see the news scroller on the top of this site
http://track.dc.gov/Agency/DH0
Any idea what library/functions this site uses to implment such a smooth scroller?
They have a very nicely formatted block of code you can study. Open your favorite JS debugger when you visit the site, wait for everything to get moving, and then press "Break All" or the equivalent in your debugger. You'll see something like the following:
Dashboard.UI.EndlessLine = function() {
var me = this;
me.jq = $(me);
me.classNames = { CONTAINER: "uiEndless", VIEW: "uiEndlessView", CANVAS: "uiEndlessCanvas", TILE: "uiEndlessTile" };
var canvas = null;
var view = null;
var tiles = null;
var x = 0;
var xx = 0;
var canvasWidth = 0;
var step = 1;
var delay = 40;
me.initialize = function(container, data, handler) {
required(container, "container");
required(data, "data");
required(handler, "handler");
container.addClass(me.classNames.CONTAINER);
view = newDiv(me.classNames.VIEW);
canvas = newDiv(me.classNames.CANVAS);
view.append(canvas);
container.append(view);
x = 0;
xx = 0;
canvasWidth = 0;
tiles = me.populateTiles(data, handler);
container.click(function() {
if (me.started()) me.stop(); else me.start();
});
};
me._resize = function(size) {
};
var moveId = 0;
me.start = function() {
me.stop();
me.tick();
}
me.stop = function() {
if (moveId > 0) clearTimeout(moveId);
moveId = 0;
}
me.started = function() {
return moveId > 0;
};
me.tick = function() {
var tile = tiles.current();
var width = tile.calculatedWidth;
if (x < width - step) {
x += step;
} else {
x = 0;
tile.css("left", canvasWidth + "px");
if (tiles.advance()) {
xx = 0;
canvasWidth = 0;
do {
current = tiles.current();
width = current.calculatedWidth;
current[0].style.left = canvasWidth + "px";
canvasWidth += width;
} while (!tiles.advance());
} else {
canvasWidth += width;
}
}
canvas[0].style.left = -(xx) + "px";
xx += step;
moveId = setTimeout(me.tick, delay);
}
me.populateTiles = function(data, handler) {
var tiles = new Dashboard.Core.List();
var viewWidth = view.contentWidth();
var maxHeight = 0;
each(data, function() {
var tile = newDiv(me.classNames.TILE);
handler.call(this, tile);
tile.css({ left: canvasWidth + "px", top: 0 });
canvas.append(tile);
var width = tile.outerWidth();
var height = tile.outerHeight();
if (maxHeight < height) maxHeight = height;
tile.calculatedWidth = width;
canvasWidth += width; // getting width may only be done after the element is attached to DOM
tiles.append(tile);
view.height(height);
});
return tiles.createCycle();
}
}
I'm impressed -- everything looks professional and nicely namespaced.
Update: If you want an explanation of how it works, focus on the tick method defined above. Glossing over all the details (cause I haven't really studied it myself), it calculates a step size, moves the message element to the left by the some amount, and schedules the next tick call for 40 milliseconds in the future.
jQuery enthusiast, Remy Sharp, has his own Marquee Plugin that you can implement pretty easily. You can gather deeper details of it on his blog or by visiting the demo page.
For Mootools users, there's Mooquee.
You can also view the actual code for this example online at http://track.dc.gov/Resource/Script/ - do a search for "uiEndless" to find the target-scripting.
Related
I have a function that adds random images to my divs that disappear over time and create a mouse trail. My issue is: there are double images.
I'd like to add something that checks if the background url is already located on the page and if that's the case, skips to the next in the array and check it again until until it comes across one that is not there. So like a loop that refreshes every time a 'trail' is being created.
Maybe I am asking for something that won't work? What if all the images are already on the page? I don't really have an answer for it and I also don't have an idea how to solve that problem yet.
For now I tried adding a counter that checks the usedImages and counts them, but it seems to have flaws and I am unsure where to look or how to fix it. Does anyone have any tips on how to do this? Is it even possible?
