Incorrect enumeration using CSS counters

Question

Incorrect enumeration using CSS counters

Can you help me figure out why the numbering of sections is incorrect in this CSS code snippet (http://jsfiddle.net/75MHS/)? When I nest h3 and h4 inside div elements, the chapter numbers and section numbers are always off by one. However, if I remove the div containers, the numbering is correct.

<!DOCTYPE html>
<html>
<head>
<style type='text/css'>
h3 {
  counter-increment: chapter;
  counter-reset: section;
}
h3:before {
  content: "Chapter " counter(chapter) " ";
}
h4 {
  counter-increment: section;
}
h4:before {
  content: counter(section) " ";
}
</style>
</head>
<body>
<!-- wrong counter -->
<div><h3>dddd</h3></div>
<div><h4>dddd</h4></div>
<div><h4>dddd</h4></div>
<div><h3>dddd</h3></div>
<div><h4>dddd</h4></div>
<div><h4>dddd</h4></div>

<!-- correct counter -->
<!--
<h3>dddd</h3>
<h4>dddd</h4>
<h4>dddd</h4>
<h3>dddd</h3>
<h4>dddd</h4>
<h4>dddd</h4>
-->
</body>
</html>

html css

Answer 1

Answer №1

The reason why the functionality works properly in the second section (without the use of divs) but not in the first section is due to the scope of the counter. As mentioned by the W3C:

The scope of a counter begins at the initial element in the document that contains a 'counter-reset' for that counter and encompasses the element's descendants and its subsequent siblings along with their descendants.

In the latter part of the HTML, the h3s and h4s are siblings, hence, the counter-reset set on the h3 applies to the subsequent h4 siblings. Whereas, in the first section of the HTML, the h4s are neither descendants nor siblings of the h3s, resulting in the counter-reset not affecting them as they are out of scope.

Another important aspect is that if counter-reset is not defined within a particular scope, it defaults to a value of 0 each time the counter is counter-incremented or referenced in a content rule. This explains why the first part of the HTML displays all 1s:

If 'counter-increment' or 'content' on an element or pseudo-element refers to a counter that is not in the scope of any 'counter-reset', implementations should behave as though a 'counter-reset' had reset the counter to 0 on that element or pseudo-element.

If you need to enclose elements within divs, I would recommend:

Define a counter-reset for the chapters counter on the body, so it doesn't default to 0 each time counter-increment is used.
Either nest the h4s under their parent h3s (although not ideal) or position them as siblings to ensure they fall within the correct scope.

New HTML:

<div>
    <h3>dddd</h3>
    <h4>dddd</h4>
    <h4>dddd</h4>
</div>
<div>
    <h3>dddd</h3>
    <h4>dddd</h4>
    <h4>dddd</h4>
</div>

Addition to CSS:

body {
    counter-reset: chapter;
}

http://jsfiddle.net/myajouri/QpG9d/

Answer 2

The reason why the functionality works properly in the second section (without the use of divs) but not in the first section is due to the scope of the counter. As mentioned by the W3C:

The scope of a counter begins at the initial element in the document that contains a 'counter-reset' for that counter and encompasses the element's descendants and its subsequent siblings along with their descendants.

In the latter part of the HTML, the h3s and h4s are siblings, hence, the counter-reset set on the h3 applies to the subsequent h4 siblings. Whereas, in the first section of the HTML, the h4s are neither descendants nor siblings of the h3s, resulting in the counter-reset not affecting them as they are out of scope.

Another important aspect is that if counter-reset is not defined within a particular scope, it defaults to a value of 0 each time the counter is counter-incremented or referenced in a content rule. This explains why the first part of the HTML displays all 1s:

If 'counter-increment' or 'content' on an element or pseudo-element refers to a counter that is not in the scope of any 'counter-reset', implementations should behave as though a 'counter-reset' had reset the counter to 0 on that element or pseudo-element.

If you need to enclose elements within divs, I would recommend:

Define a counter-reset for the chapters counter on the body, so it doesn't default to 0 each time counter-increment is used.
Either nest the h4s under their parent h3s (although not ideal) or position them as siblings to ensure they fall within the correct scope.

