Syntax highlighting by CodeMirror & WordPress

9 min read

About using of JavaScript library CodeMirror together with CMS WordPress and its integration into WordPress projects (themes and plugins).

CodeMirror is a JavaScript component that provides a code editor in the browser. When a mode is available for the language you are coding in, it will colour your code (syntax highlighting), and optionally help with indentation.

Building a package CodeMirror

At the beginning you need to build a catalogue of CodeMirror with the needed modules, and addons and themes if necessary. This can be done simply. Just download the archive with CodeMirror from the developer website (https://codemirror.net) and removing of unnecessary leave just the needed.

The minimum required package:

Catalogue lib with the files codemirror.js and codemirror.css.
Catalogue mode with needed modes (only js files).
Catalogues theme and addon needs only if use theme or addons.
If you want to publish your project, then you need to use the LICENSE and README.md files.

I give an example of the syntax highlighting of HTML and PHP languages. The needed modes you can specify on this page of the Manual.

And need another two files (config.js, customestyle.css) which I will tell later.

Now all of this must be placed in a directory with the name codemirror at the root of the project. As a result, the builded directory should look something like this:

codemirror-.
           |--lib--.
           |       |--codemirror.js
           |       '--codemirror.css
           |
           |--mode-.
           |       |--xml.js
           |       |--javascript.js
           |       |--css.js
           |       |--htmlmixed.js
           |       |--clike.js
           |       '--php.js
           |
           |--theme-.
           |        '--default.css
           |
           |--addon-.
           |        '--
           |
           |--LICENSE
           |--README.md
           |--config.js
           '--customestyle.css

Loading the scripts of CodeMirror

You must load CodeMirror scripts (those created in previous paragraph) in the header of the page/s. To do this in WordPress there is a special function _enqueue_scripts that load scripts and styles in the header of pages.

Example of loading the scripts with registration:

                                /**
 * Register and enqueue the CodeMirror scripts and styles
 */
function enqueue_codemirror_scripts($hook) {

    if ( 'appearance_page_my-custom-functions' != $hook ) {
        return;
    }

    // Registering scripts
    wp_register_script('codemirror', plugin_dir_url(__FILE__) . 'codemirror/lib/codemirror.js');
    wp_register_script('codemirror_xml', plugin_dir_url(__FILE__) . 'codemirror/mode/xml.js');
    wp_register_script('codemirror_javascript', plugin_dir_url(__FILE__) . 'codemirror/mode/javascript.js');
    wp_register_script('codemirror_css', plugin_dir_url(__FILE__) . 'codemirror/mode/css.js');
    wp_register_script('codemirror_htmlmixed', plugin_dir_url(__FILE__) . 'codemirror/mode/htmlmixed.js');
    wp_register_script('codemirror_clike', plugin_dir_url(__FILE__) . 'codemirror/mode/clike.js');
    wp_register_script('codemirror_php', plugin_dir_url(__FILE__) . 'codemirror/mode/php.js');
    wp_register_script('codemirror_config', plugin_dir_url(__FILE__) . 'codemirror/config.js');
    wp_register_style('codemirror_style', plugin_dir_url(__FILE__) . 'codemirror/lib/codemirror.css');
    wp_register_style('codemirror_customestyle', plugin_dir_url(__FILE__) . 'codemirror/customestyle.css');

    // Enqueue scripts
    wp_enqueue_script('codemirror');
    wp_enqueue_script('codemirror_xml');
    wp_enqueue_script('codemirror_javascript');
    wp_enqueue_script('codemirror_css');
    wp_enqueue_script('codemirror_htmlmixed');
    wp_enqueue_script('codemirror_clike');
    wp_enqueue_script('codemirror_php');
    wp_enqueue_script('codemirror_config');
    wp_enqueue_style('codemirror_style');
    wp_enqueue_style('codemirror_customestyle');

}
add_action( 'admin_enqueue_scripts', 'enqueue_codemirror_scripts' );

                            

And without registration (if there is no need for registration):

                                /**
 * Enqueue the CodeMirror scripts and styles
 */
function enqueue_codemirror_scripts($hook) {
    if ( 'appearance_page_my-custom-functions' != $hook ) {
        return;
    }

    wp_enqueue_script('codemirror', plugin_dir_url(__FILE__) . 'codemirror/lib/codemirror.js');
    wp_enqueue_script('codemirror_xml', plugin_dir_url(__FILE__) . 'codemirror/mode/xml.js');
    wp_enqueue_script('codemirror_javascript', plugin_dir_url(__FILE__) . 'codemirror/mode/javascript.js');
    wp_enqueue_script('codemirror_css', plugin_dir_url(__FILE__) . 'codemirror/mode/css.js');
    wp_enqueue_script('codemirror_htmlmixed', plugin_dir_url(__FILE__) . 'codemirror/mode/htmlmixed.js');
    wp_enqueue_script('codemirror_clike', plugin_dir_url(__FILE__) . 'codemirror/mode/clike.js');
    wp_enqueue_script('codemirror_php', plugin_dir_url(__FILE__) . 'codemirror/mode/php.js');
    wp_enqueue_script('codemirror_php', plugin_dir_url(__FILE__) . 'codemirror/config.js');
    wp_enqueue_style('codemirror_style', plugin_dir_url(__FILE__) . 'codemirror/lib/codemirror.css');
    wp_enqueue_style('codemirror_style', plugin_dir_url(__FILE__) . 'codemirror/customestyle.css');

