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Slots Proposal


These are the new definitions. For all other definitions, consult current spec.

  • slot -- a defined location in a shadow tree. Represented by the slot element.
  • slot name -- the name of a slot.
  • default slot -- a slot for assigning nodes without a slot name.

Slotting Algorithm

The slotting algorithm assigns nodes of a shadow tree host into slots of that tree.

Input HOST -- a shadow tree host Output All child nodes of HOST are slotted

  1. Let TREE be HOST's shadow tree
  2. Let DEFAULT be an empty list of nodes
  3. For each child node NODE of HOST, in tree order:
  4. Let NAME be NODE's slot name
  5. If NAME is missing, add NODE to DEFAULT
  6. Let SLOT be the slot with slot name NAME for TREE
  7. If SLOT does not exist, discard node
  8. Otherwise, assign NODE to SLOT
  9. Let DEFAULT-SLOT be the the default slot for TREE
  10. If DEFAULT-SLOT does not exist, stop
  11. Otherwise, assign all nodes in DEFAULT to DEFAULT-SLOT.

When each node is assigned to a slot, this slot is also added to the node's destination insertion points list.

Get Distributed Nodes Algorithm

The get distributed nodes algorithm recursively collects all nodes that are currently distributed into a given slot

Input SLOT -- a slot in a shadow tree Output LIST - a list of distributed nodes

  1. For each node NODE that is assigned to SLOT:
  2. If NODE is a slot: 1. Let SUB-LIST be the result of (recursively) running the get distributed nodes algorithm with NODE as argument 2. Append all nodes in SUB-LIST to LIST
  3. Otherwise, append NODE to LIST.

Distribution Resolution Algorithm

This algorithm replaces the distribution resolution algorithm from the current spec.

Input NODE-TREE -- a node tree Output The distribution result is updated.

  1. For each shadow host HOST, which participates in NODE-TREE, in tree order:
  2. Run slotting algorithm with HOST as argument
  3. Let SHADOW-TREE be HOST's shadow tree
  4. Run *distribution resolution algorithm (recursively) with SHADOW-TREE as input

slot element

slot element represents a slot in the shadow tree. Has same rendering behavior as the content element.


  • name -- the name of the slot.
interface HTMLSlotElement : HTMLElement {
  attribute DOMString name;
  NodeList getDistributedNodes();
  • name -- reflects the name attribute.
  • getDistributedNodes --- returns result of running the get distributed nodes algorithm.

Extensions to Element

partial interface Element {
  attribute DOMString slot;
  • slot -- reflects the slot attribute. The slot attribute represents the slot name.