My fiddle
var bgImages = new Array(
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2019/05/schraegluftbild-1024x725.jpg",
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2019/05/pikto-608x1024.jpg",
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2019/05/Jettenhausen-EG-Grundriss-913x1024.jpg",
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2019/05/lageplan-945x1024.jpg",
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2019/05/Jettenhausen-EG-Grundriss-913x1024.jpg",
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2019/05/Jettenhauser-Esch-Modell-2-1024x768.jpg",
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2019/07/DSCN3481-1024x768.jpg",
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2019/07/zoom-in-3_ASTOC-1024x683.jpg",
"https://www.studiourbanestrategien.com/wordpress/wp-content/uploads/2016/07/IMG_1345-1024x768.jpg"
);
const numberOfImages = 10;
const timesPerSecond = .1;
var usedImages = {};
var usedImagesCount = 0;
function preloadImages(images) {
for (i = 0; i < images.length; i++) {
let l = document.createElement('link')
l.rel = 'preload'
l.as = 'image'
l.href = images[i]
document.head.appendChild(l);
}
}
function animate(e) {
var image = document.createElement('div');
image.classList.add('trail');
var sizew = 200;
var sizeh = 200;
image.style.transition = '3s ease';
image.style.position = 'fixed';
image.style.top = e.pageY - sizeh / 2 + 'px';
image.style.left = e.pageX - sizew / 2 + 'px';
image.style.width = sizew + 'px';
image.style.height = sizeh + 'px';
var random = Math.floor(Math.random() * (bgImages.length));
if (!usedImages[random]) {
image.style.backgroundImage = "url(" + bgImages[random] + ")";
usedImages[random] = true;
usedImagesCount++;
if (usedImagesCount === bgImages.length) {
usedImagesCount = 0;
usedImages = {};
}
} else {
animate(e);
}
console.log(usedImages);
console.log(usedImagesCount);
image.style.backgroundSize = 'cover';
image.style.pointerEvents = 'none';
image.style.zIndex = 1;
document.body.appendChild(image);
//opacity and blur animations
window.setTimeout(function() {
image.style.opacity = 0;
image.style.filter = 'blur(20px)';
}, 40);
window.setTimeout(function() {
document.body.removeChild(image);
}, 2100);
};
window.onload = function() {
preloadImages(bgImages);
var wait = false;
window.addEventListener('mousemove', function(e) {
if (!wait) {
wait = true;
setTimeout(() => {
wait = false
}, timesPerSecond * 800);
animate(e);
}
});
};
I am using a javascript for falling images. (1) I want the images to cover the whole page, but they are only displaying in the header area. I don't know what portion to change to make it cover the whole page. It's a wordpress site, so maybe that has something to do with it? I put the call to the script in the head section. This is the script:
var image="http://abyssinianguineapigtips.com/wp-content/uploads/2014/11/onepoop.png"; //Image path should be given here
var no = 15; // No of images should fall
var time = 0; // Configure whether image should disappear after x seconds (0=never):
var speed = 10; // Fix how fast the image should fall
var i, dwidth = 900, dheight =500;
var nht = dheight;
var toppos = 0;
if(document.all){
var ie4up = 1;
}else{
var ie4up = 0;
}
if(document.getElementById && !document.all){
var ns6up = 1;
}else{
var ns6up = 0;
}
function getScrollXY() {
var scrOfX = 10, scrOfY = 10;
if( typeof( window.pageYOffset ) == 'number' ) {
//Netscape compliant
scrOfY =window.pageYOffset;
scrOfX = window.pageXOffset;
} else if( document.body && ( document.body.scrollLeft || document.body.scrollTop ) ) {
//DOM compliant
scrOfY = document.body.scrollTop;
scrOfX = document.body.scrollLeft;
} else if( document.documentElement &&
( document.documentElement.scrollLeft || document.documentElement.scrollTop ) ) {
//IE6 standards compliant mode
