From 665ef460648ca312e81b79a7b110e16f63153e54 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Tue, 13 Jan 2015 23:03:37 +0900
Subject: [PATCH] Add example/sprites (#83)

---
 example/sprites/main.go                      | 131 +++++++++++++++++++
 internal/graphics/internal/shader/draw.go    |   6 +
 internal/graphics/internal/shader/program.go |   9 +-
 3 files changed, 142 insertions(+), 4 deletions(-)
 create mode 100644 example/sprites/main.go

diff --git a/example/sprites/main.go b/example/sprites/main.go
new file mode 100644
index 000000000..e2b4b6916
--- /dev/null
+++ b/example/sprites/main.go
@@ -0,0 +1,131 @@
+// Copyright 2015 Hajime Hoshi
+//
+// 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.
+
+package main
+
+import (
+	"fmt"
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+	_ "image/png"
+	"log"
+	"math/rand"
+)
+
+const (
+	screenWidth  = 320
+	screenHeight = 240
+)
+
+var (
+	ebitenImage *ebiten.Image
+)
+
+type Sprite struct {
+	image *ebiten.Image
+	x     int
+	y     int
+	vx    int
+	vy    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
+	}
+	if s.y < 0 {
+		s.y = -s.y
+		s.vy = -s.vy
+	}
+	w, h := s.image.Size()
+	if screenWidth <= s.x+w {
+		s.x = 2*(screenWidth-w) - s.x
+		s.vx = -s.vx
+	}
+	if screenHeight <= s.y+h {
+		s.y = 2*(screenHeight-h) - s.y
+		s.vy = -s.vy
+	}
+}
+
+func (s *Sprite) Dst() (x0, y0, x1, y1 int) {
+	w, h := s.image.Size()
+	return s.x, s.y, s.x + w, s.y + h
+}
+
+func (s *Sprite) Src() (x0, y0, x1, y1 int) {
+	w, h := s.image.Size()
+	return 0, 0, w, h
+}
+
+type Sprites []*Sprite
+
+func (s Sprites) Update() {
+	for _, sprite := range s {
+		sprite.Update()
+	}
+}
+
+func (s Sprites) Len() int {
+	return len(s)
+}
+
+func (s Sprites) Dst(i int) (x0, y0, x1, y1 int) {
+	return s[i].Dst()
+}
+
+func (s Sprites) Src(i int) (x0, y0, x1, y1 int) {
+	return s[i].Src()
+}
+
+var sprites = make(Sprites, 2500)
+
+func update(screen *ebiten.Image) error {
+	sprites.Update()
+	op := &ebiten.DrawImageOptions{
+		ImageParts: sprites,
+	}
+	op.ColorM.Scale(1.0, 1.0, 1.0, 0.5)
+	if err := screen.DrawImage(ebitenImage, op); err != nil {
+		return err
+	}
+	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f\nNum of sprites: %d", ebiten.CurrentFPS(), sprites.Len()))
+	return nil
+}
+
+func main() {
+	var err error
+	ebitenImage, _, err = ebitenutil.NewImageFromFile("images/ebiten.png", ebiten.FilterNearest)
+	if err != nil {
+		log.Fatal(err)
+	}
+	for i, _ := range 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
+		sprites[i] = &Sprite{
+			image: ebitenImage,
+			x:     x,
+			y:     y,
+			vx:    vx,
+			vy:    vy,
+		}
+	}
+	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Sprites (Ebiten Demo)"); err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/internal/graphics/internal/shader/draw.go b/internal/graphics/internal/shader/draw.go
index a50d47872..2673aecfb 100644
--- a/internal/graphics/internal/shader/draw.go
+++ b/internal/graphics/internal/shader/draw.go
@@ -15,6 +15,8 @@
 package shader
 
 import (
+	"errors"
+	"fmt"
 	"github.com/hajimehoshi/ebiten/internal/opengl"
 )
 
@@ -56,6 +58,10 @@ func DrawTexture(c *opengl.Context, texture opengl.Texture, projectionMatrix *[4
 	if quads.Len() == 0 {
 		return nil
 	}
+	// TODO: Change this panic if image.DrawImage allows more than quadsMaxNum parts.
+	if quadsMaxNum < quads.Len() {
+		return errors.New(fmt.Sprintf("len(quads) must be equal to or less than %d", quadsMaxNum))
+	}
 
 	f := useProgramTexture(c, glMatrix(projectionMatrix), texture, geo, color)
 	defer f.FinishProgram()
diff --git a/internal/graphics/internal/shader/program.go b/internal/graphics/internal/shader/program.go
index 268753b98..2fd343895 100644
--- a/internal/graphics/internal/shader/program.go
+++ b/internal/graphics/internal/shader/program.go
@@ -23,8 +23,9 @@ var (
 	programRect    opengl.Program
 )
 
+const quadsMaxNum = 10000
+
 func initialize(c *opengl.Context) error {
-	const size = 10000
 	const uint16Size = 2
 
 	shaderVertexNative, err := c.NewShader(c.VertexShader, shader(c, shaderVertex))
@@ -62,10 +63,10 @@ func initialize(c *opengl.Context) error {
 	}
 
 	const stride = 4 * 4
-	c.NewBuffer(c.ArrayBuffer, stride*size, c.DynamicDraw)
+	c.NewBuffer(c.ArrayBuffer, stride*quadsMaxNum, c.DynamicDraw)
 
-	indices := make([]uint16, 6*size)
-	for i := uint16(0); i < size; i++ {
+	indices := make([]uint16, 6*quadsMaxNum)
+	for i := uint16(0); i < quadsMaxNum; i++ {
 		indices[6*i+0] = 4*i + 0
 		indices[6*i+1] = 4*i + 1
 		indices[6*i+2] = 4*i + 2