MDN web docs にある 「そのままのJavaScriptを使ったブロックくずしゲーム」 の4番目のステップ。
lesson04
aki:~/breakout$ cp -r lesson03/ lesson04
aki:~/breakout$ cd lesson04/
aki:~/breakout/lesson04$
lesson03 をコピーした lesson04 を用意して続きを始める。
今回は パドルとキーボード操作
ボールにぶつかるパドルを定義する
そういうわけで、ボールに当てるパドルが必要になりました。パドルに用いるいくつかの変数を定義しましょう。次の変数を、他の変数と一緒にコードの一番上に追加してください。
var paddleHeight = 10; var paddleWidth = 75; var paddleX = (canvas.width-paddleWidth)/2;
paddleHeight と paddleWidth は変化しないので定数でいいな。 考えたらballRadiusも変化しないので定数でよかった。
ほかにMaybeが複数あるのは面倒なので1つにしてついでに状態を表示しておこう。
module Breakout (component) where
import Prelude
import CSS (background, block, display, margin, marginBottom, marginLeft, marginRight, marginTop, padding, px, rgb)
import CSS.Common (auto)
import Control.Monad.Rec.Class (forever)
import Data.Maybe (Maybe(..))
import Data.Time.Duration (Milliseconds(..))
import Effect (Effect)
import Effect.Aff as Aff
import Effect.Aff.Class (class MonadAff)
import Graphics.Canvas (CanvasElement, Dimensions)
import Graphics.Canvas as Canvas
import Halogen as H
import Halogen.HTML as HH
import Halogen.HTML.CSS (style)
import Halogen.HTML.Properties as HP
import Halogen.Subscription as HS
import Math as Math
canvasId :: String
canvasId = "myCanvas"
paddleHeight = 10.0 :: Number
paddleWidth = 75.0 :: Number
ballRadius = 10.0 :: Number
type Dataset
= { x :: Number
, y :: Number
, dx :: Number
, dy :: Number
, paddleX :: Number
}
type State
= { maybeCanvas :: Maybe CanvasElement
, dataset :: Dataset
}
data Action
= Initialize
| Tick
component :: forall query input output m. MonadAff m => H.Component query input output m
component =
H.mkComponent
{ initialState
, render
, eval:
H.mkEval
$ H.defaultEval
{ handleAction = handleAction
, initialize = Just Initialize
}
}
initialState :: forall i. i -> State
initialState _ =
{ maybeCanvas: Nothing
, dataset:
{ x: 0.0
, y: 0.0
, dx: 0.0
, dy: 0.0
, paddleX: 0.0
}
}
render :: forall m. State -> H.ComponentHTML Action () m
render state =
HH.main
[ style do
margin (px 0.0) (px 0.0) (px 0.0) (px 0.0)
padding (px 0.0) (px 0.0) (px 0.0) (px 0.0)
]
[ HH.canvas
[ style do
background (rgb 238 238 238)
display block
marginTop (px 0.0)
marginRight auto
marginBottom (px 0.0)
marginLeft auto
, HP.id canvasId
, HP.width 480
, HP.height 320
]
, HH.text $ show state.dataset
]
handleAction :: forall output m. MonadAff m => Action -> H.HalogenM State Action () output m Unit
handleAction = case _ of
Initialize -> do
init <- H.liftEffect initialize
H.put init
-- timer
_ <- H.subscribe =<< timer Tick
pure unit
Tick -> do
(state :: State) <- H.get
case state.maybeCanvas of
Nothing -> pure unit
Just canvas -> do
newDataset <- H.liftEffect $ draw canvas state.dataset
H.modify_ \st -> st { dataset = newDataset }
where
initialize :: Effect State
initialize =
Canvas.getCanvasElementById canvasId
>>= case _ of
Nothing -> pure $ initialState unit
Just canvas -> do
dim <- Canvas.getCanvasDimensions canvas
pure
{ maybeCanvas: Just canvas
, dataset:
{ x: dim.width / 2.0
, y: dim.height - 30.0
, dx: 2.0
, dy: (-2.0)
, paddleX: (dim.width - paddleWidth) / 2.0
}
}
draw :: CanvasElement -> Dataset -> Effect Dataset
draw canvas dataset = do
dim <- H.liftEffect $ Canvas.getCanvasDimensions canvas
ctx <- Canvas.getContext2D canvas
--
