I have an absolutely positioned canvas laid over a webpage. The canvas has some items created using Paper.js. I want the canvas (or the view) to move in sync with the scrolling of the webpage.
The canvas covers the entire screen (1920 x 1080) not the webpage (1920 x variable length). So, just shifting the canvas's fixed position does not work. It is no longer overlaid on the entire screen.
Later, I found about views in Paper.js and I can use the following line to scroll the view:
project.view.scrollBy(new Point(0, 450));
The problem is that I cannot figure out the value I need to put in place for 450 so that the scrolling is always synchronized.
I do use the following JavaScript to animate the scrolling action on the webpage whenver up and down keys are pressed:
$("section.scrollable").animate({scrollTop : $("section.scrollable").scrollTop() + 300 })
However, putting 300 in the scrollBy values doesn't move the canvas and the webpage in proper synchronization either.
This pen is a very minimal example to show my problem. You might prefer to see it in debug mode.
You can drag over the canvas to create orange lines.
There are three heading and three corresponding lines drawn on an overlaid canvas. The canvas is 1920px wide and 1080px high.
The third heading falls below 1080px so its line is not visible on the canvas. However, it becomes visible when I scroll inside the Paper view by using the following line:
project.view.scrollBy(new Point(0, 600));
Here is my problem with following constraints:
The canvas position has to stay fixed. So, it won't scroll with the rest of the document.
However, the view for Paper.js has to shift in sync with the document so that the lines, paths and other items don't change their relative positions with respect to the webpage. For example, the lines still stay under the same headings.
You need to listen to scroll event and every time it happens, update your paper.js scene y position.
Rather than using the view, I found that using the active layer was more convenient but you could theoretically do the same with the view.
Here's a simple fiddle that should get you on the track.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Debug Paper.js</title>
<script src="https://unpkg.com/acorn"></script>
<script src="https://unpkg.com/paper"></script>
<style>
html,
body {
margin : 0;
height : 100%;
}
canvas {
position : fixed;
top : 0;
left : 0;
width : 100vw;
height : 100vh;
}
section {
max-width : 500px;
margin : auto;
}
</style>
</head>
<body>
<section>
<div>
<h1>title 1</h1>
<p>...</p>
</div>
<div>
<h1>title 2</h1>
<p>...</p>
</div>
</section>
<canvas id="canvas" resize></canvas>
<script>
paper.setup('canvas');
new paper.Path.Circle({
center: paper.view.center,
radius: 50,
fillColor: 'orange'
});
const originalY = paper.view.center.y;
const update = () => {
const yOffset = document.scrollingElement.scrollTop;
paper.view.center.y = originalY - yOffset;
};
window.addEventListener('scroll', update);
</script>
</body>
</html>
I have a website that i'm working on locally, and it will be displayed through a projector for a presentation. Is there a way for me to scale it to the full size of the projection or if it were to be displayed on bigger screens without having to use all the media queries! I tried adding:
<meta name="viewport" content="initial-scale = 1.0,maximum-scale = 1.0" />
But i don't think it will do the trick! Any input from you is welcomed
Edit:
Just thought i'd add that the website is in a 1000*800 container on the original size, i just want it to grow a bit whenever a screen gets bigger
if using Bootstrap then wrapping all content in a container-fluid div will use the full screen width (and therefore projection width).
<div class="container-fluid">
...// content
</div>
I'd try getting the browser window resolution and setting the width and height accordingly if the resolution goes beyond a specific one.
<script>
function setContentSize(){
var ww = window.innderWidth;
var wh = window.innderHeight;
ID.style.width = 1000 +"px";
ID.style.width = 800 +"px"; //ID must be set in HTML
if(ww > what you want ){
ID.style.width = what you want +"px";
}
}
</script>
etc. You probably can work it out
And you can load it up with window.addEventListener("resize", setContentSize);
To auto-zoom the whole page, one solution is using transform: scale(). The page needs to sit inside a container for this to work. First set the origin in css for the container:
div#page-container {
transform-origin: 0 0;
}
Then change the scale factor with javascript (in my case jQuery):
$(function() {
var ratio = $('div#page-container').width() / $(document).width();
$('div#page-container').css('transform', 'scale(' + (1.0 / ratio) + ')');
});
Here is a Fiddle.
I'm working on a website that fits within a specific width and height (an 885x610 div with a 1px border and 3px top margin). I would like the user to never have to scroll or zoom in order to see the entire div; it should always be fully visible. Since devices have a wide variety of resolutions and aspect ratios, the idea that came to mind was to set the "viewport" meta tag dynamically with JavaScript. This way, the div will always be the same dimensions, different devices will have to be zoomed differently in order to fit the entire div in their viewport. I tried out my idea and got some strange results.