scrOfY = document.documentElement.scrollTop;
scrOfX = document.documentElement.scrollLeft;
}
return [ scrOfX, scrOfY ];
}
var timer;
function ranrot()
{
var a = getScrollXY()
if(timer)
{
clearTimeout(timer);
}
toppos = a[1];
dheight = nht+a[1];
//alert(dheight);
timer = setTimeout('ranrot()',2000);
}
ranrot();
function iecompattest()
{
if(document.compatMode && document.compatMode!="BackCompat")
{
return document.documentElement;
}else{
return document.body;
}
}
if (ns6up) {
dwidth = window.innerWidth;
dheight = window.innerHeight;
}
else if (ie4up) {
dwidth = iecompattest().clientWidth;
dheight = iecompattest().clientHeight;
}
nht = dheight;
var cv = new Array();
var px = new Array(); //position variables
var py = new Array(); //position variables
var am = new Array(); //amplitude variables
var sx = new Array(); //step variables
var sy = new Array(); //step variables
for (i = 0; i < no; ++ i) {
cv[i] = 0;
px[i] = Math.random()*(dwidth-100); // set position variables
py[i] = Math.random()*dheight; // set position variables
am[i] = Math.random()*20; // set amplitude variables
sx[i] = 0.02 + Math.random()/10; // set step variables
sy[i] = 0.7 + Math.random(); // set step variables
document.write("<div id=\"dot"+ i +"\" style=\"POSITION: absolute; Z-INDEX: "+ i +"; VISIBILITY: visible; TOP: 15px;LEFT: 15px;\"><img src='"+image+"' border=\"0\"><\/div>");
}
function animation() { // animation function
for (i = 0; i < no; ++ i) { // iterate for every dot
py[i] += sy[i];
if (py[i] > dheight-50) {
px[i] = Math.random()*(dwidth-am[i]-100);
py[i] = toppos;
sx[i] = 0.02 + Math.random()/10;
sy[i] = 0.7 + Math.random();
}
cv[i] += sx[i];
document.getElementById("dot"+i).style.top=py[i]+"px";
document.getElementById("dot"+i).style.left=px[i] + am[i]*Math.sin(cv[i])+"px";
}
atime=setTimeout("animation()", speed);
}
function hideimage(){
if (window.atime) clearTimeout(atime)
for (i=0; i<no; i++)
document.getElementById("dot"+i).style.visibility="hidden"
}
if (ie4up||ns6up){
animation();
if (time>0)
setTimeout("hideimage()", time*1000)
}
animation();
/* Free Script provided by HIOXINDIA */
/* visit us at http://www.hscripts.com */
/* This is a copyright product of hioxindia.com */
The page is here.
My second question is the best way to stop the script from executing when someone clicks on the stop sign image. I've read 10 different answers to similar questions here on stackoverflow. So my thought is to make it happen by using:
<img src="stop.png" onclick="myEventHandler(event);" />
and I add:
function myEventHandler(e)
{
if (!e)
e = window.event;
//IE9 & Other Browsers
if (e.stopPropagation) {
e.stopPropagation();
}
//IE8 and Lower
else {
e.cancelBubble = true;
}
}'
to the js file. (I got that from here)
Is that the best way to make it stop with an onclick?
This was a Z-index problem/ Changing
document.write("<div id=\"dot"+ i +"\" style=\"POSITION: absolute; Z-INDEX: "+ i +"; VISIBILITY: visible; TOP: 15px;LEFT: 15px;\"><img src='"+image+"' border=\"0\"><\/div>");
}
to
document.write("<div class=\"img-object\" id=\"dot"+ i +"\" style=\"POSITION: absolute; Z-INDEX: "+ (i + 1000) +"; VISIBILITY: visible; TOP: 15px;LEFT: 15px;\"><img src='"+image+"' border=\"0\"><\/div>");
}
made it cover the whole page.
And to stop the animation when clicking on an image, this function works:
(html):
<img src="stopsign.png" onclick="stopAnimation();" />
and the function:
function stopAnimation() {
if (window.atime) {clearTimeout(atime);}
jQuery('.img-object').hide();
}
We're working with the HTML5 canvas, displaying lots of images at one time.
This is working pretty well but recently we've had a problem with chrome.
When drawing images on to a canvas you seem to reach a certain point where the performance degrades very quickly.
It's not a slow effect, it seems that you go right from 60fps to 2-4fps.
