How to position an SVG circle along another circle's path

user_1583032 0
Viewed 1340

I'm building a Gauge chart in a presentational component in React.

I just need to pass it a percentage and let the component do the rest. I can't use any animations because I'm taking a screenshot of the component to place the image in a Powerpoint presentation.

Here's a screenshot of what I'm trying to do:

enter image description here

As you can see in my code snippet, the circle <marker> is being positioned at the end of the grey <path> instead of at the end of the green <path>. How could I position the circle so it sits at the stroke-linecap of the green <path> as in the image above?

Here's the HTML code I have so far:

<div style="width:400px">
  <svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
    <defs>
      <marker
        id="dot"
        viewBox="0 0 10 10"
        refX="4"
        refY="4"
        markerWidth="4"
        markerHeight="4"
      >
        <circle
          cx="4"
          cy="4"
          r="2"
          fill="#FFFFFF"
          stroke="#008000"
          stroke-width="2"
        />
      </marker>
    </defs>
    <path d="M20,60a35,35 0 1,1 60,0" stroke="#D3D7DB" stroke-width="4" fill="none" stroke-linecap="round"></path>
    <path d="M20,60a35,35 0 1,1 60,0" stroke="#008000" stroke-width="6" pathLength="100" fill="none" stroke-linecap="round" stroke-dasharray="75 35" marker-end="url(#dot)"></path>
  </svg>
</div>

svg html javascript
2 Answers

You can do it all in SVG by setting pathLength and using animationMotion to position the circle.

Some JavaScript and a W3C standard Web Component (supported in all modern Browsers) help in putting multiple gauges on screen and making them dynamic.

<svg-gauge value="35" color="red"></svg-gauge>
<svg-gauge value="50" color="orange"></svg-gauge>
<svg-gauge value="75" color="green"></svg-gauge>
<script>
  customElements.define("svg-gauge", class extends HTMLElement {
    connectedCallback() {
      let arc = "M20,60a35,35 0 1,1 60,0";
      let col = this.getAttribute("color")||"green";
      this.innerHTML = 
      `<input type="range" min="0" max="100" step="5" value="0"`+ // delete 2 lines
      ` oninput="this.parentNode.percent=this.value" /><br>`+ // just for demo
`<svg viewbox="0 0 100 100">
  <path d="${arc}" stroke="grey" stroke-width="6" fill="none" 
        stroke-linecap="round"></path>
  <path id="P" d="${arc}" stroke="${col}" stroke-width="8" pathLength="100" 
        fill="none" stroke-linecap="round" stroke-dasharray="75 35"></path>
  <circle cx="0" cy="0" fill="#fff" r="4" stroke="${col}" stroke-width="3">
     <animateMotion dur="0.5s" keyPoints="0;0.75" 
                    fill="freeze" keyTimes="0;1" calcMode="linear" path="${arc}">
     </animateMotion></circle>
  <text x="50%" y="40%" text-anchor="middle">XXX</text>
</svg>`;
      this.style.display='inline-block';
      this.percent = this.getAttribute("value");
    }
    set percent(val = 0) {
      this.setAttribute("value", val);
      let dash = val + " " + (105 - val);
      this.querySelector("#P").setAttribute('stroke-dasharray', dash);
      this.querySelector("animateMotion").setAttribute('keyPoints', '0;'+val/100);
      this.querySelector("text").innerHTML =`${val} %`;
      this.querySelector("animateMotion").beginElement();
      this.querySelector("input").value = val;
    }
  })
</script>

user_25208000

I went ahead and accepted Danny '365CSI' Engelman's answer above, but just in case anyone wants to do this without the animations here is how I ended up implementing it:

<div style="width:400px">
  <svg viewBox="0 -10 100 100" xmlns="http://www.w3.org/2000/svg">
    <path d="M20,60a35,35 0 1,1 60,0" stroke="#D3D7DB" stroke-width="4" fill="none" stroke-linecap="round"></path>
    <path d="M20,60a35,35 0 1,1 60,0" stroke="#008000" stroke-width="6" pathLength="100" fill="none" stroke-linecap="round" stroke-dasharray="50 85"></path>
    <circle
          cx="0"
          cy="0"
          r="6"
          stroke-width="6"
          fill="#FFFFFF"
          stroke="#008000"
        >
          <animateMotion
            begin="0s"
            dur="infinite"
            repeatCount="infinite"
            keyPoints="0.5;0.5"
            fill="freeze"
            keyTimes="0;1"
            calcMode="linear"
            path="M20,60a35,35 0 1,1 60,0"
          ></animateMotion>
        </circle>
  </svg>
</div>

user_15830320
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