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Fireworks.dart
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Fireworks.dart
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// a Dart port of http://jsdo.it/zarkswerk/fireworx
// Author: Fuji, Goro (gfx) <gfuji@cpan.org>
// LICENSE: The MIT License
#import('dart:html');
final num quantity = 360;
final num size = 2.0;
final num decay = 0.98;
final num gravity = 2.0;
final num speed = 6.0;
class Random { // drand48
static num x = 0;
static num next() {
x = x * 0x5DEECE66D + 0xB;
x %= 0xFFFFFFFFFFFF;
return x * (1.0/(0xFFFFFFFFFFFF+1));
}
}
num random() => Random.next();
String randomColor() {
final List<int> rgb = new List<int>(3);
for(int i = 0; i < rgb.length; ++i) {
rgb[i] = (random() * 0xFF + 60).toInt();
}
return "rgb(${rgb[0]},${rgb[1]},${rgb[2]})";
}
class Spark {
static final num rad = Math.PI * 2;
num posX;
num posY;
num velX;
num velY;
num size;
Spark(this.posX, this.posY, this.size) {
num angle = random() * rad;
num velocity = random() * speed;
velX = Math.cos(angle) * velocity;
velY = Math.sin(angle) * velocity;
}
bool draw(FireworkView view, String color) {
posX += velX;
posY += velY;
velX *= decay;
velY *= decay;
size *= decay;
posY += gravity;
view.cx.beginPath();
view.cx.arc(posX, posY, size, 0, rad, true);
view.cx.fillStyle = color;
view.cx.fill();
// returns true if it dismissed
if(size <= 0.1) return true;
if(posX <= 0 || posY <= 0) return true;
if(posX >= view.width || posY >= view.height) return true;
return false;
}
}
class Firework {
final String color;
final List<Spark> sparks;
final FireworkView view;
Firework(this.view, int x, int y) : color = randomColor(), sparks = new List<Spark>() {
for(int i = 0; i < quantity; ++i) {
sparks.add(new Spark(x, y, size));
}
}
void update(CanvasRenderingContext2D cx) {
for(int i = 0; i < sparks.length; ++i) {
Spark s = sparks[i];
if(s.draw(this.view, color)) {
sparks.removeRange(i, 1);
}
}
}
bool dismissed() => sparks.isEmpty();
}
class FireworkView {
CanvasRenderingContext2D cx;
int width;
int height;
int left;
int top;
List<Firework> fireworks;
int numSparks = 0;
FireworkView(CanvasElement canvas) : fireworks = new List<Firework>() {
cx = canvas.getContext("2d");
width = canvas.width;
height = canvas.height;
canvas.rect.then((ElementRect rect) {
left = rect.bounding.left;
top = rect.bounding.top;
canvas.on.mouseDown.add( (MouseEvent e) {
explode(e.clientX, e.clientY);
});
canvas.on.touchStart.add( (TouchEvent e) {
explode(e.touches[0].pageX, e.touches[1].pageY);
});
// for benchmarking
for(int i = 0; i < 3; i++) {
explode( random() * canvas.width, (canvas.height / 4).toInt());
}
});
}
void explode(int x, int y) {
fireworks.add(new Firework(this, x - left, y - top));
}
void update() {
if(fireworks.isEmpty()) return;
numSparks = 0;
for(int i = 0; i < fireworks.length; ++i) {
Firework fw = fireworks[i];
fw.update(cx);
if(fw.dismissed()) {
fireworks.removeRange(i, 1);
}
else {
numSparks += fw.sparks.length;
}
}
cx.fillStyle = "rgba(0, 0, 0, 0.3)";
cx.fillRect(0, 0, width, height);
}
}
class FPSWatcher {
Stopwatch watch;
int fps;
FPSWatcher() {
watch = new Stopwatch.start();
fps = 0;
}
void update(int numSparks) {
++fps;
if(watch.elapsedInMs() >= 1000) {
String message = "FPS: $fps (sparks: $numSparks)";
document.query('#fps').innerHTML = message;
if(numSparks > 0) print(message);
watch.reset();
fps = 0;
}
}
}
void main() {
CanvasElement canvas = document.query("#night-sky");
FireworkView view = new FireworkView(canvas);
FPSWatcher watcher = new FPSWatcher();
window.setInterval(() {
view.update();
watcher.update(view.numSparks);
}, 0);
}