-- love2d perspective demo
-- request love2d 11.3

function love.load()
  tp = require "perspective"

  love.graphics.setDefaultFilter("linear", "linear", 2)
  wdw_w, wdw_h = love.graphics.getDimensions()

  -- img = love.graphics.newImage("uvcheckermap01-512.png")
  img = love.graphics.newImage("scifitex02_tex.png")

  w0, w1 = 300, 1200
  x0 = wdw_w / 2 - w0 / 2
  x1 = wdw_w / 2 - w1 / 2
  y0, y1 = wdw_h / 2, wdw_h
  v = { {x0, y0}, {x0 + w0, y0}, {x1 + w1, y1}, {x1, y1} }

  -- tp:setRepeat( {0.25, 0.25}, {0.75, 0.75} )

  -- local ih = img:getHeight()
  -- tp:setRepeat( {253 / ih, 50 /ih}, {80 / ih, 80 / ih} )

  love.graphics.setBackgroundColor(0.2, 0.4, 0.8, 1.0)

  bg_x = 0
  bg_w = 100
  guide = true
end

function love.update(dt)
  bg_x = (bg_x + 200 * dt) % w0
  local scale = w1 / w0
  v[1][1] = (wdw_w / 2) - bg_x
  v[4][1] = (wdw_w / 2) - (bg_x * scale)
  v[2][1] = v[1][1] + w0
  v[3][1] = v[4][1] + w0 * scale
end

function love.draw()
  -- draw perspective quad
  love.graphics.setColor(1, 1, 1, 1)
  tp:setShaderOnly(img, v[1], v[2], v[3], v[4])
  love.graphics.rectangle("fill", 0, wdw_h / 2, wdw_w, wdw_h / 2)
  tp:off()

  -- draw guide
  if guide then
    love.graphics.setColor(0, 1, 0, 0.25)
    love.graphics.polygon("fill", v[1][1], v[1][2], v[2][1], v[2][2], v[3][1], v[3][2], v[4][1], v[4][2], v[1][1], v[1][2])
  end

  -- print FPS
  love.graphics.setColor(1, 1, 1, 1)
  love.graphics.print("FPS: "..love.timer.getFPS(), 4, 4)
  love.graphics.print("G key : Guide on/off", 4, 24)
end

function love.keypressed(key, isrepeat)
  -- ESC to exit
  if key == "escape" then love.event.quit() end
  if key == "g" then guide = not guide end
end