[csswg-drafts] [css-display] Understanding blockification (#12216)

chearon has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-display] Understanding blockification ==
I've been struggling to find the value of blockification as a concept. The [base definition](https://www.w3.org/TR/css-display-4/#transformations) is simply:

>  Some layout effects require blockification or inlinification of the box type, which sets the box’s [computed](https://www.w3.org/TR/css-cascade-5/#computed-value) [outer display type](https://www.w3.org/TR/css-display-4/#outer-display-type) to [block](https://www.w3.org/TR/css-display-4/#valdef-display-block) or [inline](https://www.w3.org/TR/css-display-4/#valdef-display-inline) (respectively).

Since outer display type is a box's role _in flow layout_ and blockification happens to _out-of-flow_ boxes (floats, absolutes) or boxes who have a non-flow parent context (grid, flexbox) this seems mostly unnecessary. Is it true that the only important thing blockification does is guarantee a block container is generated and never an inline? That makes some sense, since an IFC is defined to be created by a block container.

Am I missing another important effect?

There seems to be a contradiction with absolute positioning as well. An absolutely positioned element with `left: auto` should be positioned [where it would have been](https://www.w3.org/TR/CSS22/visudet.html#abs-non-replaced-width) in the normal flow. Removing blockification as a concept, the red box below should be to the right of the text, not below it:
    
```html
blockify<span style="position: absolute; width: 5px; height: 5px;"></span>
```

But with blockification, it should go beneath the text, since layout happens after computed styles. Yet all browsers render the box to the right, which also seems more in line with the spirit of the text in CSS 2.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/12216 using your GitHub account


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Received on Tuesday, 20 May 2025 22:46:50 UTC