Here's some reproduction code:
// Helpers
// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Math/random
function getRandomInt(min, max) { return Math.floor(Math.random() * (max - min + 1)) + min; }
// http://www.paulirish.com/2011/requestanimationframe-for-smart-animating/
window.requestAnimFrame = (function () { return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || function (callback) { window.setTimeout(callback, 1000 / 60); }; })();
// https://github.com/mrdoob/stats.js
var Stats = function () { var e = Date.now(), t = e; var n = 0, r = Infinity, i = 0; var s = 0, o = Infinity, u = 0; var a = 0, f = 0; var l = document.createElement("div"); l.id = "stats"; l.addEventListener("mousedown", function (e) { e.preventDefault(); y(++f % 2) }, false); l.style.cssText = "width:80px;opacity:0.9;cursor:pointer"; var c = document.createElement("div"); c.id = "fps"; c.style.cssText = "padding:0 0 3px 3px;text-align:left;background-color:#002"; l.appendChild(c); var h = document.createElement("div"); h.id = "fpsText"; h.style.cssText = "color:#0ff;font-family:Helvetica,Arial,sans-serif;font-size:9px;font-weight:bold;line-height:15px"; h.innerHTML = "FPS"; c.appendChild(h); var p = document.createElement("div"); p.id = "fpsGraph"; p.style.cssText = "position:relative;width:74px;height:30px;background-color:#0ff"; c.appendChild(p); while (p.children.length < 74) { var d = document.createElement("span"); d.style.cssText = "width:1px;height:30px;float:left;background-color:#113"; p.appendChild(d) } var v = document.createElement("div"); v.id = "ms"; v.style.cssText = "padding:0 0 3px 3px;text-align:left;background-color:#020;display:none"; l.appendChild(v); var m = document.createElement("div"); m.id = "msText"; m.style.cssText = "color:#0f0;font-family:Helvetica,Arial,sans-serif;font-size:9px;font-weight:bold;line-height:15px"; m.innerHTML = "MS"; v.appendChild(m); var g = document.createElement("div"); g.id = "msGraph"; g.style.cssText = "position:relative;width:74px;height:30px;background-color:#0f0"; v.appendChild(g); while (g.children.length < 74) { var d = document.createElement("span"); d.style.cssText = "width:1px;height:30px;float:left;background-color:#131"; g.appendChild(d) } var y = function (e) { f = e; switch (f) { case 0: c.style.display = "block"; v.style.display = "none"; break; case 1: c.style.display = "none"; v.style.display = "block"; break } }; var b = function (e, t) { var n = e.appendChild(e.firstChild); n.style.height = t + "px" }; return { REVISION: 11, domElement: l, setMode: y, begin: function () { e = Date.now() }, end: function () { var f = Date.now(); n = f - e; r = Math.min(r, n); i = Math.max(i, n); m.textContent = n + " MS (" + r + "-" + i + ")"; b(g, Math.min(30, 30 - n / 200 * 30)); a++; if (f > t + 1e3) { s = Math.round(a * 1e3 / (f - t)); o = Math.min(o, s); u = Math.max(u, s); h.textContent = s + " FPS (" + o + "-" + u + ")"; b(p, Math.min(30, 30 - s / 100 * 30)); t = f; a = 0 } return f }, update: function () { e = this.end() } } }
// Firefox events suck
function getOffsetXY(eventArgs) { return { X: eventArgs.offsetX == undefined ? eventArgs.layerX : eventArgs.offsetX, Y: eventArgs.offsetY == undefined ? eventArgs.layerY : eventArgs.offsetY }; }
function getWheelDelta(eventArgs) { if (!eventArgs) eventArgs = event; var w = eventArgs.wheelDelta; var d = eventArgs.detail; if (d) { if (w) { return w / d / 40 * d > 0 ? 1 : -1; } else { return -d / 3; } } else { return w / 120; } }
// Reproduction Code
var stats = new Stats();
document.body.appendChild(stats.domElement);
var masterCanvas = document.getElementById('canvas');
var masterContext = masterCanvas.getContext('2d');
var viewOffsetX = 0;
var viewOffsetY = 0;
var viewScaleFactor = 1;
var viewMinScaleFactor = 0.1;
var viewMaxScaleFactor = 10;
var mouseWheelSensitivity = 10; //Fudge Factor
var isMouseDown = false;
var lastMouseCoords = null;
var imageDimensionPixelCount = 25;
var paddingPixelCount = 2;
var canvasDimensionImageCount = 50;
var totalImageCount = Math.pow(canvasDimensionImageCount, 2);
var images = null;
function init() {
images = createLocalImages(totalImageCount, imageDimensionPixelCount);
initInteraction();
renderLoop();
}
function initInteraction() {
