Rectangle into which the selected creative render is fitted and clipped without changing its manifest or renderer.
How the creative render is scaled into the slot. contain preserves the whole render, cover fills and crops, and stretch fills without preserving aspect ratio.
Slot overflow is always clipped so composition is deterministic.
Optionaldecorations
Declarative, non-executable placement frame. Consumers create the canvas, paint behind_creative decorations in array order, fit and clip the selected creative render into creative_slot, then paint in_front_of_creative decorations in array order. Text is plain text and image assets are immutable, digest-pinned resources; scripts, HTML, CSS, event handlers, and arbitrary style properties are forbidden.