Tree

See the TreeDemo.cs.

using Gridrand.RimGui.Manual;
using Gridrand.RimGui.Manual.Utility;
using System.Collections.Generic;

namespace Gridrand.RimGui.Extensions.Manual
{
    /// <summary>
    /// Demonstrates how to implement and display tree structures with different scrolling behaviors.
    /// </summary>
    class TreeDemo : ManualBase, IManual
    {
        readonly Tree dynamicScrollTree;
        readonly Tree fixedScrollTree;

        public TreeDemo(ManualBaseResource p) : base(p)
        {
            dynamicScrollTree = new();
            fixedScrollTree = new();
        }

        public void Draw()
        {
            Gui.ToolTip("By holding down the Alt key while clicking triangle icon, you can open / close all child elements.");

            DrawWithDynamicScroll(dynamicScrollTree);
            DrawWithFixedScroll(fixedScrollTree);
        }

        void DrawWithDynamicScroll(Tree tree)
        {
            Gui.Heading("Scroll");

            using var entries = tree.ExpansionControl.CollectExpandedNodes(tree.Roots);

            // Render a scrollable tree.
            if (Gui.NextHeight(200f).BeginScroll())
            {
                // Set SpacingY to 0 within this scope.
                using var s = Style.SpacingYs.Begin(0f);

                for (int i = 0; i < entries.Length; i++)
                {
                    DrawNode(tree, entries[i]);
                }
                Gui.EndScroll();
            }
        }

        void DrawWithFixedScroll(Tree tree)
        {
            Gui.HeadingTooltip(
                "FixedScrollTree",
                "It only processes the displayed nodes, making it fast even when there are many.");

            using var entries = tree.ExpansionControl.CollectExpandedNodes(fixedScrollTree.Roots);

            // Set SpacingY to 0 within this scope.
            using (Style.SpacingYs.Begin(0f))
            // Render a fixed-size scrollable tree.
            using (Gui.NextHeight(200f).BeginFixedScroll(entries.Length))
            {
                var scrollRect = Ctx.GetWidgetRect();

                while (Ctx.AdvanceFixedScrollItem())
                {
                    var entry = entries[Ctx.GetFixedScrollIndex()];
                    DrawNode(tree, entry);
                }

                // Try deselect all
                Gui.NextRect(scrollRect).DeselectionArea(fixedScrollTree.Selection);
            }
        }

        void DrawNode(Tree tree, TreeNodeEntry<Node> entry)
        {
            using var s = Ctx.PushId(entry.Node.GetHashCode());
            var nodeRect = Ctx.AllocateRect();

            var (FoldoutRect, MainRect) = LayoutBuilder.BuildFoldoutNode(nodeRect, entry.Level);

            // To process input first and then draw later
            using (Ctx.BeginDeferredBuilding())
            {
                if (entry.Node.HasChild)
                {
                    Gui.NextRect(FoldoutRect).TreeFoldout(tree.ExpansionControl, entry.Node);
                }

                // note:Unscaled because the scale has already been taken into account.
                using var rects2 = Ctx.LayoutBuilder.FixedUnscaled(MainRect.height).Fit(1).BuildHorizontal(MainRect);
                var isCheck = entry.Node.IsChecked;
                Gui.NextRect(rects2.R0).CheckBox(ref isCheck);
                Gui.NextRect(rects2.R1).Text(entry.Node.Name);
                entry.Node.IsChecked = isCheck;
            }

            // When clicked, it will update the tree's selection state with this node.
            Gui.NextRect(nodeRect).SelectableItem(tree.Selection, entry.Node);
        }

        /// <summary>
        /// Represents a node in the tree structure.
        /// </summary>
        class Node
        {
            public bool IsChecked { get; set; }
            public string Name { get; set; }
            public List<Node> Children { get; private set; } = new();
            public bool HasChild => 0 < Children.Count;

            public Node AddChildren(params Node[] children)
            {
                Children.AddRange(children);
                return this;
            }
        }

        class Tree
        {
            // Fixed-size scrollable tree structure data.
            public List<Node> Roots { get; } = new();
            public ItemSelection<Node> Selection { get; } = new();
            public TreeExpansionControl<Node> ExpansionControl { get; }

            public Tree()
            {
                ExpansionControl = new TreeExpansionControl<Node>(n => n.Children);

                BuildTree(Roots, Selection);

                foreach (var n in Roots)
                    ExpansionControl.SetExpandedRecursively(n, true);
            }

            static void BuildTree(List<Node> roots, ItemSelection<Node> selection)
            {
                var n = 0;

                roots.Add(new Node() { Name = ProcessName(ref n) }
                .AddChildren(
                    new Node() { Name = ProcessName(ref n) }
                    .AddChildren(
                        new Node() { Name = ProcessName(ref n) },
                        new Node() { Name = ProcessName(ref n) }),
                    new Node() { Name = ProcessName(ref n) }
                    .AddChildren(new Node() { Name = ProcessName(ref n) })));


                roots.Add(new Node() { Name = ProcessName(ref n) }
                .AddChildren(
                    new Node() { Name = ProcessName(ref n) }
                    .AddChildren(
                        new Node() { Name = ProcessName(ref n) })));

                roots.Add(new Node() { Name = ProcessName(ref n) });
                roots.Add(new Node() { Name = ProcessName(ref n) });
                roots.Add(new Node() { Name = ProcessName(ref n) });
                roots.Add(new Node() { Name = ProcessName(ref n) });

                selection.Select(roots[0]);
                selection.Select(roots[1]);

            }
            static string ProcessName(ref int number)
            {
                var result = number;
                number++;
                return result.ToString();
            }
        }
    }
}