SVG & WordPress Custom Fields

The following is a guest post by Ian Marquette. Ian learned that SVG can have a <text> element, meaning that text could come from a dynamic source while still being able to do cool custom SVG-specific stuff to it.

I was recently working on a WordPress-based website that needed an infographic. Being a proponent of responsive design, I drew the infographic in Illustrator and exported it to SVG for scalability. While tinkering around in the backend I discovered that you can add WordPress custom fields to SVG text elements that allow you to control text-based content from within your WordPress CMS. How awesome is that?

Here I’ll explain how I did it, and some further options you might find useful.

Preparing the SVG File

Create the graphic in your vector-editing software of choice. Add placeholder text to the area you’ll want to contain user-controlled text. Here I’ve created a simple graphic for demonstration purposes.

Now open your SVG file with your preferred editor. You’ll have to make some changes to the code. In my example the path had to be changed to a <textpath>, given an ID and linked to using xlink. If I didn’t do this, each individual character in my text would have its own tag, coordinates etc.

<svg width="1000px" height="300px" viewBox="0 0 1000 300"
     xmlns="http://www.w3.org/2000/svg" 
     xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <path id="MyPath"
          d="M 100 200 
             C 200 100 300   0 400 100
             C 500 200 600 300 700 200
             C 800 100 900 100 900 100" />
  </defs>

  <use xlink:href="#MyPath" fill="none" stroke="green"  />

  <text font-family="Helvetica" font-size="42.5">
    <textPath xlink:href="#MyPath">
      SVG Text on a path for WordPress!
    </textPath>
  </text>

</svg>

Here’s a live demo of some text-on-a-path:

See the Pen JoakC by Chris Coyier (@chriscoyier) on CodePen.

You can just copy and paste the markup straight into a WordPress template. You could also use on of the other methods of using SVG on your page, such as linking to the file as an object. Essentially it needs to be inline SVG, not SVG used as an or background-image.

You’ll want to replace the content between the <text> tags with the following code, replacing custom_field with whatever name you want to give yours:

<?php
  global $wp_query;
  $postid = $wp_query->post->ID;
  echo get_post_meta($postid, 'custom_field', true);
  wp_reset_query();
?>

Dropping that within the SVG will look like:

<svg width="1000px" height="300px" viewBox="0 0 1000 300"
     xmlns="http://www.w3.org/2000/svg" 
     xmlns:xlink="http://www.w3.org/1999/xlink">

  <defs>
    <path id="MyPath"
          d="M 100 200 
             C 200 100 300   0 400 100
             C 500 200 600 300 700 200
             C 800 100 900 100 900 100" />
  </defs>

  <use xlink:href="#MyPath" fill="none" stroke="green"  />

  <text font-family="Helvetica" font-size="42.5">
    <textPath xlink:href="#MyPath">
       <?php
        global $wp_query;
        $postid = $wp_query->post->ID;
        echo get_post_meta($postid, 'custom_field', true);
        wp_reset_query();
       ?>
    </textPath>
  </text>

</svg>

Now create a custom field in the WordPress CMS with this label and populate it.

Now if you check out that page, you should see the custom text sitting inside your custom SVG graphic! Of course custom fields are just one way to do this that is rather extensible. You could use do the post title this way, menus, or anything else that dynamically spits out text from any CMS.

Once it’s in there the text can be styled just like regular markup. For instance:

...
<textpath class="text-path" ... >
  ...

.text-path {
  fill: orange;
}

Or any other SVG CSS property. That means using custom fonts via @font-face work just fine. You also have access to nice features such as SVG filters and animation.