From e6143d0a2b96ab73807070d4b017498f9476be2b Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Fri, 23 Feb 2018 02:51:43 +0900
Subject: [PATCH] examples: Add spriteshd

---
 examples/spriteshd/main.go | 179 +++++++++++++++++++++++++++++++++++++
 1 file changed, 179 insertions(+)
 create mode 100644 examples/spriteshd/main.go

diff --git a/examples/spriteshd/main.go b/examples/spriteshd/main.go
new file mode 100644
index 000000000..9ffb7f578
--- /dev/null
+++ b/examples/spriteshd/main.go
@@ -0,0 +1,179 @@
+// Copyright 2018 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build example
+
+package main
+
+import (
+	"errors"
+	"fmt"
+	_ "image/png"
+	"log"
+	"math"
+	"math/rand"
+
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+	"github.com/hajimehoshi/ebiten/inpututil"
+)
+
+const (
+	screenWidth  = 1920
+	screenHeight = 1080
+	maxAngle     = 256
+)
+
+var (
+	ebitenImage *ebiten.Image
+)
+
+type Sprite struct {
+	imageWidth  int
+	imageHeight int
+	x           int
+	y           int
+	vx          int
+	vy          int
+	angle       int
+}
+
+func (s *Sprite) Update() {
+	s.x += s.vx
+	s.y += s.vy
+	if s.x < 0 {
+		s.x = -s.x
+		s.vx = -s.vx
+	} else if screenWidth <= s.x+s.imageWidth {
+		s.x = 2*(screenWidth-s.imageWidth) - s.x
+		s.vx = -s.vx
+	}
+	if s.y < 0 {
+		s.y = -s.y
+		s.vy = -s.vy
+	} else if screenHeight <= s.y+s.imageHeight {
+		s.y = 2*(screenHeight-s.imageHeight) - s.y
+		s.vy = -s.vy
+	}
+	s.angle++
+	s.angle %= maxAngle
+}
+
+type Sprites struct {
+	sprites []*Sprite
+	num     int
+}
+
+func (s *Sprites) Update() {
+	for _, sprite := range s.sprites {
+		sprite.Update()
+	}
+}
+
+const (
+	MinSprites = 0
+	MaxSprites = 50000
+)
+
+var (
+	sprites = &Sprites{make([]*Sprite, MaxSprites), 500}
+	op      = &ebiten.DrawImageOptions{}
+)
+
+func init() {
+	img, _, err := ebitenutil.NewImageFromFile("_resources/images/ebiten.png", ebiten.FilterDefault)
+	if err != nil {
+		log.Fatal(err)
+	}
+	w, h := img.Size()
+	ebitenImage, _ = ebiten.NewImage(w, h, ebiten.FilterDefault)
+	op := &ebiten.DrawImageOptions{}
+	op.ColorM.Scale(1, 1, 1, 0.5)
+	ebitenImage.DrawImage(img, op)
+	for i := range sprites.sprites {
+		w, h := ebitenImage.Size()
+		x, y := rand.Intn(screenWidth-w), rand.Intn(screenHeight-h)
+		vx, vy := 2*rand.Intn(2)-1, 2*rand.Intn(2)-1
+		a := rand.Intn(maxAngle)
+		sprites.sprites[i] = &Sprite{
+			imageWidth:  w,
+			imageHeight: h,
+			x:           x,
+			y:           y,
+			vx:          vx,
+			vy:          vy,
+			angle:       a,
+		}
+	}
+}
+
+var regularTermination = errors.New("regular termination")
+
+func update(screen *ebiten.Image) error {
+	if inpututil.IsKeyJustPressed(ebiten.KeyQ) {
+		return regularTermination
+	}
+
+	// Decrease the nubmer of the sprites.
+	if ebiten.IsKeyPressed(ebiten.KeyLeft) {
+		sprites.num -= 20
+		if sprites.num < MinSprites {
+			sprites.num = MinSprites
+		}
+	}
+
+	// Increase the nubmer of the sprites.
+	if ebiten.IsKeyPressed(ebiten.KeyRight) {
+		sprites.num += 20
+		if MaxSprites < sprites.num {
+			sprites.num = MaxSprites
+		}
+	}
+
+	sprites.Update()
+
+	if ebiten.IsRunningSlowly() {
+		return nil
+	}
+
+	// Draw each sprite.
+	// DrawImage can be called many many times, but in the implementation,
+	// the actual draw call to GPU is very few since these calls satisfy
+	// some conditions e.g. all the rendering sources and targets are same.
+	// For more detail, see:
+	// https://godoc.org/github.com/hajimehoshi/ebiten#Image.DrawImage
+	w, h := ebitenImage.Size()
+	for i := 0; i < sprites.num; i++ {
+		s := sprites.sprites[i]
+		op.GeoM.Reset()
+		op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
+		op.GeoM.Rotate(2 * math.Pi * float64(s.angle) / maxAngle)
+		op.GeoM.Translate(float64(w)/2, float64(h)/2)
+		op.GeoM.Translate(float64(s.x), float64(s.y))
+		screen.DrawImage(ebitenImage, op)
+	}
+	msg := fmt.Sprintf(`FPS: %0.2f
+Num of sprites: %d
+Press <- or -> to change the number of sprites
+Press Q to quit`, ebiten.CurrentFPS(), sprites.num)
+	ebitenutil.DebugPrint(screen, msg)
+	return nil
+}
+
+func main() {
+	ebiten.SetFullscreen(true)
+	if err := ebiten.Run(update, screenWidth, screenHeight, 1, "Sprites HD (Ebiten Demo)"); err != nil && err != regularTermination {
+		log.Fatal(err)
+	}
+}