Develop Reference

Proportional width div with 100% height (without JS?) [duplicate]

I need to maintain the width of an element as a percentage of its height. So as the height changes, the width is updated.
The opposite is achievable by using a % value for padding-top, but padding-left as a percentage will be a percentage of the width of an object, not its height.
So with markup like this:
<div class="box">
<div class="inner"></div>
</div>
I'd like to use something like this:
.box {
position: absolute;
margin-top: 50%;
bottom: 0;
}
.inner {
padding-left: 200%;
}
To ensure the box's aspect ratio is maintained according to it's height. The height is fluid because of it's % margin - as the window's height changes, the box's height will too.
I know how to achieve this with JavaScript, just wondering if there's a clean CSS-only solution?

You can use an image that has the desired proportions as to help with proportional sizing (images can be scaled proportionally by setting one dimension to some value and other to auto). The image does not have to be visible, but it must occupy space.
.box {
position: absolute;
bottom: 0;
left: 0;
height: 50%;
}
.size-helper {
display: block;
width: auto;
height: 100%;
}
.inner {
position: absolute;
top: 0;
bottom: 0;
left: 0;
right: 0;
background: rgba(255, 255, 153, .8);
}
<div class="box">
<img class="size-helper" src="//dummyimage.com/200x100/999/000" width="200" height="100">
<div class="inner">
1. box has fluid height<br>
2. img has 2:1 aspect ratio, 100% height, auto width, static position<br>
2.1 it thus maintains width = 200% of height<br>
2.2 it defines the dimensions of the box<br>
3. inner expands as much as box
</div>
</div>
In the above example, box, inner and helper are all same size.

You can use vh units for both height and width of your element so they both change according to the viewport height.
vh
1/100th of the height of the viewport. (MDN)
DEMO
.box {
position: absolute;
height:50vh;
width:100vh;
bottom: 0;
background:teal;
}
<div class="box"></div>

There is another, more efficient way to achieve constant aspect ratio according to height.
You can place an empty svg so you dont have to load an external image.
HTML code:
<svg xmlns="http://www.w3.org/2000/svg"
height="100"
width="200"
class='placeholder-svg'
/>
CSS code:
.placeholder-svg {
width: auto;
height: 100%;
}
Change width/height to achieve desired aspect ratio.
Keep in mind, the svg might overflow.
http://www.w3.org/2000/svg is just a namespace. It doesn't load anything.
If you change placeholder-svg class to:
.placeholder-svg {
width: 100%;
height: auto;
}
then height is adjusted according to width.
Demo 1 Width is adjusted according to height and 2:1 aspect ratio.
Demo 2 same as above, but you can resize easily (uses React)

The CSS trick you wrote, works pretty well to keep ratio width / height on an element.
It is based on the padding property that, when its value is in percent, is proportional to parent width, even for padding-top and padding-bottom.
There is no CSS property that could set an horizontal sizing proportionally to the parent height.
So I think there is no clean CSS solution.

As of 2021 there is a property called aspect-ratio.
Most browsers support it
div {
border: 1px solid;
margin: 8px;
}
.box {
width: 100px;
min-height: 100px;
resize: horizontal;
overflow: auto;
}
.inner1 {
aspect-ratio: 1/1;
}
.inner2 {
aspect-ratio: 3/1;
}
<div class="box">
<div class="inner1"></div>
<div class="inner2"></div>
</div>
Run this snippet and resize the outer div manually to see the inner divs behavior

I can't find a pure CSS solution. Here's a solution using CSS Element Queries JavaScript library.
var aspectRatio = 16/9;
var element = document.querySelector('.center');
function update() {
element.style.width = (element.clientHeight * aspectRatio) + 'px';
}
new ResizeSensor(element, update);
update();
CodePen demo!

Vertically align 50% of the viewport [duplicate]

This question already has answers here:
Vertically center in viewport using CSS
(4 answers)
Closed 9 years ago.
I am trying to vertically align a div to 50% of the viewport, no matter how long the document is.
You can see an example here http://fancyapps.com/fancybox/#examples

Box offsets properties can be used to obtain this effect.
This property specifies how far an absolutely positioned box's top
margin edge is offset below the top edge of the box's containing
block.
Source: http://www.w3.org/TR/CSS2/visuren.html#position-props
jsfiddle
CSS
#centered {
position: fixed;
top: 0;
bottom: 0;
right: 0;
left: 0;
margin: auto;
height: 200px; /* arbitrary */
width: 600px; /* arbitrary */
background-color: grey;
}

Here is a jQuery example that will center a div regardless of it's height and width.
DEMO http://jsfiddle.net/kevinPHPkevin/dzSPN/120/
function animateHight(newHeight){
$('div#centered').animate({'height': newHeight, 'margin-top': -newHeight/2}, 600, function(){animateWidth(100);animateHight(100);});
}
function animateWidth(newWidth){
$('div#centered').animate({'width': newWidth, 'margin-left': -newWidth/2}, 600);
}

How to place a div inside a bigger scrollable div at particular position

I have a div with height = 10*screen-height.
I want to add another smaller div to it with height = screen height
Assuming that I can add 10 such smaller div's onto the bigger div, I want to add this div at particular position on the bigger div. Say starting from 4*screenheight pixel. How do I do that using jQuery?

