Function apply_click

fn apply_click(
    state: &mut LibraryState,
    rows: &[(Pick, Rect)],
    pick: &Pick,
    ctrl: bool,
    shift: bool,
)

One click on a row/tile, resolved against the rows as they were drawn this frame. Plain replaces the selection, Ctrl toggles one item, Shift takes the range from the anchor (which stays put, so a second Shift+click re-ranges from the same place, like every file explorer).