Canvas.clearRect ctx { x: 0.0, y: 0.0, width: dim.width, height: dim.height }
drawBall
drawPaddle dim
pure $ nextDataset dim
where
drawBall :: Effect Unit
drawBall = do
ctx <- Canvas.getContext2D canvas
--
Canvas.beginPath ctx
Canvas.arc ctx
{ x: dataset.x
, y: dataset.y
, radius: ballRadius
, start: 0.0
, end: Math.pi * 2.0
}
Canvas.setFillStyle ctx "#0095DD"
Canvas.fill ctx
Canvas.closePath ctx
drawPaddle :: Dimensions -> Effect Unit
drawPaddle { height: height } = do
ctx <- Canvas.getContext2D canvas
--
Canvas.beginPath ctx
Canvas.rect ctx
{ x: dataset.paddleX
, y: height - paddleHeight
, width: paddleWidth
, height: paddleHeight
}
Canvas.setFillStyle ctx "#0095DD"
Canvas.fill ctx
Canvas.closePath ctx
nextDataset :: Dimensions -> Dataset
nextDataset c =
let
{ x: x, y: y, dx: dx, dy: dy } = dataset
r = ballRadius
in
dataset
{ x = x + dx
, y = y + dy
, dx =
if between (0.0 + r) (c.width - r) (x + dx) then
dx
else
(-dx)
, dy =
if between (0.0 + r) (c.height - r) (y + dy) then
dy
else
(-dy)
}
timer :: forall m a. MonadAff m => a -> m (HS.Emitter a)
timer val = do
{ emitter, listener } <- H.liftEffect HS.create
_ <-
H.liftAff $ Aff.forkAff
$ forever do
Aff.delay $ Milliseconds 10.0
H.liftEffect $ HS.notify listener val
pure emitter
コンパイラに従っているだけで順調にすすむ。
パドルを操作できるようにする
HandleKeyDown ev
| KE.key ev == "Right" || KE.key ev == "ArrowRight" -> do
H.liftEffect $ E.preventDefault (KE.toEvent ev)
H.modify_ \st -> st { dataset { rightPressed = true } }
| KE.key ev == "Left" || KE.key ev == "ArrowLeft" -> do
H.liftEffect $ E.preventDefault (KE.toEvent ev)
H.modify_ \st -> st { dataset { leftPressed = true } }
| otherwise -> pure unit
HandleKeyUp ev
| KE.key ev == "Right" || KE.key ev == "ArrowRight" -> do
H.liftEffect $ E.preventDefault (KE.toEvent ev)
H.modify_ \st -> st { dataset { rightPressed = false } }
| KE.key ev == "Left" || KE.key ev == "ArrowLeft" -> do
H.liftEffect $ E.preventDefault (KE.toEvent ev)
H.modify_ \st -> st { dataset { leftPressed = false } }
| otherwise -> pure unit
パドルの移動ロジック
左カーソルが押されていたら7ピクセル左に動き、右カーソルが押されていたら7ピクセル右に動きます。これだけでも良さそうですが、どちらかのキーを長く押し続けたらパドルがCanvasの縁から消えてしまいます。コードを次のように変えることでCanvasの境界内でのみ動くように改善できます。
if(rightPressed && paddleX < canvas.width-paddleWidth) { paddleX += 7; } else if(leftPressed && paddleX > 0) { paddleX -= 7; }
左カーソルが押されていたら7ピクセル左に動き、右カーソルが押されていたら7ピクセル右に動きます。 これはそのまま実装して
どちらかのキーを長く押し続けたらパドルがCanvasの縁から消えてしまいます。 この問題には (clamp関数)[https://pursuit.purescript.org/packages/purescript-prelude/5.0.1/docs/Data.Ord#v:clamp]でCanvasの境界内にとどめておくことにした。
nextDataset c =
let
{ x: x, y: y, dx: dx, dy: dy } = dataset
r = ballRadius
newPaddleX = case { left: dataset.leftPressed, right: dataset.rightPressed } of
{ left: false, right: true } -> dataset.paddleX + 7.0
{ left: true, right: false } -> dataset.paddleX - 7.0
_ -> dataset.paddleX
in
dataset
{ x = x + dx
, y = y + dy
, dx =
if between (0.0 + r) (c.width - r) (x + dx) then
dx
else
(-dx)
, dy =
if between (0.0 + r) (c.height - r) (y + dy) then
dy
else
(-dy)
, paddleX = clamp 0.0 (c.width - paddleWidth) newPaddleX
}
結果こうなる。
module Breakout (component) where
import Prelude
import CSS (background, block, display, margin, marginBottom, marginLeft, marginRight, marginTop, padding, px, rgb)
import CSS.Common (auto)
import Control.Monad.Rec.Class (forever)
import Data.Maybe (Maybe(..))
