b$layout$panel_params[[1L]]$y.range)
  )
  
  # square axes, golden rectangle window
  b <- ggplot_build(p + coord_rect(window_ratio = 1 / phi))
  # expect_equal(
  #   diff(b$layout$panel_params[[1L]]$y$limits) /
  #     diff(b$layout$panel_params[[1L]]$x$limits),
  #   1 / phi
  # )
  expect_equal(
    diff(b$layout$panel_params[[1L]]$y.range) / 
      diff(b$layout$panel_params[[1L]]$x.range),
    1 / phi
  )
  
  # 2x4 rectangle axes, golden rectangle window
  b <- ggplot_build(p + coord_rect(ratio = 1/2, window_ratio = 1 / phi))
  # expect_equal(
  #   diff(b$layout$panel_params[[1L]]$y$limits) /
  #     diff(b$layout$panel_params[[1L]]$x$limits),
  #   2 / phi
  # )
  expect_equal(
    diff(b$layout$panel_params[[1L]]$y.range) / 
      diff(b$layout$panel_params[[1L]]$x.range),
    2 / phi
  )
  
})