}
add_action( 'admin_enqueue_scripts', 'enqueue_codemirror_scripts' );

                            

For plugin paths to scripts specified using plugin_dir_url():

                                wp_enqueue_script( 'my_custom_script', plugin_dir_url( __FILE__ ) . 'myscript.js' );

                            

And for themes with the get_template_directory_uri():

                                wp_enqueue_script( 'my_custom_script', get_template_directory_uri( __FILE__ ) . 'myscript.js' );

                            

Note: myscript.is - is the name of the needed file.

Depending on the purpose, you can load scripts on all pages of the website, on all pages of the Admin Area or on a certain page.

Load scripts on all pages of website:

                                function enqueue_codemirror_scripts() {

    // Enqueue scripts
    ...

}
add_action( 'wp_enqueue_scripts', 'enqueue_codemirror_scripts' );

Load scripts on all Admin pages:

                                function enqueue_codemirror_scripts() {

    // Enqueue scripts
    ...

}
add_action( 'admin_enqueue_scripts', 'enqueue_codemirror_scripts' );

Load scripts on a specific Admin page (in my example is edit.php):

                                function enqueue_codemirror_scripts($hook) {
    if ( 'edit.php' != $hook ) {
        return;
    }

    // Enqueue scripts
    ...

}
add_action( 'admin_enqueue_scripts', 'enqueue_codemirror_scripts' );

                            

Note: The page title can be seen in the address bar.

But if you need a page of theme then it will be a little harder.

The name of the page of theme can be identified by the following scheme:

themes.php?page={page}
=>
appearance_page_{page}

If the address of the page you want:

themes.php?page=my-page.php

The title will be appearance_page_my-page.

Settings

All configuration of CodeMirror is made from the config file config.js. You must create this file and put into it the following contents:

                                // Configuration file for CodeMirror v1.0

  var myCodeMirror = CodeMirror.fromTextArea(document.getElementById('CodeMirror'), {
     lineNumbers: true,
     matchBrackets: true,
     mode: 'application/x-httpd-php',
     indentUnit: 4
  });

                            

Note: Use the syntax JavaScript.

The settings are specified as options of variable myCodeMirror.

Option values from my example:

lineNumbers: true,                 // Show line numbers.
matchBrackets: true,               // Highlights paired brace.
mode: "application/x-httpd-php",   // Mode of the highlight.
indentUnit: 4                      // Tab size.

The remaining options can be found on the page of the Manual: https://codemirror.net/doc/manual.html#config

Note: Line with the options, except the last must end with a comma.

Styles

To apply your own styles you need to create the file customestyle.css.

An example of the contents of a file customestyle.css:

                                  .CodeMirror {
     border: 1px solid cornflowerblue;
     height: auto;
  }

                            

Note: Use the syntax CSS.

Processed field

Now the last paragraph. You must specify the CodeMirror area for handling code. This is done using the HTML tag <textarea> (text box) with id - CodeMirror. On needed pages, highlighted code need to wrap in this tag, like so:

                                <textarea cols="50" rows="10" id="CodeMirror" >
</textarea>

Epilogue

If all the code put on one HTML page it will look like this:

                                ...
   <script src="codemirror/lib/codemirror.js"></script>
   <script src="codemirror/mode/xml.js"></script>
   <script src="codemirror/mode/javascript.js"></script>
   <script src="codemirror/mode/css.js"></script>
   <script src="codemirror/mode/htmlmixed.js"></script>
   <script src="codemirror/mode/clike.js"></script>
   <script src="codemirror/mode/php.js"></script>
   <link rel="stylesheet" href="codemirror/lib/codemirror.css">
   <link rel="stylesheet" href="codemirror/theme/default.css">
</head>
<body>
   <div id="container">
      <textarea cols="50" rows="10" id="code" ></textarea>
   </div>
   <script type="text/javascript" language="javascript">
     var myCodeMirror = CodeMirror.fromTextArea(document.getElementById('code'), {
        lineNumbers: true,
        matchBrackets: true,
        mode: 'application/x-httpd-php',
        indentUnit: 4
     });
   </script>
   <style>
     .CodeMirror {
        border: 1px solid cornflowerblue;
        height: auto;
     }
   </style>
</body>
</html>
…

                            