import Data.Time.Duration (Milliseconds(..))
import Effect (Effect)
import Effect.Aff as Aff
import Effect.Aff.Class (class MonadAff)
import Graphics.Canvas (CanvasElement, Dimensions)
import Graphics.Canvas as Canvas
import Halogen as H
import Halogen.HTML as HH
import Halogen.HTML.CSS (style)
import Halogen.HTML.Properties as HP
import Halogen.Query.Event (eventListener)
import Halogen.Subscription as HS
import Math as Math
import Web.Event.Event as E
import Web.HTML (window)
import Web.HTML.HTMLDocument as HTMLDocument
import Web.HTML.Window as Window
import Web.UIEvent.KeyboardEvent as KE
import Web.UIEvent.KeyboardEvent.EventTypes as KET
canvasId :: String
canvasId = "myCanvas"
paddleHeight = 10.0 :: Number
paddleWidth = 75.0 :: Number
ballRadius = 10.0 :: Number
type Dataset
= { x :: Number
, y :: Number
, dx :: Number
, dy :: Number
, paddleX :: Number
, leftPressed :: Boolean
, rightPressed :: Boolean
}
type State
= { maybeCanvas :: Maybe CanvasElement
, dataset :: Dataset
}
data Action
= Initialize
| Tick
| HandleKeyDown KE.KeyboardEvent
| HandleKeyUp KE.KeyboardEvent
component :: forall query input output m. MonadAff m => H.Component query input output m
component =
H.mkComponent
{ initialState
, render
, eval:
H.mkEval
$ H.defaultEval
{ handleAction = handleAction
, initialize = Just Initialize
}
}
initialState :: forall i. i -> State
initialState _ =
{ maybeCanvas: Nothing
, dataset:
{ x: 0.0
, y: 0.0
, dx: 0.0
, dy: 0.0
, paddleX: 0.0
, leftPressed: false
, rightPressed: false
}
}
render :: forall m. State -> H.ComponentHTML Action () m
render state =
HH.main
[ style do
margin (px 0.0) (px 0.0) (px 0.0) (px 0.0)
padding (px 0.0) (px 0.0) (px 0.0) (px 0.0)
]
[ HH.canvas
[ style do
background (rgb 238 238 238)
display block
marginTop (px 0.0)
marginRight auto
marginBottom (px 0.0)
marginLeft auto
, HP.id canvasId
, HP.width 480
, HP.height 320
]
, HH.text $ show state.dataset
]
handleAction :: forall output m. MonadAff m => Action -> H.HalogenM State Action () output m Unit
handleAction = case _ of
Initialize -> do
init <- H.liftEffect initialize
H.put init
-- keyboard event
document <- H.liftEffect $ Window.document =<< window
H.subscribe' \_ ->
eventListener
KET.keydown
(HTMLDocument.toEventTarget document)
(map HandleKeyDown <<< KE.fromEvent)
H.subscribe' \_ ->
eventListener
KET.keyup
(HTMLDocument.toEventTarget document)
(map HandleKeyUp <<< KE.fromEvent)
-- timer
_ <- H.subscribe =<< timer Tick
pure unit
Tick -> do
(state :: State) <- H.get
case state.maybeCanvas of
Nothing -> pure unit
Just canvas -> do
newDataset <- H.liftEffect $ draw canvas state.dataset
H.modify_ \st -> st { dataset = newDataset }
HandleKeyDown ev
| KE.key ev == "Right" || KE.key ev == "ArrowRight" -> do
H.liftEffect $ E.preventDefault (KE.toEvent ev)
