Drag And Drop

See the DragDropDemo class.

public void Draw()
{
    using var spaceScope = Style.SpacingYs.Begin(0f);
    for (int i = 0; i < names.Length; i++)
    {
        using var s = Ctx.PushId(i);

        DrawInsertArea(i);

        Gui.Text($"{names[i]}");
        // By placing the InteractiveArea in the same position as Text, 
        // we can make the Text itself interactive.
        Gui.NextRect(Ctx.GetLastWidgetRect()).InteractiveArea();

        // Drag and drop into the InteractiveArea(Text)
        if (Ctx.TryDragDropLast("Key", i))
        {
            if (Gui.BeginAutoSizeSubWindow())
            {
                Gui.FixedWidthText(names[i]);
                Gui.EndAutoSizeSubWindow();
            }
        }

        /// By executing this after <see cref="Context.TryDragDropLast(string, object)"/>,
        /// we enable the item being dragged to be dropped.
        if (Ctx.TryDrop("Key", out var payload))
        {
            var tmp = names[i];
            names[i] = names[(int)payload];
            names[(int)payload] = tmp;

            Logger.Debug($"Dropped:{i},{payload}");
        }
    }
    DrawInsertArea(names.Length);
}

void DrawInsertArea(int insertI)
{
    if (names.Length < insertI)
        throw new ArgumentOutOfRangeException($"{insertI}");

    Gui.NextHeight(20f).Custom<InsertAreaWidget>(true);

    /// Attempt to set the drop target to the rect of <see cref="InsertAreaWidget"/> and perform the insertion.
    /// 
    /// <see cref="Context.TrySetDropTarget(string, Rect)"/> does not return true 
    /// unless an item is currently being dragged.
    if (Ctx.TrySetDropTarget("Key", Ctx.GetLastWidgetRect()) && Ctx.TryDrop("Key", out var payload))
    {
        var insertArrayI = (int)payload < insertI ? insertI - 1 : insertI;
        Logger.Debug($"{payload} was dropped and inserted into {insertArrayI}.");
        names.MoveElement((int)payload, insertArrayI);
    }
}

class InsertAreaWidget : PrimitiveWidget
{
    public override void Build(Shaper shaper)
    {
        shaper.AddInnerFrameRect(Rect, 1f, Color32.Green);
    }
}