gaemstone/src/gaemstone.Client/Systems/ImGuiManager.cs

using System;
using gaemstone.ECS;
using gaemstone.Flecs;
using ImGuiNET;
using Silk.NET.Input;
using Silk.NET.OpenGL.Extensions.ImGui;
using static gaemstone.Client.Components.InputComponents;
using static gaemstone.Client.Systems.Windowing;

namespace gaemstone.Client.Systems;

[Module]
[DependsOn<gaemstone.Client.Components.InputComponents>]
[DependsOn<gaemstone.Client.Systems.InputManager>]
[DependsOn<gaemstone.Client.Systems.Windowing>]
public class ImGuiManager
{
	[Entity, Add<Pipeline.Phase>]
	[DependsOn<SystemPhase.OnLoad>]
	public struct ImGuiUpdatePhase {  }

	[Entity, Add<Pipeline.Phase>]
	[DependsOn<SystemPhase.OnStore>]
	public struct ImGuiRenderPhase {  }

	[Component, Singleton]
	public class ImGuiData
	{
		public ImGuiController Controller { get; }
		internal ImGuiData(ImGuiController controller) => Controller = controller;
	}

	[System<SystemPhase.OnLoad>]
	public unsafe void Initialize(Universe universe, GameWindow window, Canvas canvas,
			[Source<Input>] IInputContext inputContext, [Not] ImGuiData _)
		=> universe.LookupOrThrow<ImGuiData>().Set(new ImGuiData(
			new(canvas.GL, window.Handle, inputContext, () => {
				var IO = ImGui.GetIO();

				// Do not save a settings or log file.
				IO.NativePtr->IniFilename = null;
				IO.NativePtr->LogFilename = null;

				IO.BackendFlags |= ImGuiBackendFlags.HasMouseCursors
				                |  ImGuiBackendFlags.HasSetMousePos;
				IO.ConfigFlags  |= ImGuiConfigFlags.NavEnableKeyboard
				                |  ImGuiConfigFlags.NavEnableSetMousePos;
				IO.ConfigWindowsResizeFromEdges = true;

				// Set up key mappings.
				foreach (var imguiKey in Enum.GetValues<ImGuiKey>()) {
					var name = imguiKey.ToString();

					// Adjust ImGuiKey enum names to match Silk.NET.Input.Key enum.
					if (name.StartsWith("_")) name = name.Replace("_", "Number");
					if (name.EndsWith("Arrow")) name = name[..^"Arrow".Length];
					if (name.EndsWith("Ctrl" )) name = name.Replace("Ctrl", "Control");

					if (!name.EndsWith("Bracket")) { // Leave "LeftBracket" and "RightBracket" alone.
						if (name.StartsWith("Left" )) name = name["Left" .Length..] + "Left";
						if (name.StartsWith("Right")) name = name["Right".Length..] + "Right";
					}

					if (Enum.TryParse<Key>(name, true, out var silkKey))
						IO.KeyMap[(int)imguiKey] = (int)silkKey;
				}
			})));

	[System<SystemPhase.OnLoad>]
	public static void UpdateMouse(Universe universe,
		[Source<Mouse>] IMouse impl, ImGuiData _)
	{
		var input  = universe.LookupOrThrow<Input>();
		var module = universe.LookupOrThrow<ImGuiManager>();
		var capturedBy = input.GetTarget<MouseInputCapturedBy>();
		var isCaptured = (capturedBy != null);
		// If another system has the mouse captured, don't do anything here.
		if (isCaptured && (capturedBy != module)) return;

		var IO = ImGui.GetIO();

		// Set the mouse position if ImGui wants to move it.
		if (IO.WantSetMousePos) impl.Position = IO.MousePos;

		// Capture the mouse input it is above GUI elements.
		if (IO.WantCaptureMouse != isCaptured) {
			if (IO.WantCaptureMouse) input.Add   <MouseInputCapturedBy>(module);
			else                     input.Remove<MouseInputCapturedBy>(module);
		}

		var cursor = ImGui.GetMouseCursor();
		impl.Cursor.CursorMode = (cursor == ImGuiMouseCursor.None)
			? CursorMode.Hidden : CursorMode.Normal;
		// TODO: Use additional cursors once Silk.NET supports GLFW 3.4.
		impl.Cursor.StandardCursor = cursor switch {
			ImGuiMouseCursor.Arrow      => StandardCursor.Arrow,
			ImGuiMouseCursor.TextInput  => StandardCursor.IBeam,
			// ImGuiMouseCursor.ResizeAll  => StandardCursor.,
			ImGuiMouseCursor.ResizeNS   => StandardCursor.VResize,
			ImGuiMouseCursor.ResizeEW   => StandardCursor.HResize,
			// ImGuiMouseCursor.ResizeNESW => StandardCursor.,
			// ImGuiMouseCursor.ResizeNWSE => StandardCursor.,
			ImGuiMouseCursor.Hand       => StandardCursor.Hand,
			// ImGuiMouseCursor.NotAllowed => StandardCursor.,
			_ => StandardCursor.Default,
		};
	}

	[System<ImGuiUpdatePhase>]
	public static void Update(TimeSpan delta, ImGuiData imgui)
		=> imgui.Controller.Update((float)delta.TotalSeconds);

	[System]
	public static void ShowDemoWindow(ImGuiData _)
		=> ImGui.ShowDemoWindow();

	[System<ImGuiRenderPhase>]
	public static void Render(ImGuiData imgui)
		=> imgui.Controller.Render();
}