Module drag 

Reusable drag-to-reorder interaction model — the single source of truth for live-reflow list reordering (weather’s saved cities today; notes, playlists, contacts next).

Like Scrollbar, this is a pure state machine, not a widget: it turns (list geometry, cursor) into the live insertion index, per-item reflow shift, and floating ghost rect. DragController::cancel just forgets the session, so cancel is a no-op by construction. A generic Id payload lets a caller key selection/presence to the moving item without the controller understanding it.

The reflow math assumes a uniform list (one extent + fixed gap per item) — true of every current adopter. A non-uniform list can still drive the insertion index via its own ListMetrics, but the whole-slot reflow shift only makes sense for uniform slots.

Structs

DragController

A single-axis drag-to-reorder controller. Construct one per reorderable list (DragController::vertical / DragController::horizontal) and drive it from the owner’s event handler:

ListMetrics

Uniform geometry of a reorderable list along the drag axis, in the same (logical, scroll-adjusted) coordinate space as the cursor.

Enums

Axis

Which way a reorderable list runs. The controller pins the cross axis while dragging so the ghost slides only along the list.

Constants

REORDER_THRESHOLD_PX

Pixels of pointer travel before a press is promoted to a reorder drag, so a plain click never jitters into a move.