godot-docs/tutorials/plugins/running_code_in_the_editor.rst

.. _doc_running_code_in_the_editor:

Running code in the editor
==========================

What is ``@tool``?
------------------

``@tool`` is a powerful line of code that, when added at the top of your script,
makes it execute in the editor. You can also decide which parts of the script
execute in the editor, which in game, and which in both.

You can use it for doing many things, but it is mostly useful in level design
for visually presenting things that are hard to predict ourselves. Here are some
use cases:

- If you have a cannon that shoots cannonballs affected by physics (gravity),
  you can draw the cannonball's trajectory in the editor, making level design a
  lot easier.
- If you have jumppads with varying jump heights, you can draw the maximum jump
  height a player would reach if it jumped on one, also making level design
  easier.
- If your player doesn't use a sprite, but draws itself using code, you can make
  that drawing code execute in the editor to see your player.

.. DANGER::

    ``@tool`` scripts run inside the editor, and let you access the scene tree
    of the currently edited scene. This is a powerful feature which also comes
    with caveats, as the editor does not include protections for potential
    misuse of ``@tool`` scripts.
    Be **extremely** cautious when manipulating the scene tree, especially via
    :ref:`Node.queue_free<class_Node_method_queue_free>`, as it can cause
    crashes if you free a node while the editor runs logic involving it.

How to use it
-------------

To turn a script into a tool, add the ``@tool`` annotation at the top of your code.

To check if you are currently in the editor, use: ``Engine.is_editor_hint()``.

For example, if you want to execute some code only in the editor, use:

.. tabs::
 .. code-tab:: gdscript GDScript

    if Engine.is_editor_hint():
        # Code to execute when in editor.

 .. code-tab:: csharp

    if (Engine.IsEditorHint())
    {
        // Code to execute when in editor.
    }

On the other hand, if you want to execute code only in game, simply negate the
same statement:

.. tabs::
 .. code-tab:: gdscript GDScript

    if not Engine.is_editor_hint():
        # Code to execute when in game.

 .. code-tab:: csharp

    if (!Engine.IsEditorHint())
    {
        // Code to execute when in game.
    }

Pieces of code that do not have either of the 2 conditions above will run both
in-editor and in-game.

Here is how a ``_process()`` function might look for you:

.. tabs::
 .. code-tab:: gdscript GDScript

    func _process(delta):
        if Engine.is_editor_hint():
            # Code to execute in editor.

        if not Engine.is_editor_hint():
            # Code to execute in game.

        # Code to execute both in editor and in game.

 .. code-tab:: csharp

    public override void _Process(double delta)
    {
        if (Engine.IsEditorHint())
        {
            // Code to execute in editor.
        }

        if (!Engine.IsEditorHint())
        {
            // Code to execute in game.
        }

        // Code to execute both in editor and in game.
    }

.. note::

    Modifications in the editor are permanent. For example, in the following
    case, when we remove the script, the node will keep its rotation. Be careful
    to avoid making unwanted modifications.

Try it out
-----------

Add a ``Sprite2D`` node to your scene and set the texture to Godot icon. Attach
and open a script, and change it to this:

.. tabs::
 .. code-tab:: gdscript GDScript

    @tool
    extends Sprite2D

    func _process(delta):
        rotation += PI * delta

 .. code-tab:: csharp

    using Godot;

    [Tool]
    public partial class MySprite : Sprite2D
    {
        public override void _Process(double delta)
        {
            Rotation += Mathf.Pi * (float)delta;
        }
    }

Save the script and return to the editor. You should now see your object rotate.
If you run the game, it will also rotate.

.. image:: img/rotating_in_editor.gif

.. note::

    If you don't see the changes, reload the scene (close it and open it again).

Now let's choose which code runs when. Modify your ``_process()`` function to
look like this:

.. tabs::
 .. code-tab:: gdscript GDScript

    func _process(delta):
        if Engine.is_editor_hint():
            rotation += PI * delta
        else:
            rotation -= PI * delta

 .. code-tab:: csharp

    public override void _Process(double delta)
    {
        if (Engine.IsEditorHint())
        {
            Rotation += Mathf.Pi * (float)delta;
        }
        else
        {
            Rotation -= Mathf.Pi * (float)delta;
        }
    }

Save the script. Now the object will spin clockwise in the editor, but if you
run the game, it will spin counter-clockwise.

Editing variables
-----------------

Add and export a variable speed to the script. To update the speed and also reset the rotation
angle add a setter ``set(new_speed)`` which is executed with the input from the inspector. Modify
``_process()`` to include the rotation speed.