The following code works on the first page load (tested in Chrome 32.0.1700.99 on Android 4.4.0), but as I refresh, the zoom level changes around. Also, if I comment out the alert, it doesn't work even on the first page load.
Fiddle
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, height=device-height, initial-scale=1.0">
<script type="text/javascript">
function getViewportWidth() {
if (window.innerWidth) {
return window.innerWidth;
}
else if (document.body && document.body.offsetWidth) {
return document.body.offsetWidth;
}
else {
return 0;
}
}
function getViewportHeight() {
if (window.innerHeight) {
return window.innerHeight;
}
else if (document.body && document.body.offsetHeight) {
return document.body.offsetHeight;
}
else {
return 0;
}
}
if (/Android|webOS|iPhone|iPad|iPod|BlackBerry/i.test(navigator.userAgent)) {
var actual_width = getViewportWidth();
var actual_height = getViewportHeight();
var min_width = 887;
var min_height = 615;
var ratio = Math.min(actual_width / min_width, actual_height / min_height);
if (ratio < 1) {
document.querySelector('meta[name="viewport"]').setAttribute('content', 'initial-scale=' + ratio + ', maximum-scale=' + ratio + ', minimum-scale=' + ratio + ', user-scalable=yes, width=' + actual_width);
}
}
alert(document.querySelector('meta[name="viewport"]').getAttribute('content'));
</script>
<title>Test</title>
<style>
body {
margin: 0;
}
div {
margin: 3px auto 0;
width: 885px;
height: 610px;
border: 1px solid #f00;
background-color: #fdd;
}
</style>
</head>
<body>
<div>
This div is 885x610 (ratio is in between 4:3 and 16:10) with a 1px border and 3px top margin, making a total of 887x615.
</div>
</body>
</html>
What can I do to have this website scale to fit both the width and the height?
It's possible to get a consistent behavior. But it's unfortunately very complex. I am working on a script that detects spoofed agents and dynamically rescale the viewport to desktop or other spoofed agents accordingly. I was also facing the zooming issue with Android/Chrome as well as the iOS emulator...
To get around it, you need to disable zooming and/or set the viewport twice. On the first pass, preferably inline in the <head> as you do now, you set your scale and disable user-scaling temporarily to prevent the zoom issue, using the same fixed value for all 3 scales like:
document.querySelector('meta[name=viewport]').setAttribute('content', 'width='+width+',minimum-scale='+scale+',maximum-scale='+scale+',initial-scale='+scale);
Then to restore zooming you set the viewport again on DOMContentLoaded, with the same scale, except that this time you set normal min/max scale values to restore user-scaling:
document.querySelector('meta[name=viewport]').setAttribute('content', 'width='+width+',minimum-scale=0,maximum-scale=10');
In your context, because the layout is fixed and larger than the viewport, initial-scale='+scale is perhaps needed for a more sound alternative for DOMContentLoaded:
document.querySelector('meta[name=viewport]').setAttribute('content', 'width='+width+',minimum-scale=0,maximum-scale=10,initial-scale='+scale);
That should get the viewport to rescale as you would like in Webkit browsers without zooming problems. I say only in webkit because sadly IE and Firefox do not support changing the viewport as per this Browser Compatibility Table for Viewports, Dimensions and Device Pixel Ratios shows: http://www.quirksmode.org/mobile/tableViewport.html
IE has its own way to change the viewport dynamically which is actually needed for IE snap modes to be responsive.
http://timkadlec.com/2012/10/ie10-snap-mode-and-responsive-design/
So for IEMobile and IE SnapMode (IE10&11) you need to dynamically insert an inline <style> in the <head> with something like.
<script>
var s = document.createElement('style');
s.appendChild(document.createTextNode('#-ms-viewport{width:'+width+'px')+';}'));
document.head.appendChild(s);
</script>
And unfortunately, Firefox has neither: The viewport is set for once and for all as the above compatibility table shows. At the moment, for lack of other methods, using CSS Transform (as #imcg pointed out) is the only way to alter the viewport in FireFox Mobile on Android or Gecko OS. I have just tested it and it works in the context of a fixed size design. (In "Responsive Design context", the layout can be rescaled larger via CSS Transform, say at desktop size on a phone, but Firefox still read the phone size MQs. So that's something to be mindful off in RWD context. /aside from webkit)
Though, I have noticed some random Webkit crashes with CSSTransform on Android so I would recommend the viewport method for Safari/Chrome/Opera as more reliable one.