var handleMouseDown = function (eventArgs) {
isMouseDown = true;
var offsetXY = getOffsetXY(eventArgs);
lastMouseCoords = [
offsetXY.X,
offsetXY.Y
];
};
var handleMouseUp = function (eventArgs) {
isMouseDown = false;
lastMouseCoords = null;
}
var handleMouseMove = function (eventArgs) {
if (isMouseDown) {
var offsetXY = getOffsetXY(eventArgs);
var panX = offsetXY.X - lastMouseCoords[0];
var panY = offsetXY.Y - lastMouseCoords[1];
pan(panX, panY);
lastMouseCoords = [
offsetXY.X,
offsetXY.Y
];
}
};
var handleMouseWheel = function (eventArgs) {
var mouseX = eventArgs.pageX - masterCanvas.offsetLeft;
var mouseY = eventArgs.pageY - masterCanvas.offsetTop;
var zoom = 1 + (getWheelDelta(eventArgs) / mouseWheelSensitivity);
zoomAboutPoint(mouseX, mouseY, zoom);
if (eventArgs.preventDefault !== undefined) {
eventArgs.preventDefault();
} else {
return false;
}
}
masterCanvas.addEventListener("mousedown", handleMouseDown, false);
masterCanvas.addEventListener("mouseup", handleMouseUp, false);
masterCanvas.addEventListener("mousemove", handleMouseMove, false);
masterCanvas.addEventListener("mousewheel", handleMouseWheel, false);
masterCanvas.addEventListener("DOMMouseScroll", handleMouseWheel, false);
}
function pan(panX, panY) {
masterContext.translate(panX / viewScaleFactor, panY / viewScaleFactor);
viewOffsetX -= panX / viewScaleFactor;
viewOffsetY -= panY / viewScaleFactor;
}
function zoomAboutPoint(zoomX, zoomY, zoomFactor) {
var newCanvasScale = viewScaleFactor * zoomFactor;
if (newCanvasScale < viewMinScaleFactor) {
zoomFactor = viewMinScaleFactor / viewScaleFactor;
} else if (newCanvasScale > viewMaxScaleFactor) {
zoomFactor = viewMaxScaleFactor / viewScaleFactor;
}
masterContext.translate(viewOffsetX, viewOffsetY);
masterContext.scale(zoomFactor, zoomFactor);
viewOffsetX = ((zoomX / viewScaleFactor) + viewOffsetX) - (zoomX / (viewScaleFactor * zoomFactor));
viewOffsetY = ((zoomY / viewScaleFactor) + viewOffsetY) - (zoomY / (viewScaleFactor * zoomFactor));
viewScaleFactor *= zoomFactor;
masterContext.translate(-viewOffsetX, -viewOffsetY);
}
function renderLoop() {
clearCanvas();
renderCanvas();
stats.update();
requestAnimFrame(renderLoop);
}
function clearCanvas() {
masterContext.clearRect(viewOffsetX, viewOffsetY, masterCanvas.width / viewScaleFactor, masterCanvas.height / viewScaleFactor);
}
function renderCanvas() {
for (var imageY = 0; imageY < canvasDimensionImageCount; imageY++) {
for (var imageX = 0; imageX < canvasDimensionImageCount; imageX++) {
var x = imageX * (imageDimensionPixelCount + paddingPixelCount);
var y = imageY * (imageDimensionPixelCount + paddingPixelCount);
var imageIndex = (imageY * canvasDimensionImageCount) + imageX;
var image = images[imageIndex];
masterContext.drawImage(image, x, y, imageDimensionPixelCount, imageDimensionPixelCount);
}
}
}
function createLocalImages(imageCount, imageDimension) {
var tempCanvas = document.createElement('canvas');
tempCanvas.width = imageDimension;
tempCanvas.height = imageDimension;
var tempContext = tempCanvas.getContext('2d');
var images = new Array();
for (var imageIndex = 0; imageIndex < imageCount; imageIndex++) {
tempContext.clearRect(0, 0, imageDimension, imageDimension);
tempContext.fillStyle = "rgb(" + getRandomInt(0, 255) + ", " + getRandomInt(0, 255) + ", " + getRandomInt(0, 255) + ")";
tempContext.fillRect(0, 0, imageDimension, imageDimension);
var image = new Image();
image.src = tempCanvas.toDataURL('image/png');
images.push(image);
}
return images;
}
// Get this party started
init();
And a jsfiddle link for your interactive pleasure:
http://jsfiddle.net/BtyL6/14/
This is drawing 50px x 50px images in a 50 x 50 (2500) grid on the canvas. I've also quickly tried with 25px x 25px and 50 x 50 (2500) images.
We have other local examples that deal with bigger images and larger numbers of images and the other browser start to struggle with these at higher values.
As a quick test I jacked up the code in the js fiddle to 100px x 100px and 100 x 100 (10000) images and that was still running at 16fps when fully zoomed out. (Note: I had to lower the viewMinScaleFactor to 0.01 to fit it all in when zoomed out.)
Chrome on the other hand seems to hit some kind of limit and the FPS drops from 60 to 2-4.
