mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-12-25 03:08:54 +01:00
314 lines
6.9 KiB
Go
314 lines
6.9 KiB
Go
// Copyright 2018 The Ebiten Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build example jsgo
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package main
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import (
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"bytes"
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"image"
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"image/color"
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_ "image/png"
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"log"
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"math/rand"
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"time"
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"github.com/hajimehoshi/ebiten"
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"github.com/hajimehoshi/ebiten/ebitenutil"
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"github.com/hajimehoshi/ebiten/examples/resources/images"
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"github.com/hajimehoshi/ebiten/inpututil"
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)
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func init() {
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rand.Seed(time.Now().UnixNano())
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}
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const (
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screenWidth = 320
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screenHeight = 240
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)
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// Sprite represents an image.
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type Sprite struct {
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image *ebiten.Image
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x int
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y int
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}
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// In returns true if (x, y) is in the sprite, and false otherwise.
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func (s *Sprite) In(x, y int) bool {
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// Check the actual color (alpha) value at the specified position
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// so that the result of In becomes natural to users.
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//
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// Note that this is not a good manner to use At for logic
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// since color from At might include some errors on some machines.
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// As this is not so important logic, it's ok to use it so far.
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return s.image.At(x-s.x, y-s.y).(color.RGBA).A > 0
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}
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// MoveBy moves the sprite by (x, y).
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func (s *Sprite) MoveBy(x, y int) {
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w, h := s.image.Size()
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s.x += x
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s.y += y
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if s.x < 0 {
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s.x = 0
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}
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if s.x > screenWidth-w {
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s.x = screenWidth - w
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}
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if s.y < 0 {
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s.y = 0
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}
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if s.y > screenHeight-h {
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s.y = screenHeight - h
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}
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}
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// Draw draws the sprite.
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func (s *Sprite) Draw(screen *ebiten.Image, dx, dy int, alpha float64) {
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op := &ebiten.DrawImageOptions{}
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op.GeoM.Translate(float64(s.x+dx), float64(s.y+dy))
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op.ColorM.Scale(1, 1, 1, alpha)
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screen.DrawImage(s.image, op)
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screen.DrawImage(s.image, op)
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}
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// StrokeSource represents a input device to provide strokes.
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type StrokeSource interface {
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Position() (int, int)
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IsJustReleased() bool
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}
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// MouseStrokeSource is a StrokeSource implementation of mouse.
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type MouseStrokeSource struct{}
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func (m *MouseStrokeSource) Position() (int, int) {
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return ebiten.CursorPosition()
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}
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func (m *MouseStrokeSource) IsJustReleased() bool {
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return inpututil.IsMouseButtonJustReleased(ebiten.MouseButtonLeft)
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}
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// TouchStrokeSource is a StrokeSource implementation of touch.
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type TouchStrokeSource struct {
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ID int
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}
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func (t *TouchStrokeSource) Position() (int, int) {
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return ebiten.TouchPosition(t.ID)
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}
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func (t *TouchStrokeSource) IsJustReleased() bool {
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return inpututil.IsTouchJustReleased(t.ID)
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}
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// Stroke manages the current drag state by mouse.
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type Stroke struct {
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source StrokeSource
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// initX and initY represents the position when dragging starts.
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initX int
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initY int
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// currentX and currentY represents the current position
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currentX int
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currentY int
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released bool
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// draggingObject represents a object (sprite in this case)
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// that is being dragged.
