Reordering

Lets the user reorder the items: each gets a handle to drag, which also opens a menu (Move up, Move down, Move to top, Move to bottom) for moving without dragging; with DragWholeItem and an ItemMenu, the moves go in each item's ⋯ menu instead, and the item drags from anywhere. Needs an ItemKey and every item shown: no paging and no ItemsProvider. On interactive pages bind the order with @bind-Items; on static pages give it a Name inside a form and pass the posted ListOrder back as Order.

For a Reorderable list on a static page, the prefix of the fields it posts: {Name}.Keys and {Name}.Move, bound as a ListOrder. Without it, a static page shows no handles.

For a Reorderable list on a static page, what the form posted: the list shows the posted order with the move applied, and focuses the moved item's handle (or ⋯ button).

For a Reorderable list on a static page with script, posts the form after each move, for pages that save every move. Otherwise moves stay in the page until the form is submitted. With JavaScript off, each move from an item's menu posts anyway.

For a Reorderable list, lets a drag start anywhere on an item, not only on its handle: with a mouse after a small move, on touch after a long press (so a swipe still scrolls the page). Links, buttons and fields in the item keep their presses; the item's own link (ItemHref) or button (OnItemClick) still works on a click. With an ItemMenu there are no handles: each item's ⋯ menu ends with a Move submenu (Move up, Move down, Move to top, Move to bottom); without one, the handle stays as the menu of moves.

Makes the list a zone of the DropZoneGroup<T> around it: it shows the group's items whose zone is this one, and items move here from the group's other zones. Name each zone with AriaLabel, which also names it in the menu of moves.

For a Zone, which items may move here from other zones, such as t => t.Reviewed.

For a Zone, how many items it holds at most; a full zone takes no more from the others.

Runs before a move changes the list, on interactive pages: save it here, or set Cancel to keep the item where it was. A dragged item stays where it was dropped while this runs, for up to 3 seconds; moves made meanwhile are ignored.