Here's some info about what we've tried and the results:
We've tried using setinterval rather than requestAnimationFrame.
If you load 10 images and draw them 250 times each rather than 2500 images drawn once each then the problem goes away. This seems to indicate that chrome is hitting some kind of limit/trigger as to how much data it's storing about the rendering.
We have culling (not rendering images outside of the visual range) in our more complex examples and while this helps it's not a solution as we need to be able to show all the images at once.
We have the images only being rendered if there have been changes in our local code, against this helps (when nothing changes, obviously) but it isn't a full solution because the canvas should be interactive.
In the example code we're creating the images using a canvas, but the code can also be run hitting a web service to provide the images and the same behaviour (slowness) will be seen.
We've found it very hard to even search for this issue, most results are from a couple of years ago and woefully out of date.
If any more information would be useful then please ask!
EDIT: Changed js fiddle URL to reflect the same code as in the question. The code itself didn't actually change, just the formatting. But I want to be consistent.
EDIT: Updated jsfiddle and and code with css to prevent selection and call requestAnim after the render loop is done.
In Canary this code freezes it on my computer. As to why this happens in Chrome the simple answer is that it uses a different implementation than f.ex. FF. In-depth detail I don't know, but there is obviously room for optimizing the implementation in this area.
I can give some tip however on how you can optimize the given code to make it run in Chrome as well :-)
There are several things here:
You are storing each block of colors as images. This seem to have a huge performance impact on Canary / Chrome.
You are calling requestAnimationFrame at the beginning of the loop
You are clearing and rendering even if there are no changes
Try to (addressing the points):
If you only need solid blocks of colors, draw them directly using fillRect() instead and keep the color indexes in an array (instead of images). Even if you draw them to an off-screen canvas you will only have to do one draw to main canvas instead of multiple image draw operations.
Move requestAnimationFrame to the end of the code block to avoid stacking.
Use dirty flag to prevent unnecessary rendering:
I modified the code a bit - I modified it to use solid colors to demonstrate where the performance impact is in Chrome / Canary.
I set a dirty flag in global scope as true (to render the initial scene) which is set to true each time the mouse move occur:
//global
var isDirty = true;
//mouse move handler
var handleMouseMove = function (eventArgs) {
// other code
isDirty = true;
// other code
};
//render loop
function renderLoop() {
if (isDirty) {
clearCanvas();
renderCanvas();
}
stats.update();
requestAnimFrame(renderLoop);
}
//in renderCanvas at the end:
function renderCanvas() {
// other code
isDirty = false;
}
You will of course need to check for caveats for the isDirty flag elsewhere and also introduce more criteria if it's cleared at the wrong moment. I would store the old position of the mouse and only (in the mouse move) if it changed set the dirty flag - I didn't modify this part though.
As you can see you will be able to run this in Chrome and in FF at a higher FPS.
I also assume (I didn't test) that you can optimize the clearCanvas() function by only drawing the padding/gaps instead of clearing the whole canvas. But that need to be tested.
Added a CSS-rule to prevent the canvas to be selected when using the mouse:
For further optimizing in cases such as this, which is event driven, you don't actually need an animation loop at all. You can just call the redraw when the coords or mouse-wheel changes.
Modification:
http://jsfiddle.net/BtyL6/10/
This was a legitimate bug in chrome.
https://code.google.com/p/chromium/issues/detail?id=247912
It has now been fixed and should be in a chrome mainline release soon.
I'm trying to create something like a very simple particle system. No physics required at this point, just divs that are animated to look like bubbles, or bees, or whatever. The code below creates the divs and through CSS I can make them change position, floating upwards. But I can't seem to workout how to destroy particles. Each particle does it's motion and then returns back to it's original point. I would prefer if it was removed completely.
Thank you.
/* ==================== PARTICLES CONTROLLER ==================== */
/**
* Particle controller interates through all elements with
* CSS class name PARTICLE_CSS and when found a ParticleController is instantiated
* for each of the elements.
