code-boxx/0-JS-DRAW.MD

## 0-JS-DRAW.MD

      
    Raw
  

              0-JS-DRAW.MD
            
          
    JAVASCRIPT DRAWING PWA

https://code-boxx.com/javascript-drawing-app/
IMAGES


LICENSE

Copyright by Code Boxx
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

  
## 1-draw.html
<!DOCTYPE html>
<html lang="en">
<head>
  <!-- TITLE + CHARSET + DESCRIPTION + VIEWPORT + FAVICON -->
  <title>JavaScript Drawing App</title>
  <meta charset="utf-8">
  <meta name="description" content="Offline Javascript Drawing App">
  <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.5">
  <link rel="icon" href="favicon.png" type="image/png">

  <!-- ANDROID + CHROME + APPLE + WINDOWS APP -->
  <meta name="mobile-web-app-capable" content="yes">
  <meta name="theme-color" content="white">
  <link rel="apple-touch-icon" href="icon-512.png">
  <meta name="apple-mobile-web-app-capable" content="yes">
  <meta name="apple-mobile-web-app-status-bar-style" content="black">
  <meta name="apple-mobile-web-app-title" content="JS Draw">
  <meta name="msapplication-TileImage" content="icon-512.png">
  <meta name="msapplication-TileColor" content="#ffffff">

  <!-- WEB APP MANIFEST -->
  <!-- https://web.dev/add-manifest/ -->
  <link rel="manifest" href="3a-manifest.json">

  <!-- SERVICE WORKER -->
  <script>
  if ("serviceWorker" in navigator) {
    navigator.serviceWorker.register("3b-worker.js");
  }
  </script>

  <!-- STYLESHEET + JAVASCRIPT -->
  <link rel="stylesheet" href="2-draw.css">
  <script src="2-draw.js"></script>
</head>
<body>
  <div id="wrapper">
    <!-- (A) CANVAS -->
    <canvas id="canvas"></canvas>
    <!-- (B) DRAW CONTROLS -->
    <div id="controls">
      <input type="button" value="Clear" id="cClear">
      <input type="color" id="cColor">
      <input type="number" min="1" max="9" value="1" id="cSize">
      <a id="cSave" download="draw.jpg">Save</a>
    </div>
  </div>
</body>
</html>

## 2-draw.css
/* (A) WHOLE SITE */
* {
  font-family: Arial, Helvetica, sans-serif;
  box-sizing: border-box;
}

/* (B) WRAPPER */
#wrapper {
  width: 600px;
  margin: 0 auto;
}

/* (C) CANVAS */
#canvas {
  width: 600px;
  height: 400px;
  border: 1px solid black;
}

/* (D) CONTROLS */
#controls {
  display: flex;
  border: 1px solid #aaa;
}
#controls * {
  height: 50px;
  padding: 10px;
  border: 0;
}
#cClear, #cColor, #cSave { cursor: pointer; }
#cColor { flex-grow: 1; }
#cClear {
  color: #fff;
  background: #c51c1c;
}
#cSave {
  display: flex;
  color: #fff;
  background: #4e74cb;
  align-items: center;
  justify-content: center;
}

## 2-draw.js
// CREDITS
// https://dev.to/0shuvo0/lets-create-a-drawing-app-with-js-4ej3
// https://riptutorial.com/html5-canvas/example/11659/detecting-mouse-position-on-the-canvas

var draw = {
  // (A) PROPERTIES
  canvas : null, // html canvas
  ctx : null, // html canvas context
  px: null, py : null, // previous mouse coordinates
  cx: null, cy : null, // current mouse coordinates
  go : false, // flag to control paint

  // (B) INIT
  init : () => {
    // (B1) GET HTML ELEMENTS
    draw.canvas = document.getElementById("canvas");
    draw.ctx = draw.canvas.getContext("2d");

    // (B2) SET CANVAS WIDTH & HEIGHT
    draw.canvas.width = draw.canvas.offsetWidth;
    draw.canvas.height = draw.canvas.offsetHeight;

    // (B3) DEFAULT DRAW SETTINGS
    draw.ctx.fillStyle = "#ffffff";
    draw.ctx.strokeStyle = "#000000";
    draw.ctx.lineWidth = 1;
    draw.ctx.fillRect(0, 0, draw.canvas.width, draw.canvas.height);

    // (B4) ATTACH DRAW CONTROLS
    // (B4-1) CLEAR CANVAS
    document.getElementById("cClear").onclick = () => draw.ctx.fillRect(0, 0, draw.canvas.width, draw.canvas.height);

    // (B4-2) DRAW COLOR
    document.getElementById("cColor").onchange = e => draw.ctx.strokeStyle = e.target.value;

    // (B4-3) DRAW SIZE
    document.getElementById("cSize").onchange = e => draw.ctx.lineWidth = e.target.value;

