Range select

Selecting forty rows one click at a time is the kind of work interfaces are supposed to absorb. Range select absorbs it with two clicks: the first sets an anchor, the second says how far, and everything between the two ends up selected. It came out of desktop file managers, arrived on the web with Gmail in 2004, and is now expected in every list of things: mail, files, tracks, layers, spreadsheet cells, and any table with a checkbox column.

The anchor is the part implementations get wrong. A range is defined by two ends, so the list has to remember which item was the last plain click and keep it while shifted clicks move only the other end. Shift clicking again from the same anchor should redraw the range rather than add a second one, so shrinking a range is just clicking nearer the anchor. The anchor moves only on an unmodified click, or on the first item of a modifier key pick, and it survives scrolling and sorting. Get that wrong and the reader experiences it as a list that forgets where they started.

Order is the other trap. The range is defined over the list as currently rendered, not over the underlying data, so a sort or a filter applied while a range is selected leaves a selection that is no longer contiguous. Most applications keep the items and drop the claim of contiguity, which is honest. Collapsed groups raise the same question in reverse: a range that spans a collapsed section usually should include the rows hidden inside it, and should say so, because a count that jumps from nine to thirty on expand reads as a bug.

Keyboard and screen reader users need the same reach, and the APG spells it out: Shift + Down extends the selection by one, Shift + Home and Shift + End extend to the ends, and Control + A selects everything. The visible state has to be aria-selected on each item, with the header checkbox reporting aria-checked="mixed" when only some rows are in, since a half selected list is a real third state rather than an unchecked one. Touch has no Shift at all, which is why phones answer with a selection mode: one long press enters it, and taps extend from there.