ebiten/example/blocks/game_scene.go

package blocks

import (
	"github.com/hajimehoshi/go-ebiten/graphics"
	"github.com/hajimehoshi/go-ebiten/graphics/matrix"
	"github.com/hajimehoshi/go-ebiten/ui"
	"image/color"
	"math/rand"
	"time"
)

func init() {
	texturePaths["empty"] = "images/blocks/empty.png"
}

type GameScene struct {
	field             *Field
	rand              *rand.Rand
	currentPiece      *Piece
	currentPieceX     int
	currentPieceY     int
	currentPieceAngle Angle
	nextPiece         *Piece
}

func NewGameScene() *GameScene {
	return &GameScene{
		field: NewField(),
		rand:  rand.New(rand.NewSource(time.Now().UnixNano())),
	}
}

const emptyWidth = 16
const emptyHeight = 16
const fieldWidth = blockWidth * fieldBlockNumX
const fieldHeight = blockHeight * fieldBlockNumY

func (s *GameScene) choosePiece() *Piece {
	num := NormalBlockTypeNum
	blockType := BlockType(s.rand.Intn(num) + 1)
	return Pieces[blockType]
}

func (s *GameScene) Update(state *GameState) {
	if s.currentPiece == nil {
		s.currentPiece = s.choosePiece()
		x, y := s.currentPiece.InitialPosition()
		s.currentPieceX = x
		s.currentPieceY = y
		s.currentPieceAngle = Angle0
	}
	if state.Input.StateForKey(ui.KeySpace) == 1 {
		s.currentPieceAngle = s.field.RotatePieceRight(
			s.currentPiece, s.currentPieceX, s.currentPieceY,
			s.currentPieceAngle)
	}
	if l := state.Input.StateForKey(ui.KeyLeft);
	l == 1 || (10 <= l && l % 2 == 0) {
		s.currentPieceX = s.field.MovePieceToLeft(
			s.currentPiece, s.currentPieceX, s.currentPieceY,
			s.currentPieceAngle)
	}
	if r := state.Input.StateForKey(ui.KeyRight);
	r == 1 || (10 <= r && r % 2 == 0) {
		s.currentPieceX = s.field.MovePieceToRight(
			s.currentPiece, s.currentPieceX, s.currentPieceY,
			s.currentPieceAngle)
	}
	if d := state.Input.StateForKey(ui.KeyDown);
	(d - 1) % 2 == 0 {
		s.currentPieceY = s.field.DropPiece(
			s.currentPiece, s.currentPieceX, s.currentPieceY,
			s.currentPieceAngle)
	}
}

func (s *GameScene) Draw(context graphics.Context) {
	context.Fill(0xff, 0xff, 0xff)

	field := drawInfo.textures["empty"]
	geoMat := matrix.IdentityGeometry()
	geoMat.Scale(float64(fieldWidth)/float64(emptyWidth),
		float64(fieldHeight)/float64(emptyHeight))
	geoMat.Translate(20, 20) // magic number?
	colorMat := matrix.IdentityColor()
	colorMat.Scale(color.RGBA{0, 0, 0, 0x80})
	context.DrawTexture(field, geoMat, colorMat)

	geoMat = matrix.IdentityGeometry()
	geoMat.Translate(20, 20)
	s.field.Draw(context, geoMat)

	if s.currentPiece != nil {
		s.currentPiece.Draw(context, 20, 20,
			s.currentPieceX, s.currentPieceY, s.currentPieceAngle)
	}
}