    // (B4-4) SAVE CANVAS
    document.getElementById("cSave").onclick = e => e.target.href = draw.canvas.toDataURL("image/jpg");

    // (B5) ENGAGE/DISENGAGE PAINT
    let disengage = () => { draw.px = null; draw.py = null; draw.go = false; };
    draw.canvas.addEventListener("mousedown", e => draw.go = true);
    draw.canvas.addEventListener("mouseup", disengage);
    draw.canvas.addEventListener("mouseout", disengage);
    draw.canvas.addEventListener("mousemove", draw.paint);
  },

  // (C) PAINT
  paint : e => { if (draw.go) {
    // (C1) GET CANVAS MOUSE COORDINATES
    let cRect = draw.canvas.getBoundingClientRect();
    draw.cx = Math.round(e.clientX - cRect.left);
    draw.cy = Math.round(e.clientY - cRect.top);

    // (C2) SET INITIAL COORDINATES
    if (draw.px == null || draw.py == null) {
      draw.px = draw.cx;
      draw.py = draw.cy;
    }

    // (C3) DRAW
    draw.ctx.beginPath();
    draw.ctx.moveTo(draw.px, draw.py);
    draw.ctx.lineTo(draw.cx, draw.cy);
    draw.ctx.stroke();

    // (C4) UPDATE COORDINATES
    draw.px = draw.cx;
    draw.py = draw.cy;
  }}
};
window.onload = draw.init;

## 3a-manifest.json
{
  "short_name": "Draw",
  "name": "JS Draw",
  "icons": [{
    "src": "favicon.png",
    "sizes": "64x64",
    "type": "image/png"
  }, {
    "src": "icon-512.png",
    "sizes": "512x512",
    "type": "image/png"
  }],
  "start_url": "1-draw.html",
  "scope": "/",
  "background_color": "white",
  "theme_color": "white",
  "display": "standalone"
}

## 3b-worker.js
// (A) CREATE/INSTALL CACHE
self.addEventListener("install", evt => {
  self.skipWaiting();
  evt.waitUntil(
    caches.open("JSDraw")
    .then(cache => cache.addAll([
      "1-draw.html",
      "2-draw.css",
      "2-draw.js",
      "favicon.png",
      "icon-512.png"
    ]))
    .catch(err => console.error(err))
  );
});

// (B) CLAIM CONTROL INSTANTLY
self.addEventListener("activate", evt => self.clients.claim());

// (C) LOAD FROM CACHE FIRST, FALLBACK TO NETWORK IF NOT FOUND
self.addEventListener("fetch", evt => evt.respondWith(
  caches.match(evt.request).then(res => res || fetch(evt.request))
));
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<!-- TITLE + CHARSET + DESCRIPTION + VIEWPORT + FAVICON -->
	<title>JavaScript Drawing App</title>
	<meta charset="utf-8">
	<meta name="description" content="Offline Javascript Drawing App">
	<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.5">
	<link rel="icon" href="favicon.png" type="image/png">

	<!-- ANDROID + CHROME + APPLE + WINDOWS APP -->
	<meta name="mobile-web-app-capable" content="yes">
	<meta name="theme-color" content="white">
	<link rel="apple-touch-icon" href="icon-512.png">
	<meta name="apple-mobile-web-app-capable" content="yes">
	<meta name="apple-mobile-web-app-status-bar-style" content="black">
	<meta name="apple-mobile-web-app-title" content="JS Draw">
	<meta name="msapplication-TileImage" content="icon-512.png">
	<meta name="msapplication-TileColor" content="#ffffff">

	<!-- WEB APP MANIFEST -->
	<!-- https://web.dev/add-manifest/ -->
	<link rel="manifest" href="3a-manifest.json">

	<!-- SERVICE WORKER -->
	<script>
	if ("serviceWorker" in navigator) {
	navigator.serviceWorker.register("3b-worker.js");
	}
	</script>

	<!-- STYLESHEET + JAVASCRIPT -->
	<link rel="stylesheet" href="2-draw.css">
	<script src="2-draw.js"></script>
	</head>
	<body>
	<div id="wrapper">
	<!-- (A) CANVAS -->
	<canvas id="canvas"></canvas>
	<!-- (B) DRAW CONTROLS -->
	<div id="controls">
	<input type="button" value="Clear" id="cClear">
	<input type="color" id="cColor">
	<input type="number" min="1" max="9" value="1" id="cSize">
	<a id="cSave" download="draw.jpg">Save</a>
	</div>
	</div>
	</body>
	</html>
	/* (A) WHOLE SITE */
	* {
	font-family: Arial, Helvetica, sans-serif;
	box-sizing: border-box;
	}

	/* (B) WRAPPER */
	#wrapper {
	width: 600px;
	margin: 0 auto;
	}

	/* (C) CANVAS */
	#canvas {
	width: 600px;
	height: 400px;
	border: 1px solid black;
	}

