Where a new surface visually originates signals which control owns it

What it is

A menu that slides in from the left edge reads as a system panel; the same menu expanding from a gear icon reads as that button’s accessory. Where a new surface grows from geometrically is who people file it under. That is origin location as a belonging index. The object is usually a newly appeared surface; it does not need to share pixel identity with the host control.

Why it happens

Spatial attention uses “where from” to fill in “belongs to.” The expansion origin is a momentary pointer: the new layer’s parent is the control at that coordinate. If the origin is a screen edge or dead centre, the parent is filed as “the environment” or “the system,” not a specific control. Collapsing back through the same point reconfirms belonging; collapsing somewhere else rewrites belonging on the way out.

This is not a shared-element weld. A shared element needs a continuous surface of one object at both ends. Origin location only needs a path from host to new surface; the surface can be an entirely new menu, sheet or bubble. Without the path, host and surface are often far apart in the static layout, proximity cannot help, and belonging falls back to memory.

Studying it

For one host–surface pair, manipulate the expansion anchor: host centre, screen edge, viewport centre. Measure later identification of “who opened this,” whether dismiss taps still hit the host, and whether belonging follows if the surface is dragged elsewhere. Independent variables: anchor location, whether collapse returns to the anchor. Dependent variables: host identification, distribution of dismiss taps.

A row of similar hosts is the stress test: a few pixels of anchor error bind the surface to a neighbour.

Where it stops holding

• If the host has scrolled off-screen, the anchor sits on empty list and belonging points at an absent parent; an edge entrance plus copy that names the source is cleaner.
• A full-screen alert belongs to no control; exploding it out of a small icon forges a host.
• Origin location cannot carry a whole product map by itself; it only binds this pair of surfaces.

Applying it

• Menus, bubbles and lightweight panels opened from a control should expand from and collapse into that control’s anchor.
• System-level surfaces that have nothing to do with the current control should not borrow a control anchor.
• Check: hide the transition and ask who opened it. Pointing at the wrong control, or “I don’t know,” means the anchor did not index belonging.

Related

• Same group: F7.07.2 A consistent spatial model reduces navigation confusion · F7.07.3 The spatial model must hold across the product
• Nearby: F7.01.2 Motion shows where an element came from and belongs · F7.04.1 A shared element keeps the object's identity continuous · F1.08 Overlay anchoring
• Search terms: origin location · spatial belonging · anchor point