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csssvgfirefoxcss-variables

Why doesn't Firefox show my SVG icons, and how to do it?

Context
I am creating a static website using HTML, CSS and JS only (for learning purposes). I successfully implemented two themes. In order to change it, I added an SVG icon in a button element. The svg then changes according to the theme (moon or sun).

Problem
While everything runs well in a chromium browser, the SVGs don't show at all using Firefox, but the buttons work as expected. I suspect this comes from the way I use CSS variables to change the path of the SVG on hover. However, using variables is quite the goal in my case.

Outputs
Here is the (expected) result I get in the chromium based browser:

Chromium-based

Here is the one I get in Firefox:

enter image description here

Question
How can I make the SVGs appear in Firefox using CSS variables ?

MWE
Here is an example. As you can see, in Firefox and unless the path is set inline as in the third svg icon, there is just nothing showing.

:root {
  --square: "M 0 0 H 50 V 50 H 0 Z";
  --triangle: "M 0 0 V 50 H 50 Z";
  --color1: red;
  --color2: green;
  --color3: blue;
}


/*Doesn't work in FF*/
#path1 {
  d: path(var(--square));
}


/*Doesn't work in FF either*/
#path2 {
  d: path("M 25 0 L 50 25 L 25 50 L 0 25 Z");
}


/*Behaviour when hovered*/
#btn1:hover path {
  d: path(var(--triangle));
  fill: var(--color1);
}

#btn2:hover path {
  d: path(var(--triangle));
  fill: var(--color2);
}

#btn3:hover path {
  d: path(var(--triangle));
  fill: var(--color3);
}


/*Some more (off-topic) styling*/

button:hover {
  cursor: pointer;
}

svg {
  width: 25;
  height: 25;
  max-width: 50px;
  max-height: 50px;
}
<button id="btn1">
  <svg>
    <path id="path1" />
  </svg>
</button>

<button id="btn2">
  <svg>
    <path id="path2" />
  </svg>
</button>

<button id="btn3">
  <svg>
    <path id="path3" d="M 0 0 H 50 V 50 Z";/>
  </svg>
</button>

Solution

  • Because d is an attribute, not a CSS property. It is working in chromium browsers, as an experimental implementation. But it was discussed and then rejected.

    https://github.com/w3c/svgwg/issues/49

    https://github.com/w3c/svgwg/issues/119

    "How can I make the SVGs appear in Firefox using CSS variable" ?

    Assign the whole SVG as a CSS variable and put it as a "background" or "background-image". You can save the whole SVG by encoding in base64 (bad practice) or use an URL encoder for SVG like this one.

    .bg {
  background: url(var(--yourCSSVar)); // or background-image even better
}

    How to that:

    SVG code (original):

    <svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
     viewBox="0 0 10 10" style="enable-background:new 0 0 10 10;" xml:space="preserve">
<style type="text/css">
    .st0{fill:#FF00FF;}
</style>
<g>
    <rect x="3" y="3" class="st0" width="4" height="4"/>
    <path d="M6.5,3.5v3h-3v-3H6.5 M7.5,2.5h-5v5h5V2.5L7.5,2.5z"/>
</g>
</svg>

    Copy your SVG code and google for a URL encoder for SVGs or a base64 encoder (an example of URL encoder, an example of base64 encoder). Copy the output and you should have a string that looks like this one:

        "data:image/svg+xml,%3Csvg version='1.1' xmlns='http://www.w3.org/2000/svg'
xmlns:xlink='http://www.w3.org/1999/xlink' x='0px' y='0px' viewBox='0 0 10 10' style='enable-background:new 0 0 10 10;'
xml:space='preserve'%3E%3Cstyle type='text/css'%3E .st0%7Bfill:%23FF00FF;%7D%0A%3C/style%3E%3Cg%3E%3Crect x='3' y='3'
class='st0' width='4' height='4'/%3E%3Cpath d='M6.5,3.5v3h-3v-3H6.5
M7.5,2.5h-5v5h5V2.5L7.5,2.5z'/%3E%3C/g%3E%3C/svg%3E%0A"

    Now, I will create a code snippet and use that string.

    :root {
--encodedSVG: url("data:image/svg+xml,%3Csvg version='1.1' id='Layer_1' xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink' x='0px' y='0px' viewBox='0 0 10 10' style='enable-background:new 0 0 10 10;' xml:space='preserve'%3E%3Cstyle type='text/css'%3E .st0%7Bfill:%23FF00FF;%7D%0A%3C/style%3E%3Cg%3E%3Crect x='3' y='3' class='st0' width='4' height='4'/%3E%3Cpath d='M6.5,3.5v3h-3v-3H6.5 M7.5,2.5h-5v5h5V2.5L7.5,2.5z'/%3E%3C/g%3E%3C/svg%3E%0A");
--svgOnHover: url("data:image/svg+xml,%3Csvg version='1.1' id='Layer_1' xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink' x='0px' y='0px' viewBox='0 0 10 10' style='enable-background:new 0 0 10 10;' xml:space='preserve'%3E%3Cstyle type='text/css'%3E .st0%7Bfill:%23FF00FF;%7D%0A%3C/style%3E%3Cg%3E%3Cpolygon class='st0' points='3.95,6.08 1.54,5.71 3.28,3.92 2.88,1.44 5,2.61 7.12,1.44 6.72,3.92 8.46,5.71 6.05,6.08 5,8.32 '/%3E%3Cpath d='M6.46,2.37L6.26,3.6l-0.08,0.5l0.35,0.36l0.89,0.91L6.24,5.55L5.71,5.63L5.49,6.11L5,7.15L4.51,6.11L4.29,5.63L3.76,5.55 L2.57,5.37l0.89-0.91l0.35-0.36L3.74,3.6l-0.2-1.22l0.98,0.54L5,3.18l0.48-0.27L6.46,2.37 M7.78,0.5L5,2.04L2.22,0.5l0.53,3.26 L0.5,6.06l3.11,0.48L5,9.5l1.39-2.96L9.5,6.06L7.25,3.76L7.78,0.5L7.78,0.5z'/%3E%3C/g%3E%3C/svg%3E%0A");
}


h1 {
  text-align: center;
}

.svg-background {
  height: 100%;
  min-height: 200px;
  width: 30%;
  margin: 0 auto;
  outline: 2px solid;
  background-image: var(--encodedSVG);
  background-repeat: no-repeat;
}


.svg-background:hover {
  background-image: var(--svgOnHover);
}
    <h1> Example </h1>
<div class="svg-background"></div>