.. tabs::
 .. code-tab:: gdscript GDScript

    @tool
    extends Sprite2D


    @export var speed = 1:
        # Update speed and reset the rotation.
        set(new_speed):
            speed = new_speed
            rotation = 0


    func _process(delta):
    	rotation += PI * delta * speed

 .. code-tab:: csharp

    using Godot;

    [Tool]
    public partial class MySprite : Sprite2D
    {
        private float _speed = 1;

        [Export]
        public float Speed
        {
            get => _speed;
            set
            {
                // Update speed and reset the rotation.
                _speed = value;
                Rotation = 0;
            }
        }

        public override void _Process(double delta)
        {
            Rotation += Mathf.Pi * (float)delta * speed;
        }
    }

.. note::

    Code from other nodes doesn't run in the editor. Your access to other nodes
    is limited. You can access the tree and nodes, and their default properties,
    but you can't access user variables. If you want to do so, other nodes have
    to run in the editor too. Autoload nodes cannot be accessed in the editor at
    all.

Reporting node configuration warnings
-------------------------------------

Godot uses a *node configuration warning* system to warn users about incorrectly
configured nodes. When a node isn't configured correctly, a yellow warning sign
appears next to the node's name in the Scene dock. When you hover or click on
the icon, a warning message pops up. You can use this feature in your scripts to
help you and your team avoid mistakes when setting up scenes.

When using node configuration warnings, when any value that should affect or
remove the warning changes, you need to call
:ref:`update_configuration_warnings<class_Node_method_update_configuration_warnings>` .
By default, the warning only updates when closing and reopening the scene.

.. tabs::
 .. code-tab:: gdscript GDScript

    # Use setters to update the configuration warning automatically.
    @export var title = "":
        set(p_title):
            if p_title != title:
                title = p_title
                update_configuration_warnings()

    @export var description = "":
        set(p_description):
            if p_description != description:
                description = p_description
                update_configuration_warnings()


    func _get_configuration_warnings():
        var warnings = []

        if title == "":
            warnings.append("Please set `title` to a non-empty value.")

        if description.length() >= 100:
            warnings.append("`description` should be less than 100 characters long.")

        # Returning an empty array means "no warning".
        return warnings

Instancing scenes
-----------------

You can instantiate packed scenes normally and add them to the scene currently
opened in the editor. By default, nodes or scenes added with
:ref:`Node.add_child(node) <class_Node_method_add_child>` are **not** visible
in the Scene tree dock and are **not** persisted to disk. If you wish the node
or scene to be visible in the scene tree dock and persisted to disk when saving
the scene, you need to set the child node's :ref:`owner <class_Node_property_owner>`
property to the currently edited scene root.

If you are using ``@tool``:

.. tabs::
 .. code-tab:: gdscript GDScript

    func _ready():
        var node = Node3D.new()
        add_child(node) # Parent could be any node in the scene

        # The line below is required to make the node visible in the Scene tree dock
        # and persist changes made by the tool script to the saved scene file.
        node.set_owner(get_tree().edited_scene_root)

 .. code-tab:: csharp

    public override void _Ready()
    {
        var node = new Node3D();
        AddChild(node); // Parent could be any node in the scene

        // The line below is required to make the node visible in the Scene tree dock
        // and persist changes made by the tool script to the saved scene file.
        node.Owner = GetTree().EditedSceneRoot;
    }

If you are using :ref:`EditorScript<class_EditorScript>`:

.. tabs::
 .. code-tab:: gdscript GDScript

    func _run():
        # `parent` could be any node in the scene.
        var parent = get_scene().get_node("Parent")
        var node = Node3D.new()
        parent.add_child(node)

        # The line below is required to make the node visible in the Scene tree dock
        # and persist changes made by the tool script to the saved scene file.
        node.set_owner(get_scene())

 .. code-tab:: csharp

    public override void _Run()
    {
        // `parent` could be any node in the scene.
        var parent = GetScene().GetNode("Parent");
        var node = new Node3D();
        parent.AddChild(node);

        // The line below is required to make the node visible in the Scene tree dock
        // and persist changes made by the tool script to the saved scene file.
        node.Owner = GetScene();
    }

.. warning::

    Using ``@tool`` improperly can yield many errors. It is advised to first
    write the code how you want it, and only then add the ``@tool`` annotation to
    the top. Also, make sure to separate code that runs in-editor from code that
    runs in-game. This way, you can find bugs more easily.