How to make an SVG “line” with a border around it?

StackOverflow https://stackoverflow.com/questions/8845426

  •  27-10-2019
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Question

I have a little svg widget whose purpose is to display a list of angles (see image).

Right now, the angles are line elements, which only have a stroke and no fill. But now I'd like to have an "inside fill" color and a "stroke/border" around it. I'm guessing the line element can't handle this, so what should I use instead?

Notice that the line-endcap of the line's stroke is rounded. I'd like to maintain this effect in the solution.

Angle Line

<svg height="160" version="1.1" viewBox="-0.6 -0.6 1.2 1.2" width="160" xmlns="http://www.w3.org/2000/svg">
  <g>
    <g>
      <circle class="sensorShape" cx="0" cy="0" fill="#FFF" r="0.4" stroke="black" stroke-width="0.015"/>
      <line stroke="black" stroke-width="0.015" x1="0" x2="0" y1="-0.4" y2="0.4"/>
      <line stroke="black" stroke-width="0.015" x1="-0.4" x2="0.4" y1="0" y2="0"/>
    </g>
    <g class="lsNorthAngleHandsContainer">
      <line data-angle="348" stroke="red" stroke-linecap="round" stroke-width="0.04" transform="rotate(348)" x1="0" x2="0" y1="0" y2="-0.4"/>
      <text font-size="0.08" transform="translate(-0.02316467632710395,-0.45125904029352226)">
        348
      </text>
    </g>
  </g>
</svg>
Was it helpful?

Solution

Add a second line, with same coordinates but thinner line width:

<g class="lsNorthAngleHandsContainer">
  <line data-angle="348" stroke="red" stroke-linecap="round" stroke-width="0.04" transform="rotate(348)" x1="0" x2="0" y1="0" y2="-0.4"/>
  <line data-angle="348" stroke="yellow" stroke-linecap="round" stroke-width="0.025" transform="rotate(348)" x1="0" x2="0" y1="0" y2="-0.4"/>

OTHER TIPS

It looks like your line is opaque, so you can just draw a thin line with the "inside" color on top of the thicker line with the "outside" color.

You could use a rect with rounded corners, but the math changes a bit:

  <rect data-angle="348" stroke="red" stroke-linecap="round" stroke-width="0.02" fill="#FF0" transform="rotate(348, 0, 0)" x="-0.02"  y="-0.4" width=".06" height=".4" rx=".03" ry=".03"/>

http://jsfiddle.net/RNAuP/

I found elegant solution inspired by illustration to W3C article about filling and stroking. Basically, you move path to definitions and use this definition to draw two elements:

<svg width="200" height="200" viewBox="0 0 100 100">
    <defs>
        <line id="line1" x1="25" x2="75" y1="25" y2="75"/>
    </defs>
    <use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#line1" class="stroke"></use>
    <use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#line1" class="line"></use>
</svg>

By using <defs> and <use> you can change only path element to update both lines. JSFiddle demo

You can also do it with a path, even though it's tricky around the round bits:

<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd" [
  <!-- I often use entities to be able to change lot of numbers at once in static SVG, also kind of makes the paths more readable.
       Obvisouly, if you're generating the path you can use the same variables in code to append to d -->
  <!ENTITY handFill "0.01">
  <!ENTITY handFill2 "0.02"><!-- Should be 2 * handFill to be centered -->
  <!ENTITY handStroke "0.005"><!-- Should be less than handFill2 to not hide fill -->
]>
<svg height="160" version="1.1" viewBox="-0.6 -0.6 1.2 1.2" width="160" xmlns="http://www.w3.org/2000/svg">
  <g>
    <g>
      <circle class="sensorShape" cx="0" cy="0" fill="#FFF" r="0.4" stroke="black" stroke-width="0.015"/>
      <line stroke="black" stroke-width="0.015" x1="0" x2="0" y1="-0.4" y2="0.4"/>
      <line stroke="black" stroke-width="0.015" x1="-0.4" x2="0.4" y1="0" y2="0"/>
    </g>
    <g class="lsNorthAngleHandsContainer">
      <path d="
        M -&handFill;,0 l0,-0.4
        a &handFill;,&handFill; 0 0,1 &handFill2;,0
        l 0,0.4
        a &handFill;,&handFill; 0 0,1 -&handFill2;,0
      " stroke="red" stroke-linecap="round" stroke-width="&handStroke;" fill="yellow" transform="rotate(348)" />
      <text font-size="0.08" transform="translate(-0.02316467632710395,-0.45125904029352226)">
        348
      </text>
    </g>
  </g>
</svg>
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