Containment

Remarks

CSS Containment 2's contain, which is five independent effects behind one property rather than one switch with five settings — and reading it as one switch is how it gets built wrong. The eight Tailwind classes are combinations: contain-content is layout paint style and contain-strict adds size, so a partial implementation makes both aggregates half true rather than absent.

⚠ Size is not "skip the children", and that is the whole trap. § 3.2 says the box is sized as if it had no contents. It still lays them out, paints them, hit-tests them and scrolls them — it only refuses to let them decide its own box. A reading that skipped the subtree would give the same picture in every fixture where the children happen to fit, which is most of them.

⚠ There is no style member, and its absence is a measurement rather than an omission. § 3.4 scopes counters and quotes to the subtree; this engine has neither, so every value of it would compute and move nothing. LayoutStyleBuilder therefore accepts the keyword and maps it to no flag, which is the difference between a property that does nothing here and one that is not understood.

Fields and properties (5)

• None

  The initial value: the contents decide everything they normally would.

• Size

  § 3.2. The box sizes as if it were empty, on both axes.

• InlineSize

  § 3.2's one-axis form. The box sizes as if it were empty across the inline axis only, and its block size still comes from its contents laid out at that width.

• Layout

  § 3.1. An independent formatting context, and a containing block for every out-of-flow descendant.

• Paint

  § 3.3. Descendants are clipped to the box, and it is a containing block and an independent formatting context for the same reasons Layout is.

Used by (5)

• ContainmentReaderVixen.Ui
• ContainmentTestsVixen.Ui.Layout.Tests
• LayoutStyleVixen.Ui.Layout
• LayoutTreeVixen.Ui.Layout
• OverflowReaderVixen.Ui