*/
function ParticleBaseController(){
var ParticleContainer = document.querySelectorAll(PARTICLE_CSS),
ParticleContainerLength = ParticleContainer.length;
for (var i = ParticleContainerLength - 1; i >= 0; i--){
new ParticleController(ParticleContainer[i]);
};
};
function ParticleController(element) {
var particleElement, fragment = document.createDocumentFragment();
var numberOfParticles = 1;
for (var i = 0; i < numberOfParticles; i ++) {
particleElement = document.createElement("div");
particleElement.addClassName(PARTICLE_ELEMENT_CSS_CLASS);
var Ypos = Math.floor((Math.random()*200)+1);
var Xpos = Math.floor((Math.random()*200)+1);
particleElement.style.top = Ypos + "px";
particleElement.style.left = Xpos + "px";
fragment.appendChild(particleElement);
}
element.appendChild(fragment);
setTimeout(ParticleBaseController, 3000);
};
This worked for me. I am guessing that the way it works is that particles are only appended to the container as long as there are fewer than 15. Although I do not know how they are actually destroyed. But on screen I can only ever see 15 particles at a time, or however many I set then number to.
/* ==================== PARTICLES CONTROLLER ==================== */
const NumberOfParticles = 15;
function smoking()
{
var container = document.getElementById('particleContainer');
for (var i = 0; i < NumberOfParticles; i++)
{
container.appendChild(createParticle());
}
}
function randomFloat(low, high)
{
return low + Math.random() * (high - low);
}
function createParticle()
{
var particleDiv = document.createElement('div');
particleDiv.style.top = "-300px";
particleDiv.style.left = "200px"
particleDiv.style.webkitAnimationName = 'smoke-rise, smoke-fade';
var SmokeDuration = randomFloat(5, 10)+"s";
var FadeDuration = randomFloat(4, 11)+"s";
var SmokeDelay = randomFloat(0, 5)+"s";
var FadeDelay = randomFloat(2, 9)+"s";
particleDiv.style.webkitAnimationDuration = SmokeDuration + ', ' + FadeDuration;
particleDiv.style.webkitAnimationDelay = SmokeDelay + ', ' + FadeDelay;
return particleDiv;
}
window.addEventListener("DOMContentLoaded", smoking, false);
I'm using Raphael.js. Everytime i load the page i get an error that reads:
con is undefined
x = con.x
I looked up con in the Raphael documentation, and this is what i found:
var con = R._getContainer.apply(0, arguments),
container = con && con.container,
x = con.x,
y = con.y,
width = con.width,
height = con.height;
//...
con is clearly defined here. Here is the code I am trying to load:
var paper = new Raphael(ele('canvas_container'), 500, 500);
window.onload = function() {
var circle = paper.circle(100,100,100);
for (i = 0; i < 5; i++) {
var multiplier = i * 5;
paper.circle(250 + (2 * multiplier), 100 + multiplier, 50 - multiplier);
}
}
Has anyone else gotten this error? Is this a bug in the version of Raphael that I have or is there some other problem?
Try moving the paper instantiation inside your window's load function:
window.onload = function() {
var paper = new Raphael(ele('canvas_container'), 500, 500);
var circle = paper.circle(100,100,100);
for (i = 0; i < 5; i++) {
var multiplier = i * 5;
paper.circle(250 + (2 * multiplier), 100 + multiplier, 50 - multiplier);
}
}
If you try to get an element by its id before the DOM is ready, getElementById won't return anything. As you can see here, trying your code on an empty document shows the same result.
Raphael.js expects there to be a hard coded HTML element on the page with the name of the Raphael canvas (ie: "canvas_container"). If the HTML element is created during run time (dynamically in your JavaScript code), it will throw this error.
R._engine.create = function () {
var con = R._getContainer.apply(0, arguments),
container = con && con.container,
x = con.x,
y = con.y,
width = con.width,
height = con.height;
if (!container) {
throw new Error("SVG container not found.");
}
var cnvs = $("svg"),
css = "overflow:hidden;",
isFloating;
x = x || 0;
y = y || 0;
width = width || 512;
height = height || 342;
$(cnvs, {
height: height,
version: 1.1,
width: width,
xmlns: "http://www.w3.org/2000/svg"
});
if (container == 1) {
cnvs.style.cssText = css + "position:absolute;left:" + x + "px;top:" + y + "px";
R._g.doc.body.appendChild(cnvs);
isFloating = 1;
} else {
cnvs.style.cssText = css + "position:relative";
if (container.firstChild) {
container.insertBefore(cnvs, container.firstChild);
} else {
container.appendChild(cnvs);
}
}
container = new R._Paper;
container.width = width;
container.height = height;
container.canvas = cnvs;
container.clear();
container._left = container._top = 0;
isFloating && (container.renderfix = function () {});
container.renderfix();
return container;
};