In addition, in order to get cross-browser reliability for the viewport width, you also have to face/fix the overall inconsistency between browsers for innerWidth (note that documentElement.clientWidth is much more reliable to get the accurate layout pixel width over innerWidth) and you also have to deal with devicePixelRatio discrepancies as indicated on the quirksmode.org table.
Update: Actually after some more thought into a solution for my own problem with Firefox, I just found out a way to override the viewport in Firefox Mobile, using document.write(), applied just once:
document.write('<meta name="viewport" content="width='+width+'px,initial-scale='+scale+'">');
Just tested this successfully in both Webkit and Firefox with no zooming issues. I can't test on Window Phones, so I am not sure itf document.write works for IEMobile...
I know this is two years late, but I spent a lot of time working on this problem, and would like to share my solution. I found the original question to be very helpful, so I feel that posting this answer is my way of giving back. My solution works on an iPhone6 and a 7" Galaxy Tab. I don't know how it fares on other devices, but I'm guessing it should mostly behave.
I separated the viewport logic into an external file so that it is easy to
reuse. First, here's how you would use the code:
<HTML>
<HEAD>
<SCRIPT type="text/javascript" src="AutoViewport.js"></SCRIPT>
</HEAD>
<BODY>
<SCRIPT>
AutoViewport.setDimensions(yourNeededWidth, yourNeededHeight);
</SCRIPT>
<!-- The rest of your HTML goes here -->
</BODY>
</HTML>
In actuality, I padded my desired width and height by a slight amount (15 pixels or so) so that my intended display was framed nicely. Also please note from the usage code that you do not have to specify a viewport tag in your HTML. My library will automatically create one for you if one does not already exist.
Here is AutoViewport.js:
/** Steven Yang, July 2016
Based on http://stackoverflow.com/questions/21419404/setting-the-viewport-to-scale-to-fit-both-width-and-height , this Javascript code allows you to
cause the viewport to auto-adjust based on a desired pixel width and height
that must be visible on the screen.
This code has been tested on an iPhone6 and a 7" Samsung Galaxy Tab.
In my case, I have a game with the exact dimensions of 990 x 660. This
script allows me to make the game render within the screen, regardless
of whether you are in landscape or portrait mode, and it works even
when you hit refresh or rotate your device.
Please use this code freely. Credit is appreciated, but not required!
*/
function AutoViewport() {}
AutoViewport.setDimensions = function(requiredWidth, requiredHeight) {
/* Conditionally adds a default viewport tag if it does not already exist. */
var insertViewport = function () {
// do not create if viewport tag already exists
if (document.querySelector('meta[name="viewport"]'))
return;
var viewPortTag=document.createElement('meta');
viewPortTag.id="viewport";
viewPortTag.name = "viewport";
viewPortTag.content = "width=max-device-width, height=max-device-height,initial-scale=1.0";
document.getElementsByTagName('head')[0].appendChild(viewPortTag);
};
var isPortraitOrientation = function() {
switch(window.orientation) {
case -90:
case 90:
return false;
}
return true;
};
var getDisplayWidth = function() {
if (/iPhone|iPad|iPod/i.test(navigator.userAgent)) {
if (isPortraitOrientation())
return screen.width;
else
return screen.height;
}
return screen.width;
}
var getDisplayHeight = function() {
if (/iPhone|iPad|iPod/i.test(navigator.userAgent)) {
if (isPortraitOrientation())
return screen.height;
else
return screen.width;
}
// I subtract 180 here to compensate for the address bar. This is imperfect, but seems to work for my Android tablet using Chrome.
return screen.height - 180;
}
var adjustViewport = function(requiredWidth, requiredHeight) {
if (/Android|webOS|iPhone|iPad|iPod|BlackBerry/i.test(navigator.userAgent)){
var actual_height = getDisplayHeight();
var actual_width = getDisplayWidth();
var min_width = requiredWidth;
var min_height = requiredHeight;
var ratio = Math.min(actual_width / min_width, actual_height / min_height);
document.querySelector('meta[name="viewport"]').setAttribute('content', 'initial-scale=' + ratio + ', maximum-scale=' + ratio + ', minimum-scale=' + ratio + ', user-scalable=yes, width=' + actual_width);
}
};
insertViewport();
adjustViewport(requiredWidth, requiredHeight);
window.addEventListener('orientationchange', function() {
adjustViewport(requiredWidth, requiredHeight);
});
};
If you compare my code closely with the original code found in the question, you will notice a few differences. For example, I never rely on the viewport width or height. Instead, I rely on the screen object. This is important because as you refresh your page or rotate your screen, the viewport width and height can change, but screen.width and screen.height never change. The next thing you will notice is that I don't do the check for (ratio<1). When refreshing or rotating the screen, that check was causing inconsistency, so I removed it. Also, I included a handler for screen rotation.
