How to Circumscribe a square in a circle CSS [duplicate] - css

Question

I've looked into this a fair bit but can't seem to find a good, solid answer to find how to make a responsive circle around a div element of variable height.
It's easy to make a simple responsive circle using vw units.
<div style="height:20vw; width:20vw"></div>
However, I'm looking to use a min-height of an element and have a circle around this div.
Another way to create a responsive circle is using something like the snippet below, but again I can't adapt this to work for a variable height (again, I can't use vh units as the div will change in height.
.square {
position: relative;
width: 10%;
background: gray;
border-radius: 50%;
}
.square:after {
content: "";
display: block;
padding-bottom: 100%;
}
.content {
position: absolute;
width: 100%;
height: 100%;
}
<div class="square">
<div class="content">
</div>
</div>
I am trying to create something like the below, where the circle will never cut into the corners of the div (with around a 10px padding). I personally was trying to avoid javascript and would have preferred a css only approach, but it seems it's unavoidable. Maybe the only solution is to use a jquery to calculate the height of the element in order to apply this to a wrapper element?
I was playing around with this:
.square {
position: absolute;
top: 50%;
display: inline-block;
left: 50%;
transform: translate(-50%, -50%);
min-height: 100px;
border-radius: 50%;
background: url('https://i.imgur.com/2dxaFs9_d.webp?maxwidth=640&shape=thumb&fidelity=medium');
background-size: 100% 100%;
padding: 20px;
}
.content {
width: 300px;
min-height: 100px;
background: tomato;
}
<div class="square">
<div class="content">
Hello!<br>
<br><br><br>This has a variable height but fixed width<br><br><br>Hello
</div>
</div>

Answer 1

Clip-path can easily do this if you consider solid coloration.
Resize the element and the circle will follow:
.box {
width: 200px;
height: 200px;
overflow: hidden;
resize: both;
background: blue;
box-shadow: 0 0 0 200vmax red;
clip-path: circle(71%);
margin: 100px auto;
}
<div class="box"></div>
Related question to understand the magic number 71%: clip-path:circle() radius doesn't seem to be calculated correctly
To use an image we can consider pseudo elements. You can also rely on calc() to add the offset:
.box {
width: 200px;=
resize: both;
clip-path: circle(calc(71% + 10px));
margin: 100px auto;
position: relative;
font-size:35px;
color:#fff;
}
/* the background layer */
.box::before {
content:"";
position: absolute;
z-index:-1;
top:0;
left:0;
right:0;
bottom:0;
background:blue;
}
/* the image layer */
.box::after {
content:"";
position: fixed; /* to make sure the image cover all the screen */
z-index:-2;
top:0;
bottom:0;
left:0;
right:0;
background:url(https://picsum.photos/id/1015/1000/1000) center/cover no-repeat;
}
<div class="box" contenteditable="true"> Edit this<br>text </div>

Answer 2

I tried my hardest to figure this out with pure css. Though the problem with css I could not figure out how to calculate the diameter of the circle based on the content div size; the length from top left corner to bottom right corner of the variable height div.
I'm not sure if can be done using the calc() css function.
But I did manage to do it with a little jquery (which could easily be changed to pure javascript if you are not using jquery).
See working resizable example below (follow my comments in code)
Note: If you are using internet explorer the resizable demo content div will not resize.
// circumscriber for variable size divs
function circumscriber() {
// for each variable size div on page
$(".variable-size").each(function() {
// get the variable size div content width and height
let width = $(this).outerWidth();
let height = $(this).outerHeight();
// get the diameter for our pefect circle based on content size
let diameter = Math.sqrt(width ** 2 + height ** 2);
// extra 15 pixel circle edge around variable size div
let edge = 15;
// add current circle size width css
$('.circle', this).css({
'width': (diameter + (edge * 2)) + 'px'
})
});
}
// run the circumscriber (you might wana do this on ready)
circumscriber();
// if the window is resized responsively
$(window).on('resize', function() {
circumscriber();
});
// for demo purpose to fire circumscriber when resizing content
// not needed for real thing
$('.content').on('input', function() {
this.style.height = "";
this.style.height = ( this.scrollHeight - 30 ) + "px";
circumscriber();
}).on('mouseup', function() {
circumscriber();
});
/* variable size container to be circumscribed by circle */
/* none of these styles are required, this just to center the variable size div in the window for demo purposes */
.variable-size {
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}
/* resizable text area for demo */
/* again not needed */
.variable-size .content {
padding: 15px;
background: #fff;
resize: both;
overflow: auto;
color: #000;
border: none;
width: 200px;
font-weight: bold;
}
.variable-size .content:focus {
outline: 0;
}
/* child circle div css */
.variable-size .circle {
position: absolute;
background-image: url('https://i.imgur.com/2dxaFs9_d.webp?maxwidth=640&shape=thumb&fidelity=medium');
background-position: center center;
z-index: -1;
border-radius: 50%;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
transition: all 0.5s ease;
width: 0;
}
/* fast way to make circle height the same as current width */
.variable-size .circle:before {
display: block;
content: '';
width: 100%;
padding-top: 100%;
}
/* demo window css */
HTML,
BODY {
height: 100%;
min-height: 100%;
background: black;
position: relative;
font-family: "Lucida Console", Courier, monospace;
}
<div class="variable-size">
<textarea class="content" rows="1" placeholder="TYPE TEXT OR RESIZE ME ↘"></textarea>
<div class="circle"></div>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
See jsfiddle here... https://jsfiddle.net/joshmoto/6d0zs7uq/

Answer 3

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.arc(100, 75, 50, 0, 2 * Math.PI);
ctx.stroke();
Source: https://www.w3schools.com/

Answer 4

You could use flex display and insert empty flex-items around the inner div and use flex-basis to fix their width.
Try this
.square {
display: flex;
justify-content: center;
align-items: center;
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
min-height: 100px;
border-radius: 50%;
background: black;
background-size: 100% 100%;
padding: 20px;
}
.content {
width: 300px;
min-height: 100px;
background: tomato;
}
.emptyDiv {
flex-basis: 120px
}
<div class="square">
<div class="emptyDiv"></div>
<div class="content">
Hello!<br>
<br><br><br>This has a variable height but fixed width<br><br><br>Hello
</div>
<div class="emptyDiv"></div>
</div>