Custom style formats

Currently, there's no admin UI for adding custom styles, yet. Custom styles are CSS classes applied to HTML tags, not to get confused with snippets, which are supposed to be more complex – there's a plugin for snippets.

The quick and dirty approach: adapt the JSON config of your custom profile

Quick example:

{
    "_config_name": "tinymce.profiles.testing",
    "name": "testing",
    "label": "Testing",
    "filter_allowed_html": "a,em,strong,cite,blockquote,ul,ol,li,h3,h4,h5,p,span",
    "tiny_options": {
        "toolbar": "bold italic blockquote | styles | bullist numlist | backdroplink backdropunlink | backdropimage code",
        "plugins": "backdroplink lists autoresize backdropimage",
        "contextmenu": "backdropimage backdroplink",
        "formats": {
            "mycustom": {
                "selector": "p",
                "classes": "my-class"
            },
            "small": {
                "inline": "span",
                "classes": "small"
            },
            "x-large": {
                "inline": "span",
                "classes": "x-large"
            }
        },
        "style_formats": [
            {
                "title": "Paragraph",
                "format": "p"
            },
            {
                "title": "Heading 3",
                "format": "h3"
            },
            {
                "title": "Heading 4",
                "format": "h4"
            },
            {
                "title": "My custom",
                "format": "mycustom"
            },
            {
                "title": "Small text",
                "format": "small"
            },
            {
                "title": "Large text",
                "format": "x-large"
            }
        ]
    }
}

In formats you define your custom block or inline formats and which classes TinyMCE should apply. Classes should be separated by spaces. Also see formats in TinyMCE docs.

In style_formats you define the elements to display in the styles dropdown (see toolbar settings). There you can set the order of elements and define the title to display your custom formats. Also see style_formats in TinyMCE docs.

The actual styles should go to a CSS file (in your theme), and that could get added to the "Content CSS files" admin setting on /admin/config/content/formats/FORMAT.

Example CSS in your theme:

p.my-class {
  font-size: 2rem;
  color: blue;
}
span.small {
  font-size: .7rem;
}
span.x-large {
  font-size: 2rem;
}

The sophisticated approach: hook_tinymce_options_alter()

You need a custom module for that, in our example the module name is "tinycustom". It consists of 3 files: tinycustom.info, tinycustom.module and in a subdirectory css/tinymce-custom.css

Content of tinycustom.info:

type = module
name = TinyMCE Custom
description = Customizes TinyMCE options.
dependencies[] = tinymce
backdrop = 1.x
stylesheets[all][] = css/tinymce-custom.css

Note that the CSS file is attached to all pages via info file.

Content of tinycustom.module:

<?php
/**
 * @file
 * Customizing TinyMCE.
 */

/**
 * Implements hook_tinymce_options_alter().
 */
function tinycustom_tinymce_options_alter(array &$options, $format) {
  if ($format->format == 'filtered_tinymce') {
    // Add CSS file to editor content.
    $module_url = base_path() . backdrop_get_path('module', 'tinycustom');
    $options['tiny_options']['content_css'][] = $module_url . '/css/tinymce-custom.css';

    // Custom content for the styles dropdown. CSS styles for that ship with the
    // css/tinymce-custom.css file from above.
    $options['tiny_options']['style_formats'] = array(
      // Re-use some of the default formats.
      array(
        'title' => 'Paragraph',
        'format' => 'p',
      ),
      array(
        'title' => 'Heading 2',
        'format' => 'h2',
      ),
      array(
        'title' => 'Heading 3',
        'format' => 'h3',
      ),
      // Now our custom items.
      array(
        'title' => 'Large text',
        'inline' => 'span',
        'classes' => 'large-text',
      ),
      array(
        'title' => 'Small text',
        'inline' => 'span',
        'classes' => 'small-text',
      ),
      array(
        'title' => 'Button link',
        'selector' => 'a',
        'classes' => 'specials custom-huge-button',
      ),
    );
  }
}

And finally css/tinymce-custom.css:

.large-text {
  font-size: x-large;
}
.small-text {
  font-size: small;
}
a.specials.custom-huge-button {
  font-weight: bold;
  text-decoration: none;
  color: #fff;
  background: #2a74b5;
  display: inline-block;
  padding: .5em 1em;
  border-radius: 7px;
}

The result looks like this: