How Does CSS Text-Decoration Inheritance Work, and Why Does Overriding it Sometimes Fail?

Understanding text-decoration Inheritance

In CSS, the text-decoration property governs the decorative line styles applied to text. However, unlike other text-related styles such as font-weight, text-decoration behaves distinctly.

The Issue with Overriding Inherited Decoration

Consider the following CSS code:

ul > li {
    text-decoration: none;
}
ul > li.u {
    text-decoration: underline;
}
ul > li > ul > li {
    text-decoration: none;
}
ul > li > ul > li.u {
    text-decoration: underline;
}

This code is intended to prevent inherited decoration from being applied to nested list items. However, the HTML structure below reveals an unexpected result:

<ul>
  <li>Should not be underlined</li>
  <li class="u">Should be underlined
    <ul>
      <li>Should not be underlined</li>
      <li class="u">Should be underlined</li>
    </ul>
  </li>
</ul>

Explanation

The issue lies in the fact that text-decoration applies to all nested elements within the element it is applied to. This means that even if you attempt to override the inherited decoration on nested elements, the inherited decoration will still be applied.

According to the CSS 2.1 specification, "text-decoration on inline boxes are drawn across the entire element, going across any descendant elements without paying any attention to their presence."

Solution

To address this issue, a different approach is required. Instead of relying on nested selectors to override inherited decoration, use an alternate technique such as:

• Using the ::before or ::after pseudo-elements to create decorative lines
• Employing JavaScript to modify the text-decoration property dynamically
• Applying the text-decoration property directly to the desired elements without relying on inheritance

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