26_motion.cr

require "../src/sdl"
require "../src/image"

SDL.init(SDL::Init::VIDEO); at_exit { SDL.quit }
SDL::IMG.init(SDL::IMG::Init::PNG); at_exit { SDL::IMG.quit }

SCREEN_WIDTH = 640
SCREEN_HEIGHT = 480

window = SDL::Window.new("SDL tutorial", SCREEN_WIDTH, SCREEN_HEIGHT)
renderer = SDL::Renderer.new(window, SDL::Renderer::Flags::ACCELERATED | SDL::Renderer::Flags::PRESENTVSYNC)

class Dot
  WIDTH = 20
  HEIGHT = 20
  VELOCITY = 10

  def initialize(@renderer : SDL::Renderer, @mPosX = 0, @mPosY = 0, @mVelX = 0, @mVelY = 0)
    image = SDL::IMG.load(File.join(__DIR__, "data", "dot.bmp"))
    image.color_key = {0, 255, 255}
    @texture = SDL::Texture.from(image, @renderer)
  end

  def handle_event(event : SDL::Event)
    if event.keydown? && event.repeat == 0
      case event.sym
      when .up?
        @mVelY -= VELOCITY
      when .down?
        @mVelY += VELOCITY
      when .left?
        @mVelX -= VELOCITY
      when .right?
        @mVelX += VELOCITY
      end
    elsif event.keyup? && event.repeat == 0
      case event.sym
      when .up?
        @mVelY += VELOCITY
      when .down?
        @mVelY -= VELOCITY
      when .left?
        @mVelX += VELOCITY
      when .right?
        @mVelX -= VELOCITY
      end
    end 
  end

  def move
    @mPosX += @mVelX
    if (@mPosX < 0) || (@mPosX + WIDTH > SCREEN_WIDTH)
      @mPosX -= @mVelX
    end

    @mPosY += @mVelY
    if (@mPosY < 0) || (@mPosY + HEIGHT > SCREEN_HEIGHT)
      @mPosY -= @mVelY
    end
  end

  def render
    @renderer.copy(@texture, nil, {@mPosX, @mPosY, @texture.width, @texture.height})
  end
end

dot = Dot.new(renderer)

loop do
  case event = SDL::Event.poll
  when SDL::Event::Quit
    break
  when SDL::Event::Keyboard
    dot.handle_event(event)
  end

  dot.move
  renderer.draw_color = {255, 255, 255, 255}
  renderer.clear
  dot.render
  renderer.present
end