Improve Inspector plugin tutorial with a better example

tutorials/plugins/editor/inspector_plugins.rst

@@ -4,53 +4,79 @@ Inspector plugins
 =================
 
 The inspector dock supports custom plugins to create your own widgets for
-editing properties. This tutorial explains how to use the
-:ref:`class_EditorInspectorPlugin` and :ref:`class_EditorProperty` classes to
-write such plugins with the example of creating a custom value editor.
+editing properties. This can be beneficial when working with custom datatypes
+and resources, but may be used to change the default behavior for built-in
+types as well. It is possible to introduce custom controls for specific properties,
+entire objects, and even detached controls associated with particular datatypes.
+
+This tutorial explains how to use the :ref:`class_EditorInspectorPlugin` 
+and :ref:`class_EditorProperty` classes to create a custom control for each
+property of the integer type, replacing the default behavior with a button 
+that generates random values between numbers 0 and 99.
+
+.. figure:: img/inspector_plugin_example.png
+   :align: center
+
+   The default behavior on the left, and the end result on the right.
+
 
 Setup
 -----
 
-Just like :ref:`doc_making_plugins`, we start out by making a new plugin,
-getting a ``plugin.cfg`` file created, and start with our
-:ref:`class_EditorPlugin`.  However, instead of using
-``add_custom_node`` or ``add_control_to_dock`` we'll use
-``add_inspector_plugin``.
+Follow the :ref:`doc_making_plugins` guide to setup the framework for your 
+new plugin. Lets assume you've called your plugin folder ``my_inspector_plugin``.
+If so, you should end up with a new ``addons/my_inspector_plugin`` folder 
+that contains two files: ``plugin.cfg`` and ``plugin.gd``.
+
+As before, ``plugin.gd`` is a script extending :ref:`class_EditorPlugin` and you
+need to introduce new code for its ``_enter_tree`` and ``_exit_tree`` methods. To
+setup your inspector plugin you must load its script and then create and add
+the instance using ``add_inspector_plugin``. If the plugin is disabled you should 
+remove the instance you have added using ``remove_inspector_plugin``.
+
+.. note:: Take note, that here you are loading a script and not a packed scene.
+          Therefore you should use ``new()`` instead of ``instance()``.
 
 .. tabs::
   .. code-tab:: gdscript GDScript
-    # MyEditorPlugin.gd
+    # plugin.gd
     tool
     extends EditorPlugin
 
-
     var plugin
 
 
     func _enter_tree():
-        # EditorInspectorPlugin is a resource, so we use `new()` instead of `instance()`.
-        plugin = preload("res://addons/MyPlugin/MyInspectorPlugin.gd").new()
+        plugin = preload("res://addons/my_inspector_plugin/MyInspectorPlugin.gd").new()
         add_inspector_plugin(plugin)
 
 
     func _exit_tree():
         remove_inspector_plugin(plugin)
 
+
 EditorInspectorPlugin
 ---------------------
 
-To actually connect into the Inspector, we create a
-:ref:`class_EditorInspectorPlugin` class. This script provides the "hooks" to
-the inspector. Thanks to this class, the editor will call the functions within
-the EditorInspectorPlugin while it goes through the process of building the UI
-for the inspector. The script is used to check if we should enable ourselves for
-any :ref:`class_Object` that is currently in the inspector (including any
-:ref:`class_Resource` that is embedded!).
+To be able to interact with the inspector dock, your ``MyInspectorPlugin.gd`` script
+must extend the :ref:`class_EditorInspectorPlugin` class. This class provides 
+several virtual methods that can be implemented to affect the way the inspector 
+is handling properties.
+
+To have any effect at all the script must implement the ``can_handle()`` method. This
+function is called for each edited :ref:`class_Object` and must return ``true`` if 
+this plugin should handle the object or its properties (including any :ref:`class_Resource`
+that is embedded!).
 
-Once enabled, EditorInspectorPlugin has methods that allow for adding
-:ref:`class_EditorProperty` nodes or just custom :ref:`class_Control` nodes to
-the beginning and end of the inspector for that :ref:`class_Object`, or for
-overriding or changing existing property editors.
+There are 4 other methods that can be implemented to add controls to the inspector at
+specific positions. The ``parse_begin()`` and ``parse_end()`` functions are called only once
+at the beginning and the end of parsing for each object, respectively. They can be used to
+add controls at the very top or very bottom of the inspector layout with ``add_custom_control``.
+
+As the object is parsed the ``parse_category()`` and ``parse_property()`` functions are 
+called. In addition to ``add_custom_control`` both ``add_property_editor`` and 
+``add_property_editor_for_multiple_properties`` can be utilized. These methods are used
+specifically to add :ref:`class_EditorProperty`-based controls.
 