H.modify_ \st -> st { dataset { rightPressed = true } }
| KE.key ev == "Left" || KE.key ev == "ArrowLeft" -> do
H.liftEffect $ E.preventDefault (KE.toEvent ev)
H.modify_ \st -> st { dataset { leftPressed = true } }
| otherwise -> pure unit
HandleKeyUp ev
| KE.key ev == "Right" || KE.key ev == "ArrowRight" -> do
H.liftEffect $ E.preventDefault (KE.toEvent ev)
H.modify_ \st -> st { dataset { rightPressed = false } }
| KE.key ev == "Left" || KE.key ev == "ArrowLeft" -> do
H.liftEffect $ E.preventDefault (KE.toEvent ev)
H.modify_ \st -> st { dataset { leftPressed = false } }
| otherwise -> pure unit
where
initialize :: Effect State
initialize =
Canvas.getCanvasElementById canvasId
>>= case _ of
Nothing -> pure $ initialState unit
Just canvas -> do
dim <- Canvas.getCanvasDimensions canvas
pure
{ maybeCanvas: Just canvas
, dataset:
{ x: dim.width / 2.0
, y: dim.height - 30.0
, dx: 2.0
, dy: (-2.0)
, paddleX: (dim.width - paddleWidth) / 2.0
, leftPressed: false
, rightPressed: false
}
}
draw :: CanvasElement -> Dataset -> Effect Dataset
draw canvas dataset = do
dim <- H.liftEffect $ Canvas.getCanvasDimensions canvas
ctx <- Canvas.getContext2D canvas
--
Canvas.clearRect ctx { x: 0.0, y: 0.0, width: dim.width, height: dim.height }
drawBall
drawPaddle dim
pure $ nextDataset dim
where
drawBall :: Effect Unit
drawBall = do
ctx <- Canvas.getContext2D canvas
--
Canvas.beginPath ctx
Canvas.arc ctx
{ x: dataset.x
, y: dataset.y
, radius: ballRadius
, start: 0.0
, end: Math.pi * 2.0
}
Canvas.setFillStyle ctx "#0095DD"
Canvas.fill ctx
Canvas.closePath ctx
drawPaddle :: Dimensions -> Effect Unit
drawPaddle { height: height } = do
ctx <- Canvas.getContext2D canvas
--
Canvas.beginPath ctx
Canvas.rect ctx
{ x: dataset.paddleX
, y: height - paddleHeight
, width: paddleWidth
, height: paddleHeight
}
Canvas.setFillStyle ctx "#0095DD"
Canvas.fill ctx
Canvas.closePath ctx
nextDataset :: Dimensions -> Dataset
nextDataset c =
let
{ x: x, y: y, dx: dx, dy: dy } = dataset
r = ballRadius
newPaddleX = case { left: dataset.leftPressed, right: dataset.rightPressed } of
{ left: false, right: true } -> dataset.paddleX + 7.0
{ left: true, right: false } -> dataset.paddleX - 7.0
_ -> dataset.paddleX
in
dataset
{ x = x + dx
, y = y + dy
, dx =
if between (0.0 + r) (c.width - r) (x + dx) then
dx
else
(-dx)
, dy =
if between (0.0 + r) (c.height - r) (y + dy) then
dy
else
(-dy)
, paddleX = clamp 0.0 (c.width - paddleWidth) newPaddleX
}
timer :: forall m a. MonadAff m => a -> m (HS.Emitter a)
timer val = do
{ emitter, listener } <- H.liftEffect HS.create
_ <-
H.liftAff $ Aff.forkAff
$ forever do
Aff.delay $ Milliseconds 10.0
H.liftEffect $ HS.notify listener val
pure emitter
これでleftPressedがtrueなら左へ, rightPressedがtrueなら右へと
きちんとパドルを操作できている。
GitHubリポジトリ
コードはGitHub上にあります。
https://github.com/ak1211/breakout
まだつづく
よてい