A UnityEngine.UI.Graphic subclass that provides only raycast targeting, skipping all drawing.

NonDrawingGraphic.cs

/// @creator: Slipp Douglas Thompson
/// @license: Public Domain per The Unlicense.  See <http://unlicense.org/>.
/// @purpose: A UnityEngine.UI.Graphic subclass that provides only raycast targeting, skipping all drawing.
/// @why: Because this functionality should be built-into Unity.
/// @usage: Add a `NonDrawingGraphic` component to the GameObject you want clickable, but without its own image/graphics.
/// @intended project path: Assets/Plugins/UnityEngine UI Extensions/NonDrawingGraphic.cs
/// @interwebsouce: https://gist.github.com/capnslipp/349c18283f2fea316369

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

/// @creator: Slipp Douglas Thompson
/// @license: Public Domain per The Unlicense.  See <http://unlicense.org/>.
/// @purpose: Slimmed-down Inspector UI for `NonDrawingGraphic` class.
/// @why: Because this functionality should be built-into Unity.
/// @usage: Add a `NonDrawingGraphic` component to the GameObject you want clickable, but without its own image/graphics.
/// @intended project path: Assets/Plugins/Editor/UnityEngine UI Extensions/NonDrawingGraphicEditor.cs
/// @interwebsouce: https://gist.github.com/capnslipp/349c18283f2fea316369

using UnityEngine;
using UnityEditor;
using UnityEditor.UI;



[CanEditMultipleObjects, CustomEditor(typeof(NonDrawingGraphic), false)]
public class NonDrawingGraphicEditor : GraphicEditor
{
	public override void OnInspectorGUI ()
	{
		base.serializedObject.Update();
		EditorGUILayout.PropertyField(base.m_Script, new GUILayoutOption[0]);
		// skipping AppearanceControlsGUI
		base.RaycastControlsGUI();
		base.serializedObject.ApplyModifiedProperties();
	}
}

Ω example-usage.png

perfecto.

Just what I needed, thank you!