 .. tabs::
  .. code-tab:: gdscript GDScript
@@ -58,71 +84,98 @@ overriding or changing existing property editors.
     # MyInspectorPlugin.gd
     extends EditorInspectorPlugin
 
+    var RandomIntEditor = preload("res://addons/my_inspector_plugin/RandomIntEditor.gd")
+
 
     func can_handle(object):
-        # Here you can specify which object types (classes) should be handled by
-        # this plugin. For example if the plugin is specific to your player
-        # class defined with `class_name MyPlayer`, you can do:
-        # `return object is MyPlayer`
-        # In this example we'll support all objects, so:
+        # We will support all objects in this example.
         return true
 
 
     func parse_property(object, type, path, hint, hint_text, usage):
         # We will handle properties of type integer.
         if type == TYPE_INT:
-            # Register *an instance* of the custom property editor that we'll define next.
-            add_property_editor(path, MyIntEditor.new())
-            # We return `true` to notify the inspector that we'll be handling
-            # this integer property, so it doesn't need to parse other plugins
-            # (including built-in ones) for an appropriate editor.
+            # Create an instance of the custom property editor and register
+            # it to a specific property path.
+            add_property_editor(path, RandomIntEditor.new())
+            # Inform the editor to remove the default property editor for 
+            # this property type.
             return true
         else:
             return false
 
+
 EditorProperty
 --------------
 
-Next, we define the actual :ref:`class_EditorProperty` custom value editor that
-we want instantiated to edit integers. This is a custom :ref:`class_Control` and
-we can add any kinds of additional nodes to make advanced widgets to embed in
-the inspector.
+The :ref:`class_EditorProperty` class is a special type of :ref:`class_Control` that
+can interact with edited objects inside of the inspector dock. By itself it doesn't
+display anything, but can house any other control nodes, including complex
+scenes.
+
+There are three essential parts to the script extending :ref:`class_EditorProperty`:
+
+1. There must be the ``_init`` method that sets up the node structure of the control.
+
+2. The ``update_property()`` method should be implemented to handle changes to the 
+   data from the outside.
+
+3. A signal must be emitted at some point to inform the inspector that the control has
+   changed the property using ``emit_changed``.
+
+You can display your custom widget in two ways. Use the default ``add_child`` method
+to display it to the right of the property name, and ``set_bottom_editor`` to position
+it below the name.
 
 .. tabs::
  .. code-tab:: gdscript GDScript
 
-    # MyIntEditor.gd
+    # RandomIntEditor.gd
     extends EditorProperty
-    class_name MyIntEditor
 
 
+    # The main control for editing the property.
+    var property_control = Button.new()
+    # An internal value of the property.
+    var current_value = 0
+    # A guard against internal changes when the property is updated.
     var updating = false
-    var spin = EditorSpinSlider.new()
 
 
     func _init():
-       # We'll add an EditorSpinSlider control, which is the same that the
-       # inspector already uses for integer and float edition.
-       # If you want to put the editor below the property name, use:
-       # `set_bottom_editor(spin)`
-       # Otherwise to put it inline with the property name use:
-       add_child(spin)
-       # To remember focus when selected back:
-       add_focusable(spin)
-       # Setup the EditorSpinSlider
-       spin.set_min(0)
-       spin.set_max(1000)
-       spin.connect("value_changed", self, "_spin_changed")
-
-
-    func _spin_changed(value):
+        # Add the control as a direct child of EditorProperty node.
+        add_child(property_control)
+        # Make sure the control is able to retain the focus.
+        add_focusable(property_control)
+        # Setup the initial state and connect to the signal to track changes.
+        property_control.text = "Value: " + str(current_value)
+        property_control.connect("pressed", self, "_on_button_pressed")
+
+
+    func _on_button_pressed():
+        # Ignore the signal if the property is currently being updated.
         if (updating):
             return
-        emit_changed(get_edited_property(), value)
+        
+        # Generate a new random integer between 0 and 99.
+        current_value = randi() % 100
+        property_control.text = "Value: " + str(current_value)
+        emit_changed(get_edited_property(), current_value)
 
 
     func update_property():
+        # Read the current value from the property.
         var new_value = get_edited_object()[get_edited_property()]
+        if (new_value == current_value):
+            return
+        
+        # Update the control with the new value.
         updating = true
-        spin.set_value(new_value)
+        current_value = new_value
+        property_control.text = "Value: " + str(current_value)
         updating = false
+
+
+Using the example code above you should be able to make a custom widget
+that replaces the default :ref:`class_SpinBox` control for integers with
+a :ref:`class_Button` that generates random values.