HTML5 / CSS3 Circle with Partial Border

Question

Is it possible to create a circle using only HTML5 / CSS3 which has a border that only goes part way around the circle? If not, what techniques can I use to accomplish this effect? I would prefer to use pure DOM elements, but if I have to I can draw on canvas or spin up an SVG.

Answer 1

Yes, it is possible - see this:

demo

.circle {
  position: relative;
  margin: 7em auto;
  width: 16em;
  height: 16em;
  border-radius: 50%;
  background: lightblue;
}

.arc {
  overflow: hidden;
  position: absolute;
  /* make sure top & left values are - the width of the border */
  /* the bottom right corner is the centre of the parent circle */
  top: -1em;
  right: 50%;
  bottom: 50%;
  left: -1em;
  /* the transform origin is the bottom right corner */
  transform-origin: 100% 100%;
  /* rotate by any angle */
  /* the skew angle is 90deg - the angle you want for the arc */
  transform: rotate(45deg) skewX(30deg);
}

.arc:before {
  box-sizing: border-box;
  display: block;
  border: solid 1em navy;
  width: 200%;
  height: 200%;
  border-radius: 50%;
  transform: skewX(-30deg);
  content: '';
}

<div class='circle'>
  <div class='arc'></div>
</div>

Answer 2

It's possible.

• Draw two circles using border-radius one on top of another.
• Make one or more arc of both circles transparent by changing border-color.
• Use transform to rotate the second circle and you will have the arc of the size you need.

Here is the demo: http://jsfiddle.net/kJXwZ/2/

.wrapper {
  position: relative;
  margin: 20px;
}

.arc {
  position: absolute;
  top: 0;
  left: 0;
  width: 100px;
  height: 100px;
  border-radius: 100%;
  border: 1px solid;
}

.arc_start {
  border-color: transparent red red red;
  -webkit-transform: rotate(45deg);
  -moz-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  -o-transform: rotate(45deg);
  transform: rotate(45deg);
}

.arc_end {
  border-color: red red red transparent;
  -webkit-transform: rotate(75deg);
  -moz-transform: rotate(75deg);
  -ms-transform: rotate(75deg);
  -o-transform: rotate(75deg);
  transform: rotate(75deg);
}

<div class="wrapper">
  <div class="arc arc_start"></div>
  <div class="arc arc_end"></div>
</div>

Answer 3

This uses JavaScript as well, so it breaks from the original requirement :(
.. it does however deliver

There is a >> demo << here

@gkond Thanks, I derived this from your answer

// create a circle using HTML5 / CSS3 / JS which has a border that only goes part-way around
// the circle .. and which can be smoothly animated from 0% to 100% around the circle

// this solution allows for animation and still results in relatively clean code
// we use four quarter-circles, all hidden away behind a white square to start with..
// all four are rotated out clockwise, and each quarter will stop at it's own maximum:
// q1 at 25%, q2 at 50% .. etc. once we reach a value at or over 25%, all four quarters
// should be out from behind the white square, and we can hide it.. it needs to be
// hidden if we display a value over 75%, or else q4 will end up going in behind it again
// .. also, since the top border will usually sit between the angles of  -45 to 45, we
// rotate everything by an extra -45 to make it all line up with the top nicely

var fromHidden = -90;

// utility function to align 0 degrees with top
// takes degrees and returns degrees - 45
function topAlign(degrees) {
  return degrees - 45
};

// utility function to rotate a jQuery element
// takes element and the degree of rotation (from the top) 
function rotate(el, degrees) {
  var degrees = topAlign(degrees || 0);
  el.css(
    'transform', 'rotate(' + degrees + 'deg)',
    '-webkit-transform', 'rotate(' + degrees + 'deg)',
    '-moz-transform', 'rotate(' + degrees + 'deg)',
    '-ms-transform', 'rotate(' + degrees + 'deg)',
    '-o-transform', 'rotate(' + degrees + 'deg)'
  )
}

// function to draw semi-circle
// takes a jQuery element and a value (between 0 and 1)
// element must contain four .arc_q elements
function circle(el, normalisedValue) {
  var degrees = normalisedValue * 360; // turn normalised value into degrees
  var counter = 1; // keeps track of which quarter we're working with
  el.find('.arc_q').each(function() { // loop over quarters..
    var angle = Math.min(counter * 90, degrees); // limit angle to maximum allowed for this quarter
    rotate($(this), fromHidden + angle); // rotate from the hiding place
    counter++; // track which quarter we'll be working with in next pass over loop
  });
  if (degrees > 90) { // hide the cover-up square soon as we can
    el.find('.arc_cover').css('display', 'none');
  }
}

// uses the the circle function to 'animate' drawing of the semi-circle
// incrementally increses the value passed by 0.01 up to the value required
function animate(el, normalisedValue, current) {
  var current = current || 0;
  circle(el, current);
  if (current < normalisedValue) {
    current += 0.01;
    setTimeout(function() {
      animate(el, normalisedValue, current);
    }, 1);
  }
}

// kick things off ..
animate($('.circle'), 0.69);

.circle {
  position: relative;
  margin: 20px;
  width: 120px;
  height: 120px;
}

.arc_q {
  position: absolute;
  top: 0;
  left: 0;
  width: 100px;
  height: 100px;
  border-radius: 50%;
  border: 10px solid;
  border-color: transparent green transparent transparent;
  transform: rotate(-45deg);
  -webkit-transform: rotate(-45deg);
  -moz-transform: rotate(-45deg);
  -ms-transform: rotate(-45deg);
  -o-transform: rotate(-45deg);
}

.arc_cover {
  position: absolute;
  top: 0;
  left: 0;
  width: 60px;
  height: 60px;
  background-color: white;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="circle">
  <div class="arc_q"></div>
  <div class="arc_q"></div>
  <div class="arc_q"></div>
  <div class="arc_q"></div>
  <div class="arc_cover"></div>
</div>

Answer 4

Conic gradient solution (works for any degree):

:root{
--degree:80deg;
--color:red;
}

.a{
  height:200px;
  width:200px;
border-radius:50%;
background: conic-gradient(
     var(--color) var(--degree), transparent calc(var(--degree) + 0.5deg) 100%);

}

.b{
  height:84%;
  width:84%;
  top:8%;
  left:8%;
  position:relative;
  border-radius:50%;
  background:#D3D3D3;
}

<div class ="a">
    <div class="b">
</div>