	/* (D) CONTROLS */
	#controls {
	display: flex;
	border: 1px solid #aaa;
	}
	#controls * {
	height: 50px;
	padding: 10px;
	border: 0;
	}
	#cClear, #cColor, #cSave { cursor: pointer; }
	#cColor { flex-grow: 1; }
	#cClear {
	color: #fff;
	background: #c51c1c;
	}
	#cSave {
	display: flex;
	color: #fff;
	background: #4e74cb;
	align-items: center;
	justify-content: center;
	}
	// CREDITS
	// https://dev.to/0shuvo0/lets-create-a-drawing-app-with-js-4ej3
	// https://riptutorial.com/html5-canvas/example/11659/detecting-mouse-position-on-the-canvas

	var draw = {
	// (A) PROPERTIES
	canvas : null, // html canvas
	ctx : null, // html canvas context
	px: null, py : null, // previous mouse coordinates
	cx: null, cy : null, // current mouse coordinates
	go : false, // flag to control paint

	// (B) INIT
	init : () => {
	// (B1) GET HTML ELEMENTS
	draw.canvas = document.getElementById("canvas");
	draw.ctx = draw.canvas.getContext("2d");

	// (B2) SET CANVAS WIDTH & HEIGHT
	draw.canvas.width = draw.canvas.offsetWidth;
	draw.canvas.height = draw.canvas.offsetHeight;

	// (B3) DEFAULT DRAW SETTINGS
	draw.ctx.fillStyle = "#ffffff";
	draw.ctx.strokeStyle = "#000000";
	draw.ctx.lineWidth = 1;
	draw.ctx.fillRect(0, 0, draw.canvas.width, draw.canvas.height);

	// (B4) ATTACH DRAW CONTROLS
	// (B4-1) CLEAR CANVAS
	document.getElementById("cClear").onclick = () => draw.ctx.fillRect(0, 0, draw.canvas.width, draw.canvas.height);

	// (B4-2) DRAW COLOR
	document.getElementById("cColor").onchange = e => draw.ctx.strokeStyle = e.target.value;

	// (B4-3) DRAW SIZE
	document.getElementById("cSize").onchange = e => draw.ctx.lineWidth = e.target.value;

	// (B4-4) SAVE CANVAS
	document.getElementById("cSave").onclick = e => e.target.href = draw.canvas.toDataURL("image/jpg");

	// (B5) ENGAGE/DISENGAGE PAINT
	let disengage = () => { draw.px = null; draw.py = null; draw.go = false; };
	draw.canvas.addEventListener("mousedown", e => draw.go = true);
	draw.canvas.addEventListener("mouseup", disengage);
	draw.canvas.addEventListener("mouseout", disengage);
	draw.canvas.addEventListener("mousemove", draw.paint);
	},

	// (C) PAINT
	paint : e => { if (draw.go) {
	// (C1) GET CANVAS MOUSE COORDINATES
	let cRect = draw.canvas.getBoundingClientRect();
	draw.cx = Math.round(e.clientX - cRect.left);
	draw.cy = Math.round(e.clientY - cRect.top);

	// (C2) SET INITIAL COORDINATES
	if (draw.px == null \|\| draw.py == null) {
	draw.px = draw.cx;
	draw.py = draw.cy;
	}

	// (C3) DRAW
	draw.ctx.beginPath();
	draw.ctx.moveTo(draw.px, draw.py);
	draw.ctx.lineTo(draw.cx, draw.cy);
	draw.ctx.stroke();

	// (C4) UPDATE COORDINATES
	draw.px = draw.cx;
	draw.py = draw.cy;
	}}
	};
	window.onload = draw.init;
	{
	"short_name": "Draw",
	"name": "JS Draw",
	"icons": [{
	"src": "favicon.png",
	"sizes": "64x64",
	"type": "image/png"
	}, {
	"src": "icon-512.png",
	"sizes": "512x512",
	"type": "image/png"
	}],
	"start_url": "1-draw.html",
	"scope": "/",
	"background_color": "white",
	"theme_color": "white",
	"display": "standalone"
	}
	// (A) CREATE/INSTALL CACHE
	self.addEventListener("install", evt => {
	self.skipWaiting();
	evt.waitUntil(
	caches.open("JSDraw")
	.then(cache => cache.addAll([
	"1-draw.html",
	"2-draw.css",
	"2-draw.js",
	"favicon.png",
	"icon-512.png"
	]))
	.catch(err => console.error(err))
	);
	});

	// (B) CLAIM CONTROL INSTANTLY
	self.addEventListener("activate", evt => self.clients.claim());

	// (C) LOAD FROM CACHE FIRST, FALLBACK TO NETWORK IF NOT FOUND
	self.addEventListener("fetch", evt => evt.respondWith(
	caches.match(evt.request).then(res => res \|\| fetch(evt.request))
	));