Finally, I'd just like to say thank you to the person who created this question for laying the groundwork, which saved me time!
If you can't get consistent behavior across devices by changing the viewport meta tag, it's possible to zoom without changing the dimensions using CSS3 transforms:
if (ratio < 1) {
var box = document.getElementsByTagName('div')[0];
box.style.webkitTransform = 'scale('+ratio+')';
box.style.webkitTransformOrigin = '0 0';
}
console.log(box.offsetWidth); // always original width
console.log(box.getBoundingClientRect().width); // new width with scaling applied
Note I've omitted any vendor prefixes other than webkit here in order to keep it simple.
To center the scaled div you could use the translate tranforms:
var x = (actual_width - min_width * ratio) / 2;
var y = (actual_height - min_height * ratio) / 2;
box.style.webkitTransform = 'translateX('+x+'px) translateY('+y+'px) scale('+ratio+')';
box.style.webkitTransformOrigin = '0 0';
Replace your viewport with this :
<META NAME="viewport" CONTENT="width=device-width, height=device-height, initial-scale=1, user-scalable=no"/>
The user-scalable=0 here shall do the job for you.
This shall work for you.If it still doesn't work for we will have to extend the viewport so replace your viewport and add this:
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, target-densitydpi=medium-dpi, user-scalable=0" />
For your javascript error have a look at this link:
scale fit mobile web content using viewport meta tag
Set the height and width of the div's parent elements (html and body) to 100% and zero out the margin.
html, body {
margin: 0;
height: 100%;
width: 100%;
}
Next, because you want a border on the div you need to make sure that the border width is included when you specify the width / height of the element, to do this use box-sizing: border-box on the div.
Because you want a 3px top margin on the div relative positioning of the div will result in a height that is 3px too tall. To fix this use absolute positioning on the div and set top, left, and bottom to 0.
div {
position: absolute;
top: 3px;
left: 0;
bottom: 0;
box-sizing: border-box;
width: 100%;
border: 1px solid #f00;
background-color: #fdd;
}
Here's a working example.
UPDATE: I think I misunderstood the question. Here's a sample code that adjusts the "zoom" depending on the device's viewport
http://jpanagsagan.com/viewport/index2.html
Take note that I used jquery to append the meta tag as I am having issue using the vanilla append.
One thing I noticed is that if you hard-coded in the HTML and change it via JS, the document won't apply the correction (needs verification). I was able to change it via JS if there is no previous tag in the HTML, thus I used append.
You may play around with the ratio, but in the example I used width of the viewport divided by width of the div.
hope this helps.
UPDATE: I think I misunderstood the question. Here's a sample code that adjusts the "zoom" depending on the device's viewport
http://jpanagsagan.com/viewport/index2.html
Take note that I used jquery to append the meta tag as I am having issue using the vanilla append.
One thing I noticed is that if you hard-coded in the HTML and change it via JS, the document won't apply the correction (needs verification). I was able to change it via JS if there is no previous tag in the HTML, thus I used append.
You may play around with the ratio, but in the example I used width of the viewport divided by width of the div.
hope this helps.
I think Steven's should be the accepted answer.
In case it is helpful someone else, I would add the following 2 things to Steven's AutoViewport.js, in order to center the view within the viewport when the user is in landscape view:
Add "var viewport_margin = 0;" as the first line of code (as it's own line before "function AutoViewport() {}".
Add "viewport_margin = Math.abs(actual_width-(ratio*requiredWidth))/(actual_width*2)*100;" after the line that reads "document.querySelector('meta[name="viewport"]').setAttribute('content', 'initial-scale=' + ratio + ', maximum-scale=' + ratio + ', minimum-scale=' + ratio + ', user-scalable=yes, width=' + actual_width);"
Thanks for all those who posted to bring this solution to light.
UPDATE: In Android, my additions only appear to work with API 24+. Not sure why they aren't working with APIs 19-23. Any ideas?
I need to find the device-width of the mobile device.
Although we can specify the content
<meta name="viewport" content="width=device-width; user-scalable=no" />
But i need to programmatically obtain the device width to compute some logic in my application. How can I get the device width?
The viewport dimensions can be gathered via the window object:
var viewport = {
width : $(window).width(),
height : $(window).height()
};
//can access dimensions like this:
//viewport.height
Though you won't always get perfect results, different devices behave differently and this gives the viewport dimensions, not the screen dimensions.