Presumably you already have the screen height stored, and the two divs created at the correct heights, so:
$(inner_div).css('position', 'relative').css('top', 4*screen_height);
You may not need position:relative in your style if it's in your css already

See here how you can access and manipulate the body's height and the big div's inners afterwards;
JSfiddle
HTML
<div id="biggy">
<div class="smally">Smally :)</div>
<div class="smally">Smally 2, don't forget me :D</div>
</div>
CSS
html, body {
height: 100%;
padding: 0px;
margin: 0px;
}
#biggy {
width: 200px;
background-color: orange;
position: relative;
}
.smally {
width: 100%;
background-color: blue;
color: white;
text-align: center;
position: absolute;
}
JavaScript
$(document).ready(function() {
var bh = $('body').height();
var smally_offset = (bh / 10);
// Set biggy to be the body's height
$('#biggy').css('height', bh);
// Make all smallies 10% of the set height
$('.smally').css('height', smally_offset);
// Handle the different smallies :)
$('.smally:nth-child(1)').css('top', smally_offset * 0);
$('.smally:nth-child(2)').css('top', smally_offset * 1);
});

Vertical middle alignment of image within div? [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
vertical alignment of image inside a div
OK, this what I'm trying to do :
I'm having an empty div (a box), with almost no height.
I'm making an AJAX request to load some content into it.
Before loading the content, I want to display in a typical "ajax loading" rotating gif.
I've managed to :
Center the img horizontally (by putting it inside another div with text-align:center;)
What is left :
Be able to give some height to that empty div. (easy)
Vertically align the image, so that it appears on the very center of the box. (I've got absolutely no idea how to do this. I'm currently setting an upper margin, which works for one particular box, but which wouldn't work if the box already has some different height...)
How would you go about it?? (Any possible idea is acceptable. CSS/Javascript whatever...)

http://jsfiddle.net/teresko/5mG2y/
The basic idea is the use display: table-cell; and then vertical-align: middle;
the HTML
<div class="container">
<div class="holder">
<img class="stuff" src="path/to/image.png">
</div>
</div>
the CSS:
.container{
/* the container in which image is placed */
height: 300px;
margin: 0 auto;
width: 200px;
}
.holder{
display: table-cell;
width: 100%;
vertical-align: middle;
height: inherit;
}
.stuff{
display: block;
}
This way the placement of image will not depend on dimensions of container. It also can be adjusted to be in horizontal center too. All you have to do is to add .stuff{ margin: 0 auto;}.

Don't forget that table-cell is not the correct usage. You don't want images to be trated as table cells, since table cells should only contain table data.
Just raising a caution flag. Stick to the semantics.
it's better to use the answer from that other thread.
This:
#container { position: relative; }
#container img {
position: absolute;
left: 50%;
top: 50%;
margin-top: /* -1/2 the height of the image */
margin-left: /* -1/2 the width of the image */
}
Good luck!

With jQuery
//HTML
<div><img src="loader.gif" class="loader" alt="Loader" /></div>
//JS
$.fn.centeringIn = function(){
var pere = this.parent();
(pere.css("position") == 'static') ? pere.css("position","relative"):pere.css("position");
this.css({
'position' : 'absolute',
'top' : ( pere.height() - this.height() )/2+'px',
'left' : ( pere.width() - this.width() )/2+'px'
});
}
$(document).ready( function() {
$('.loader').centeringIn();
});

Add some margin-top to the image style so that it is aligned in the middle of the div. Say your div is 50px height and your image has a height of 5px. Then make your margin-top 20px to put it in the middle.

Scale a div to fit in window but preserve aspect ratio

How can I scale a div to fit inside the browser view port but preserve the aspect ratio of the div. How can I do this using CSS and/or JQuery?
Thanks!

