func newCanvas(canvasEl *dom.HTMLCanvasElement) *canvas {
c := &canvas{canvasEl: canvasEl, event: make(chan string)}
canvasEl.AddEventListener("keydown", false, func(event dom.Event) {
c.handleKeyDown(event.(*dom.KeyboardEvent))
})
canvasEl.AddEventListener("keyup", false, func(event dom.Event) {
c.handleKeyUp(event.(*dom.KeyboardEvent))
})
go func() {
ticker := time.NewTicker(time.Duration(1000/animationFramesPerSecond) * time.Millisecond)
for {
<-ticker.C
c.draw()
if c.checkLost() {
c.bll = nil
c.event <- "L"
} else {
c.checkTopBottomCollision()
c.checkPaddleCollision()
if c.checkOverNet() {
rad := math.Atan2(c.bll.yMovement, c.bll.xMovement)
deg := rad * radianToDegree
if deg < 0 {
deg = 360 + deg
}
speed := math.Floor(c.bll.xMovement/math.Cos(rad) + 0.5)
if speed < 2 {
speed = 2
}
c.event <- fmt.Sprintf("N,%d,%d,%d", c.bll.yPos, int(deg), int(speed))
c.bll = nil
}
}
}
}()
return c
}