Alternatively you could check the width of a data-role="page" element to find the device-width (since it's set to 100% of the device-width):
var deviceWidth = 0;
$(window).bind('resize', function () {
deviceWidth = $('[data-role="page"]').first().width();
}).trigger('resize');
Not sure that the solution proposed works as expected. Are you sure you get the real device-width?
I'm using the following code in my app and it works fine:
function effectiveDeviceWidth() {
var deviceWidth = window.orientation == 0 ? window.screen.width : window.screen.height;
// iOS returns available pixels, Android returns pixels / pixel ratio
// http://www.quirksmode.org/blog/archives/2012/07/more_about_devi.html
if (navigator.userAgent.indexOf('Android') >= 0 && window.devicePixelRatio) {
deviceWidth = deviceWidth / window.devicePixelRatio;
}
return deviceWidth;
}
Hope it can help someone!
Im working on a a mobile online-store And got stuck while implementing the product zoom function
After clicking an Image "user-scalable" is allowed and maximum-scale is set to 10.0
When the user zooms in on the product with a pinch gesture, everything works fine.
But after closing the zoomed Image the scale is not reset to 1.0.
Is there a way to reset the scale value of the viewport dynamically.
The "initial-scale" seems not to work, neither does reseting the "minimum-scale" and "maximum-scale" to 1.0
The problems occurs on iPhone / iPad
There seems to be a solution, but i don't know to which element i should apply the on this post:
How to reset viewport scaling without full page refresh?
"You need to use -webkit-transform: scale(1.1); webkit transition."
But I don't know to which element the style is applied.
Here is some code to illustrate the Problem.
In the meta Tag for the viewport looks like this:
<meta name="viewport" content="user-scalable=no, width=device-width, height=device-height, minimum-scale=1.0, maximum-scale=1.0" />
the rest of the page Looks like this:
<div id="page">
<img src="images/smallProductImage.jpg">
</div>
<div id="zoom">
<div class="jsZoomImageContainer"></div>
</div>
and this is the javascript::
zoom:{
img: null,
initialScreen:null,
load:function(src){
//load the image and show it when loaded
showLoadingAnimation();
this.img = new Image();
this.img.src = src;
jQuery(this.img).load(function(){
zoom.show();
});
},
show:function(){
var screenWidth, screenHeight, imageWidth, imageHeight, scale, ctx;
hideLoadingAnimation();
jQuery("#page").hide();
jQuery("#zoom").show();
jQuery(".jsZoomImageContainer").empty();
this.initialScreen =[jQuery(window).width(), jQuery(window).height()]
jQuery(".jsZoomImageContainer").append(this.img);
imageWidth = jQuery(this.img).width();
imageHeight = jQuery(this.img).height();
scale = this.initialScreen[0] / imageWidth ;
jQuery(this.img).width(imageWidth * scale)
jQuery(this.img).height(imageHeight * scale)
jQuery(".jsZoomImageContainer").click(function(){
zoom.hide();
});
jQuery('meta[name="viewport"]',"head").attr("content","user-scalable=yes, initial-scale:1.0, minimum-scale=1.0, maximum-scale=10.0")
},
hide:function(){
jQuery(".jsZoomImageContainer").empty();
jQuery('meta[name="viewport"]',"head").attr("content","user-scalable=no, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0")
jQuery("#zoom").hide();
jQuery("#page").show();
this.img = null;
this.initialScreen = null;
}
}
jQuery("#page img").click(function(){
zoom.load("images/bigProductImage.jpg");
});
According to ppk, this technique for viewport manipulation works on all modern browsers except for Firefox:
<meta id="testViewport" name="viewport" content="width = 380">
<script>
if (screen.width > 740) {
var mvp = document.getElementById('testViewport');
mvp.setAttribute('content','width=740');
}
</script>
Seems like the key is setting an id attribute in the meta tag so you can select it easily with JS and replace the value of the content attribute.
It works in all modern browsers. I have done it in a few websites and all work fine.
But resetting is not a solution to the problem. You need to properly change scale and viewport width when circumstances change.
You need to change it when orientation changes and when screen size changes and of course on load when screen size is detected. If you get values for current width, you can calculate the scale. (By the way, when orientation is 90 or -90, you should take height as width).
For example,
If your main container is 960px in width, and w_width is the current width you get dynamically.
scale=100/100/(960/w_width);
scale=scale.toFixed(2) ;
jQuery('meta[name=viewport]').attr('content', "width="+w_width+", initial-scale="+scale);