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@@ -0,0 +1,112 @@
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+const SMALLEST_SIZE = 4.0;
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+const LARGEST_SIZE = 48.0;
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+
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+const DEFAULT_SIZE = 24.0;
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+
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+class State {
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+ updateWindowSize(w, h) {
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+ this.w = w;
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+ this.h = h;
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+ this.canvas.width = w;
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+ this.canvas.height = h;
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+ this.data = {};
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+ }
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+
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+ constructor(canvas, ctx, w, h) {
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+ this.canvas = canvas;
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+ this.ctx = ctx;
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+ this.updateWindowSize(w, h);
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+ this.size = DEFAULT_SIZE;
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+ this.mode = 'square';
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+ }
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+
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+ scroll(delta) {
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+ this.size += delta / 30.0;
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+ if (this.size < SMALLEST_SIZE) {
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+ this.size = SMALLEST_SIZE;
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+ } else if (this.size > LARGEST_SIZE) {
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+ this.size = LARGEST_SIZE;
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+ }
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+ }
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+
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+ draw(mouseLoc) {
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+ this.ctx.clearRect(0, 0, this.w, this.h);
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+
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+ if (mouseLoc !== null) {
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+ let [fx, fy] = mouseLoc;
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+ this.ctx.fillStyle = '#f00';
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+
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+ if (this.mode === 'square') {
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+ fx = Math.floor(fx / this.size);
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+ fy = Math.floor(fy / this.size);
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+ this.ctx.fillRect(fx * this.size, fy * this.size, this.size, this.size);
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+ } else {
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+ this.ctx.strokeStyle = '#f00';
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+ const half = this.size / 2
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+ fx = Math.floor((fx + half) / this.size);
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+ fy = Math.floor((fy + half) / this.size);
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+ this.ctx.moveTo(fx * this.size, fy * this.size);
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+ this.ctx.arc(fx * this.size, fy * this.size, 5, 0, Math.PI * 2, true);
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+ this.ctx.stroke();
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+ }
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+ }
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+
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+ this.ctx.strokeStyle = '#000';
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+ for (let x = 0; Math.floor(x / this.size < this.w); x++) {
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+ this.ctx.beginPath();
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+ this.ctx.moveTo(x * this.size, 0);
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+ this.ctx.lineTo(x * this.size, this.h);
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+ this.ctx.stroke();
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+ }
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+
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+ for (let y = 0; Math.floor(y / this.size < this.h); y++) {
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+ this.ctx.beginPath();
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+ this.ctx.moveTo(0, y * this.size);
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+ this.ctx.lineTo(this.w, y * this.size);
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+ this.ctx.stroke();
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+ }
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+ }
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+}
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+
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+let main = () => {
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+ const canvas = document.getElementById('cv');
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+
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+ const w = window.innerWidth;
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+ const h = window.innerHeight;
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+
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+ const ctx = canvas.getContext('2d');
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+
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+ let state = new State(canvas, ctx, w, h);
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+ let last_mouse = null;
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+ state.draw(last_mouse);
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+
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+ document.addEventListener('mousemove', e => {
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+ last_mouse = [e.clientX, e.clientY];
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+ state.draw(last_mouse);
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+ });
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+
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+ document.addEventListener('wheel', e => {
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+ state.scroll(-e.deltaY);
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+ state.draw(last_mouse);
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+ });
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+
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+ window.addEventListener('resize', () => {
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+ state.updateWindowSize(
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+ window.innerWidth,
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+ window.innerHeight,
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+ );
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+ state.draw(last_mouse);
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+ });
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+
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+ document.addEventListener('keydown', e => {
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+ if (e.key === ' ') {
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+ if (state.mode === 'square')
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+ state.mode = 'dot';
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+ else
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+ state.mode = 'square';
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+ }
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+ state.draw(last_mouse);
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+ });
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+};
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+
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+window.onload = main;
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