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draggingObject interface{}
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}
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func NewStroke(source StrokeSource) *Stroke {
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cx, cy := source.Position()
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return &Stroke{
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source: source,
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initX: cx,
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initY: cy,
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currentX: cx,
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currentY: cy,
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}
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}
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func (s *Stroke) Update() {
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if s.released {
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return
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}
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if s.source.IsJustReleased() {
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s.released = true
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return
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}
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x, y := s.source.Position()
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s.currentX = x
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s.currentY = y
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}
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func (s *Stroke) IsReleased() bool {
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return s.released
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}
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func (s *Stroke) Position() (int, int) {
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return s.currentX, s.currentY
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}
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func (s *Stroke) PositionDiff() (int, int) {
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dx := s.currentX - s.initX
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dy := s.currentY - s.initY
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return dx, dy
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}
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func (s *Stroke) DraggingObject() interface{} {
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return s.draggingObject
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}
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func (s *Stroke) SetDraggingObject(object interface{}) {
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s.draggingObject = object
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}
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type Game struct {
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strokes map[*Stroke]struct{}
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sprites []*Sprite
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}
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var theGame *Game
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func init() {
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// Decode image from a byte slice instead of a file so that
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// this example works in any working directory.
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// If you want to use a file, there are some options:
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// 1) Use os.Open and pass the file to the image decoder.
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// This is a very regular way, but doesn't work on browsers.
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// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
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// This works even on browsers.
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// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
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// This also works on browsers.
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img, _, err := image.Decode(bytes.NewReader(images.Ebiten_png))
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if err != nil {
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log.Fatal(err)
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}
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ebitenImage, _ := ebiten.NewImageFromImage(img, ebiten.FilterDefault)
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// Initialize the sprites.
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sprites := []*Sprite{}
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w, h := ebitenImage.Size()
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for i := 0; i < 50; i++ {
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s := &Sprite{
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image: ebitenImage,
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x: rand.Intn(screenWidth - w),
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y: rand.Intn(screenHeight - h),
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}
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sprites = append(sprites, s)
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}
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// Initialize the game.
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theGame = &Game{
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strokes: map[*Stroke]struct{}{},
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sprites: sprites,
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}
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}
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func (g *Game) spriteAt(x, y int) *Sprite {
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// As the sprites are ordered from back to front,
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// search the clicked/touched sprite in reverse order.
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for i := len(g.sprites) - 1; i >= 0; i-- {
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s := g.sprites[i]
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if s.In(x, y) {
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return s
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}
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}
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return nil
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}
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func (g *Game) updateStroke(stroke *Stroke) {
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stroke.Update()
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if !stroke.IsReleased() {
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return
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}
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s := stroke.DraggingObject().(*Sprite)
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if s == nil {
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return
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}
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s.MoveBy(stroke.PositionDiff())
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index := -1
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for i, ss := range g.sprites {
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if ss == s {
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index = i
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break
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}
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}
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// Move the dragged sprite to the front.
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g.sprites = append(g.sprites[:index], g.sprites[index+1:]...)
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g.sprites = append(g.sprites, s)
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stroke.SetDraggingObject(nil)
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}
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func (g *Game) update(screen *ebiten.Image) error {
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if inpututil.IsMouseButtonJustPressed(ebiten.MouseButtonLeft) {
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s := NewStroke(&MouseStrokeSource{})
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s.SetDraggingObject(g.spriteAt(s.Position()))
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g.strokes[s] = struct{}{}
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}
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for _, id := range inpututil.JustPressedTouchIDs() {
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s := NewStroke(&TouchStrokeSource{id})
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s.SetDraggingObject(g.spriteAt(s.Position()))
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g.strokes[s] = struct{}{}
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}
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for s := range g.strokes {
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g.updateStroke(s)
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if s.IsReleased() {
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delete(g.strokes, s)
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}
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}
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if ebiten.IsRunningSlowly() {
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return nil
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}
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ss := map[*Sprite]*Stroke{}
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for s := range g.strokes {
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ss[s.DraggingObject().(*Sprite)] = s
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}
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for _, s := range g.sprites {
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if stroke, ok := ss[s]; ok {
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dx, dy := stroke.PositionDiff()
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s.Draw(screen, dx, dy, 0.5)
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} else {
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s.Draw(screen, 0, 0, 1)
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}
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}
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ebitenutil.DebugPrint(screen, "Drag & Drop the sprites!")
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return nil
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}
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func main() {
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if err := ebiten.Run(theGame.update, screenWidth, screenHeight, 2, "Drag & Drop (Ebiten Demo)"); err != nil {
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log.Fatal(err)
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}
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}
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