Drag And Drop

See the DragAndDropDemo.cs.

using Gridrand.Contracts;
using System;
namespace Gridrand.RimGui.Manual
{
    /// <summary>
    /// Drag and drop demo.
    /// </summary>
    class DragDropDemo : ManualBase, IManual
    {
        string[] names = new string[3] { "A", "B", "C", };

        public DragDropDemo(ManualBaseResource p) : base(p)
        {
        }

        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("DragInfo"))
                    {
                        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);
            }
        }
    }
}