'Trying to make this script work with touchscreen
i got this code looking around this forum but, I'm not being able to make it work on mobile devices with touchscreen. Problem is I need it to work as simple as this, not calling any library, because it's not for an app but for a simple Wordpress that's using an html widget. Is this even posible?
Thank you all!
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="400" height="200" style="background: #ffffff; margin-left: 0px;">Your browser does not support the HTML5 canvas tag.</canvas>
<script>
const c = document.getElementById("myCanvas");
// c.addEventListener("click", penTool); // fires after mouse left btn is released
c.addEventListener("mousedown", setLastCoords); // fires before mouse left btn is released
c.addEventListener("mousemove", freeForm);
const ctx = c.getContext("2d");
function setLastCoords(e) {
const {x, y} = c.getBoundingClientRect();
lastX = e.clientX - x;
lastY = e.clientY - y;
}
function freeForm(e) {
if (e.buttons !== 1) return; // left button is not pushed yet
penTool(e);
}
function penTool(e) {
const {x, y} = c.getBoundingClientRect();
const newX = e.clientX - x;
const newY = e.clientY - y;
ctx.beginPath();
ctx.lineWidth = 5;
ctx.moveTo(lastX, lastY);
ctx.lineTo(newX, newY);
ctx.strokeStyle = 'black';
ctx.stroke();
ctx.closePath();
lastX = newX;
lastY = newY;
}
let lastX = 0;
let lastY = 0;
</script>
</body>
</html>
Came up with this for mobile version only, still not working :(
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="400" height="200" style="background: #ffffff; margin-left: 0px;">Your browser does not support the HTML5 canvas tag.</canvas>
<script>
const c = document.getElementById("myCanvas");
// c.addEventListener("click", penTool); // fires after mouse left btn is released
c.addEventListener("touchstart", setLastCoords); // fires before mouse left btn is released
c.addEventListener("touchmove", freeForm);
const ctx = c.getContext("2d");
function setLastCoords(e) {
const {x, y} = c.getBoundingClientRect();
lastX = e.touches[0].clientX - x;
lastY = e.touches[0].clientY - y;
}
function freeForm(e) {
if (e.touches !== 1) return; // left button is not pushed yet
penTool(e);
}
function penTool(e) {
const {x, y} = c.getBoundingClientRect();
const newX = e.touches[0].clientX;
const newY = e.touches[0].clientY;
ctx.beginPath();
ctx.lineWidth = 5;
ctx.moveTo(lastX, lastY);
ctx.lineTo(newX, newY);
ctx.strokeStyle = 'black';
ctx.stroke();
ctx.closePath();
lastX = newX;
lastY = newY;
}
let lastX = 0;
let lastY = 0;
</script>
</body>
</html>I also tried this script (credits to Zipso, great article on that)
<head>
<title>Sketchpad</title>
<script type="text/javascript">
// Variables for referencing the canvas and 2dcanvas context
var canvas,ctx;
// Variables to keep track of the mouse position and left-button status
var mouseX,mouseY,mouseDown=0;
// Variables to keep track of the touch position
var touchX,touchY;
// Keep track of the old/last position when drawing a line
// We set it to -1 at the start to indicate that we don't have a good value for it yet
var lastX,lastY=-1;
// Draws a line between the specified position on the supplied canvas name
// Parameters are: A canvas context, the x position, the y position, the size of the dot
function drawLine(ctx,x,y,size) {
// If lastX is not set, set lastX and lastY to the current position
if (lastX==-1) {
lastX=x;
lastY=y;
}
// Let's use black by setting RGB values to 0, and 255 alpha (completely opaque)
r=0; g=0; b=0; a=255;
// Select a fill style
ctx.strokeStyle = "rgba("+r+","+g+","+b+","+(a/255)+")";
// Set the line "cap" style to round, so lines at different angles can join into each other
ctx.lineCap = "round";
//ctx.lineJoin = "round";
// Draw a filled line
ctx.beginPath();
// First, move to the old (previous) position
ctx.moveTo(lastX,lastY);
// Now draw a line to the current touch/pointer position
ctx.lineTo(x,y);
// Set the line thickness and draw the line
ctx.lineWidth = size;
ctx.stroke();
ctx.closePath();
// Update the last position to reference the current position
lastX=x;
lastY=y;
}
// Clear the canvas context using the canvas width and height
function clearCanvas(canvas,ctx) {
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
// Keep track of the mouse button being pressed and draw a dot at current location
function sketchpad_mouseDown() {
mouseDown=1;
drawLine(ctx,mouseX,mouseY,12);
}
// Keep track of the mouse button being released
function sketchpad_mouseUp() {
mouseDown=0;