You don't need javascript for this. You can use pure CSS.
A padding-top percentage is interpreted relative to the containing block width. Combine it with position: absolute on a child element, and you can put pretty much anything in a box that retains its aspect ratio.
HTML:
<div class="aspectwrapper">
<div class="content">
</div>
</div>
CSS:
.aspectwrapper {
display: inline-block; /* shrink to fit */
width: 100%; /* whatever width you like */
position: relative; /* so .content can use position: absolute */
}
.aspectwrapper::after {
padding-top: 56.25%; /* percentage of containing block _width_ */
display: block;
content: '';
}
.content {
position: absolute;
top: 0; bottom: 0; right: 0; left: 0; /* follow the parent's edges */
outline: thin dashed green; /* just so you can see the box */
}
The display: inline-block leaves a little extra space below the bottom edge of the .aspectwrapper box, so another element below it won't run flush against it. Using display: block will get rid of it.
Thanks to this post for the tip!
Another approach relies on the fact that browsers respect an image's aspect ratio when you resize only its width or height. (I'll let google generate a 16x9 transparent image for demonstration purposes, but in practice you would use your own static image.)
HTML:
<div class="aspectwrapper">
<img class="aspectspacer" src="http://chart.googleapis.com/chart?cht=p3&chs=160x90" />
<div class="content">
</div>
</div>
CSS:
.aspectwrapper {
width: 100%;
position: relative;
}
.aspectspacer {
width: 100%; /* let the enlarged image height push .aspectwrapper's bottom edge */
}
.content {
position: absolute;
top: 0; bottom: 0; right: 0; left: 0;
outline: thin dashed green;
}

Thanks to Geoff for the tip on how to structure the math and logic. Here's my jQuery implementation, which I'm using to size a lightbox so it fills the window:
var height = originalHeight;
var width = originalWidth;
aspect = width / height;
if($(window).height() < $(window).width()) {
var resizedHeight = $(window).height();
var resizedWidth = resizedHeight * aspect;
}
else { // screen width is smaller than height (mobile, etc)
var resizedWidth = $(window).width();
var resizedHeight = resizedWidth / aspect;
}
This is working well for me right now across laptop and mobile screen sizes.

I have a different pure HTML/CSS approach which does not rely on padding or absolute positioning. Instead it uses em units and relies on the CSS min() function plus a little bit of math.
Imagine that we want a viewport div with 16:9 aspect ratio which always fits the browser window and is centered in the axis with excess space. Here's how we can accomplish that:
HTML
<body>
<div class="viewport">
<p>
This should be a 16:9 viewport that fits the window.
</p>
</div>
</body>
CSS
body {
width: 100vw;
height: 100vh;
margin: 0;
display: flex;
justify-content: center;
align-items: center;
background-color: white;
font-size: min(1vw, 1.778vh);
}
div.viewport {
width: 100em;
height: 56.25em;
background-color: lightblue;
}
div.viewport > p {
font-size: 3em;
text-align: center;
}
You can experiment with this in a sample JSFiddle here.
The secret sauce is in the body font-size. It should be set to min(1vw, Avh), where A is the aspect ratio you want the div to have, i.e. width / height. In the example above we're using 1.778, which is approximately 16 / 9.
In CSS, em units are based on the font-size of the element, which is inherited from parent element if not explicitly set. For your viewport div, set the width to 100em (NOT rem) and the height to Iem, where I is the inverse of the aspect ratio expressed as a percentage, i.e. 100 / A or 100 * height / width. In the example above we're using 56.25, which is 100 * 9 / 16.
One bonus of this approach is that all of your nested elements may also use em units so that they always scale precisely with the size of the viewport. You can see this used on the p element in the example.
Note that as an alternative to the above, you may set the font-size on your html element and use rem units everywhere. CSS rem units are similar to em units but always relative to the root element's font-size.

Javascipt:
//Responsive Scaling
let outer = document.getElementById('outer'),
wrapper = document.getElementById('wrap'),
maxWidth = outer.clientWidth,
maxHeight = outer.clientHeight;
window.addEventListener("resize", resize);
resize();
function resize(){
let scale,
width = window.innerWidth,
height = window.innerHeight,
isMax = width >= maxWidth && height >= maxHeight;
scale = Math.min(width/maxWidth, height/maxHeight);
outer.style.transform = isMax?'':'scale(' + scale + ')';
wrapper.style.width = isMax?'':maxWidth * scale;
wrapper.style.height = isMax?'':maxHeight * scale;
}
HTML:
<div id="wrap">
<div id="outer">
{{ fixed content here }}
</div>
</div>
Styling:
/* Responsive Scaling */
#wrap {
position: relative;
width: 1024px;
height: 590px;
margin: 0 auto;
}
#outer {
position: relative;
width: 1024px;
height: 590px;
transform-origin: 0% 0%;
overflow: hidden;
}

This is possible with JQuery and a bit of maths.
Use JQuery to get the view ports width and height as well as the divs current dimensions.
$(document).width();
Calculate the divs current aspect ratio. eg width/height
You need a bit of logic to determine whether to set the width or height first, then use the initial ratio to calculate the other side.

jQuery has a plugin that grows an object until one of it's sides reaches a certain px-value. Coupling this will the viewport's height, you could expand any element to that size: jQuery MaxSide.