When started, an EditorAction temporarily overrides the currently active EditorTool and remains active until either cancelled or completed. The action can complete itself, or rely on user input to resolve. When the action is finished, the previously active EditorTool is re-enabled.
During an EditorAction, press Enter (macOS: Return) to validate the action. To cancel an EditorAction, press Esc.
using UnityEditor;
using UnityEditor.Actions;
using UnityEngine;
// Add a menu item to the Scene View context menu that creates a cube where-ever the mouse clicks.
public class CreateCube : EditorAction
{
GameObject m_GameObject;
int m_UndoStart;
// Prefixing the menu item path with "CONTEXT" indicates that this is a context menu item. Context menu items are
// not added to the application menu bar. The second section of the menu path is the name of the type that this
// menu item is applicable to. The context menu in the Scene View for example will look for context menu items for
// each of the following types:
// 1. The active EditorToolContext type.
// 2. The active EditorTool type.
// 3. All component types in the selection. Ex, Transform, MeshRenderer, BoxCollider, etc...
// As an example, to create a context menu item that is shown when context clicking in the Scene View with a
// GameObject selected that has a MeshFilter component, use "CONTEXT/MeshFilter/My Menu Item".
[MenuItem("CONTEXT/GameObjectToolContext/Create Cube")]
static void Init()
{
EditorAction.Start<CreateCube>();
}
public CreateCube()
{
// Show a preview cube at the cursor.
m_GameObject = GameObject.CreatePrimitive(PrimitiveType.Cube);
// If the action is cancelled, we'll clean up the unused resource by calling Undo.PerformUndo().
Undo.RegisterCreatedObjectUndo(m_GameObject, "Create Cube");
// To avoid an unsightly "jump" when the cursor first moves, disable the preview until we have a valid
// intersection point to place the object.
m_GameObject.SetActive(false);
m_UndoStart = Undo.GetCurrentGroup();
}
public override void OnSceneGUI(SceneView view)
{
var evt = Event.current;
var id = GUIUtility.GetControlID(FocusType.Passive);
if (evt.type == EventType.MouseMove)
{
HandleUtility.AddControl(id, 0);
// Disable preview object so that we don't intersect with object placement ray.
m_GameObject.SetActive(false);
var intersected = HandleUtility.PlaceObject(evt.mousePosition, out var position, out var normal);
m_GameObject.SetActive(true);
if (intersected)
{
Undo.RecordObject(m_GameObject, "Create Cube");
m_GameObject.transform.position = position;
m_GameObject.transform.rotation = Quaternion.LookRotation(normal);
}
}
// By checking that no mouse modifiers are active, we can allow for camera movement without breaking the
// action.
if (evt.type == EventType.MouseDown && evt.modifiers == EventModifiers.None)
{
GUIUtility.hotControl = id;
evt.Use();
}
if (GUIUtility.hotControl == id && evt.type == EventType.MouseUp)
{
evt.Use();
GUIUtility.hotControl = 0;
Finish(EditorActionResult.Success);
}
}
// Since the object we want to instantiate is already in the scene, there is nothing more to do in the OnFinish
// function if the action exits successfully. If the action is cancelled however, we'll remove the instantiated
// object from the scene by calling undo.
protected override void OnFinish(EditorActionResult result)
{
if (result == EditorActionResult.Canceled)
{
Undo.PerformUndo();
return;
}
Selection.activeObject = m_GameObject;
// Merge the selection change and GameObject creation/placement to a single undo entry.
Undo.CollapseUndoOperations(m_UndoStart);
}
}