New HTML:

<div>
    <h3>dddd</h3>
    <h4>dddd</h4>
    <h4>dddd</h4>
</div>
<div>
    <h3>dddd</h3>
    <h4>dddd</h4>
    <h4>dddd</h4>
</div>

Addition to CSS:

body {
    counter-reset: chapter;
}

http://jsfiddle.net/myajouri/QpG9d/

Answer 3

Answer №2

Don't overlook the fact that div elements are now included in the DOM tree; you must either address them specifically or delete them altogether.

div {
    counter-increment: chapter;
    counter-reset: section;
}
div:before {
    content: "Chapter " counter(chapter) " ";
}

Answer 4

Don't overlook the fact that div elements are now included in the DOM tree; you must either address them specifically or delete them altogether.

div {
    counter-increment: chapter;
    counter-reset: section;
}
div:before {
    content: "Chapter " counter(chapter) " ";
}

Answer 5

Answer №3

I have applied a new class to the wrapper to distinguish the div elements.

See the Live Demo Here

Here is the HTML code:

<div class="head"><h3>Title Here</h3></div>
<div class="sub"><h4>Subtitle Here</h4></div>
<div class="sub"><h4>Subtitle Here</h4></div>
<div class="head"><h3>Title Here</h3></div>
<div class="sub"><h4>Subtitle Here</h4></div>
<div class="sub"><h4>Subtitle Here</h4></div>

And here is the CSS code:

div.head {
  counter-increment: chapter;
  counter-reset: section;
}

div.head h3:before {
  content: "Chapter " counter(chapter) " ";
}

div.sub {
  counter-increment: section;
}

div.sub h4:before {
  content: counter(section) " ";
}

Answer 6

I have applied a new class to the wrapper to distinguish the div elements.

See the Live Demo Here

Here is the HTML code:

<div class="head"><h3>Title Here</h3></div>
<div class="sub"><h4>Subtitle Here</h4></div>
<div class="sub"><h4>Subtitle Here</h4></div>
<div class="head"><h3>Title Here</h3></div>
<div class="sub"><h4>Subtitle Here</h4></div>
<div class="sub"><h4>Subtitle Here</h4></div>

And here is the CSS code:

div.head {
  counter-increment: chapter;
  counter-reset: section;
}

div.head h3:before {
  content: "Chapter " counter(chapter) " ";
}

div.sub {
  counter-increment: section;
}

div.sub h4:before {
  content: counter(section) " ";
}

Answer 7

Answer №4

The rationale behind this is that counters are "self-nesting," meaning that resetting a counter in a child element or pseudo-element automatically initiates a new instance of the counter." (CSS 2.1, 12.4.1 Nested counters and scope).

Therefore, in the scenario of the "incorrect counter," each div element that contains an h3 element maintains its own counter called chapter, with each h3 incrementing this local counter.

If you wish to group elements using div elements (or section elements), you can structure them like this:

<div class=chapter>
<h3>Title</h3>
<h4>Subheading</h4>
<h4>Subheading</h4>
</div>
<div class=chapter>
<h3>Title</h3>
<h4>Subheading</h4>
<h4>Subheading</h4>
</div>

In this setup, your CSS would target .chapter instead of h3:

.chapter {
  counter-increment: chapter;
  counter-reset: section;
}

Answer 8

The rationale behind this is that counters are "self-nesting," meaning that resetting a counter in a child element or pseudo-element automatically initiates a new instance of the counter." (CSS 2.1, 12.4.1 Nested counters and scope).

Therefore, in the scenario of the "incorrect counter," each div element that contains an h3 element maintains its own counter called chapter, with each h3 incrementing this local counter.

If you wish to group elements using div elements (or section elements), you can structure them like this:

<div class=chapter>
<h3>Title</h3>
<h4>Subheading</h4>
<h4>Subheading</h4>
</div>
<div class=chapter>
<h3>Title</h3>
<h4>Subheading</h4>
<h4>Subheading</h4>
</div>

In this setup, your CSS would target .chapter instead of h3:

.chapter {
  counter-increment: chapter;
  counter-reset: section;
}

Incorrect enumeration using CSS counters

Answer №1

Answer №2

Answer №3

Answer №4

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