// Reset lastX and lastY to -1 to indicate that they are now invalid, since we have lifted the "pen"
lastX=-1;
lastY=-1;
}
// Keep track of the mouse position and draw a dot if mouse button is currently pressed
function sketchpad_mouseMove(e) {
// Update the mouse co-ordinates when moved
getMousePos(e);
// Draw a dot if the mouse button is currently being pressed
if (mouseDown==1) {
drawLine(ctx,mouseX,mouseY,12);
}
}
// Get the current mouse position relative to the top-left of the canvas
function getMousePos(e) {
if (!e)
var e = event;
if (e.offsetX) {
mouseX = e.offsetX;
mouseY = e.offsetY;
}
else if (e.layerX) {
mouseX = e.layerX;
mouseY = e.layerY;
}
}
// Draw something when a touch start is detected
function sketchpad_touchStart() {
// Update the touch co-ordinates
getTouchPos();
drawLine(ctx,touchX,touchY,12);
// Prevents an additional mousedown event being triggered
event.preventDefault();
}
function sketchpad_touchEnd() {
// Reset lastX and lastY to -1 to indicate that they are now invalid, since we have lifted the "pen"
lastX=-1;
lastY=-1;
}
// Draw something and prevent the default scrolling when touch movement is detected
function sketchpad_touchMove(e) {
// Update the touch co-ordinates
getTouchPos(e);
// During a touchmove event, unlike a mousemove event, we don't need to check if the touch is engaged, since there will always be contact with the screen by definition.
drawLine(ctx,touchX,touchY,12);
// Prevent a scrolling action as a result of this touchmove triggering.
event.preventDefault();
}
// Get the touch position relative to the top-left of the canvas
// When we get the raw values of pageX and pageY below, they take into account the scrolling on the page
// but not the position relative to our target div. We'll adjust them using "target.offsetLeft" and
// "target.offsetTop" to get the correct values in relation to the top left of the canvas.
function getTouchPos(e) {
if (!e)
var e = event;
if(e.touches) {
if (e.touches.length == 1) { // Only deal with one finger
var touch = e.touches[0]; // Get the information for finger #1
touchX=touch.pageX-touch.target.offsetLeft;
touchY=touch.pageY-touch.target.offsetTop;
}
}
}
// Set-up the canvas and add our event handlers after the page has loaded
function init() {
// Get the specific canvas element from the HTML document
canvas = document.getElementById('sketchpad');
// If the browser supports the canvas tag, get the 2d drawing context for this canvas
if (canvas.getContext)
ctx = canvas.getContext('2d');
// Check that we have a valid context to draw on/with before adding event handlers
if (ctx) {
// React to mouse events on the canvas, and mouseup on the entire document
canvas.addEventListener('mousedown', sketchpad_mouseDown, false);
canvas.addEventListener('mousemove', sketchpad_mouseMove, false);
window.addEventListener('mouseup', sketchpad_mouseUp, false);
// React to touch events on the canvas
canvas.addEventListener('touchstart', sketchpad_touchStart, false);
canvas.addEventListener('touchend', sketchpad_touchEnd, false);
canvas.addEventListener('touchmove', sketchpad_touchMove, false);
}
}
</script>
<style>
/* Some CSS styling */
#sketchpadapp {
/* Prevent nearby text being highlighted when accidentally dragging mouse outside confines of the canvas */
-webkit-touch-callout: none;
-webkit-user-select: none;
-khtml-user-select: none;
-moz-user-select: none;
-ms-user-select: none;
user-select: none;
}
.leftside {
float:left;
width:220px;
height:285px;
background-color:#def;
padding:10px;
border-radius:4px;
}
.rightside {
float:left;
margin-left:10px;
}
#sketchpad {
float:left;
height:300px;
width:400px;
border:2px solid #888;
border-radius:4px;
position:relative; /* Necessary for correct mouse co-ords in Firefox */
}
#clearbutton {
font-size: 15px;
padding: 10px;
-webkit-appearance: none;
background: #eee;
border: 1px solid #888;
}
</style>
</head>
<body onload="init()">
<div id="sketchpadapp">
<div class="leftside">
Touchscreen and mouse support HTML5 canvas sketchpad.<br/><br/>
Draw something by tapping or dragging.<br/><br/>
Works on iOS, Android and desktop/laptop touchscreens using Chrome/Firefox/Safari.<br/><br/>
<input type="submit" value="Clear Sketchpad" id="clearbutton" onclick="clearCanvas(canvas,ctx);">
</div>
<div class="rightside">
<canvas id="sketchpad" height="300" width="400">
</canvas>
</div>
</div>
</body>
</html>
But I can't manage to make it work on my mobile, as it only draws the first dot when touching!
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
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