Unity NonDrawingGraphic to detect raycast in UI without extra draw call

Readme.md

This is a backup to the great anwser that I found on Unity Answers.

@slippdouglas provided a class that enables us to detect raycasts without the extra draw call inside the UI

Source: https://answers.unity.com/questions/1091618/ui-panel-without-image-component-as-raycast-target.html

NonDrawingGraphic.cs

using UnityEngine;
using UnityEngine.UI;

/// A concrete subclass of the Unity UI `Graphic` class that just skips drawing.
/// Useful for providing a raycast target without actually drawing anything.
public class NonDrawingGraphic : Graphic
{
    public override void SetMaterialDirty() { return; }
    public override void SetVerticesDirty() { return; }

    /// Probably not necessary since the chain of calls `Rebuild()`->`UpdateGeometry()`->`DoMeshGeneration()`->`OnPopulateMesh()` won't happen; so here really just as a fail-safe.
    protected override void OnPopulateMesh(VertexHelper vh)
    {
        vh.Clear();
        return;
    }
}

NonDrawingGraphicEditor.cs

using UnityEngine;
using UnityEditor;
using UnityEditor.UI;

//Don't forget to put this file inside a 'Editor' folder
[CanEditMultipleObjects, CustomEditor(typeof(NonDrawingGraphic), false)]
public class NonDrawingGraphicEditor : GraphicEditor
{
    public override void OnInspectorGUI()
    {
        base.serializedObject.Update();
        EditorGUI.BeginDisabledGroup(true);
        EditorGUILayout.PropertyField(base.m_Script, new GUILayoutOption[0]);
        EditorGUI.EndDisabledGroup();
        // skipping AppearanceControlsGUI
        base.RaycastControlsGUI();
        base.serializedObject.ApplyModifiedProperties();
    }
}