ScenePartition/Editor/ScenePartitionSceneViewEditor.cs

using UnityEditor;
using UnityEngine;

namespace VertexColor.ScenePartition.Editor
{
    [InitializeOnLoad]
    public class ScenePartitionSceneViewEditor : UnityEditor.Editor
    {
        private const int cellSize = 10;

        static ScenePartitionSceneViewEditor()
        {
            SceneView.duringSceneGui += HandleDuringSceneGui;
        }

        private static void HandleDuringSceneGui(SceneView sceneView)
        {
            if (Event.current.modifiers != EventModifiers.Control) return;

            Vector3 gridPosition = CalculateGridPosition(Event.current.mousePosition);
            int gridId = SceneGrid.CalculateGridPosition(gridPosition, 10);

            int x = Mathf.FloorToInt(gridPosition.x / cellSize);
            int z = Mathf.FloorToInt(gridPosition.z / cellSize);

            Vector3 cellOrign = new Vector3(x * cellSize, 0, z * cellSize);
            Vector3[] lines = new Vector3[] {
            new Vector3(0, 0, 0) + cellOrign, new Vector3(0, 0, cellSize) + cellOrign,                  // Left Bottom -> Left Top
            new Vector3(cellSize, 0, 0) + cellOrign, new Vector3(cellSize, 0, cellSize) + cellOrign,    // Right Bottom -> Right Top
            new Vector3(0, 0, 0) + cellOrign, new Vector3(cellSize, 0, 0) + cellOrign,                  // Left Bottom -> Right Bottom
            new Vector3(0, 0, cellSize) + cellOrign, new Vector3(cellSize, 0, cellSize) + cellOrign,    // Left Top -> Right Top
        };

            Handles.DrawDottedLines(lines, 10.0f);
            Handles.Label(cellOrign + new Vector3(cellSize * 0.5f, 0, cellSize * 0.5f), new GUIContent($"{gridId}"));

            if (Event.current.button == 1 && Event.current.type == EventType.MouseDown)
            {
                GenericMenu menu = new GenericMenu();

                menu.AddItem(new GUIContent($"Load {gridId}"), false, Load, gridId);
                menu.ShowAsContext();

                Event.current.Use();
            }

            SceneView.RepaintAll();
        }

        private static Vector3 CalculateGridPosition(Vector2 mousePosition)
        {
            if (Event.current == null) return Vector3.zero;

            Ray ray = HandleUtility.GUIPointToWorldRay(mousePosition);
            Plane plane = new Plane(Vector3.up, Vector3.zero); // Horizontal plane at y = 0

            if (!plane.Raycast(ray, out float distance)) return Vector3.zero;

            Vector3 intersectionPoint = ray.GetPoint(distance);
            return intersectionPoint;
        }

        private static void Load(object gridId)
        {
            if (gridId == null) return;
            if (gridId is not int gridPos) return;


        }
    }
}