Improve Scene Tree editor performance

We now cache the Node*<>TreeItem* mapping in the SceneTreeEditor. This
allows us to make targeted updates to the Tree used to display the scene
tree in the editor.

Previously on almost all changes to the scene tree the editor would
rebuild the entire widget, causing a large number of deallocations an
allocations. We now carefully manipulate the Tree widget in-situ saving
a large number of these allocations.

In order to know what Nodes need to be updated we add a
editor_state_changed signal to Node, this is a TOOLS_ENABLED,
editor-only signal fired when changes to Node happen that are relevant
to editor state.

We also now make sure that when nodes are moved/renamed we don't check
expensive properties that cannot contain NodePaths. This saves a lot of
time when SceneTreeDock renames a node in a scene with a lot of
MeshInstances. This makes renaming nodes go from ~27 seconds to ~2
seconds on large scenes.

SceneTreeEditor instances will now also not do all of the potentially
expensive update work if they are invisible. This behavior is turned off
by default so it won't affect existing users. This change allows the
editor to only update SceneTreeEditors that actually in view. In
practice this means that for most changes instead of updating 6
SceneTreeEditors we only update 1 instantly, and the others only when
they become visible.

There is definitely more that could be done, but this is already a
massive improvement. In complex scenes we see an improvement of 10x,
things that used to take ~30 seconds now only take 2.

This fixes #83460

I want to thank KoBeWi, TokisanGames, a-johnston, aniel080400 for
their tireless testing. And AeioMuch for their testing and providing a
fix for the hover issue.

Author: hpvb

core/object/object.h

@@ -89,6 +89,7 @@ enum PropertyHint {
 	PROPERTY_HINT_DICTIONARY_TYPE,
 	PROPERTY_HINT_TOOL_BUTTON,
 	PROPERTY_HINT_ONESHOT, ///< the property will be changed by self after setting, such as AudioStreamPlayer.playing, Particles.emitting.
+	PROPERTY_HINT_NO_NODEPATH, /// < this property will not contain a NodePath, regardless of type (Array, Dictionary, List, etc.). Needed for SceneTreeDock.
 	PROPERTY_HINT_MAX,
 };
 

doc/classes/@GlobalScope.xml

@@ -2943,7 +2943,7 @@
 		<constant name="PROPERTY_HINT_ONESHOT" value="40" enum="PropertyHint">
 			Hints that a property will be changed on its own after setting, such as [member AudioStreamPlayer.playing] or [member GPUParticles3D.emitting].
 		</constant>
-		<constant name="PROPERTY_HINT_MAX" value="41" enum="PropertyHint">
+		<constant name="PROPERTY_HINT_MAX" value="42" enum="PropertyHint">
 			Represents the size of the [enum PropertyHint] enum.
 		</constant>
 		<constant name="PROPERTY_USAGE_NONE" value="0" enum="PropertyUsageFlags" is_bitfield="true">

doc/classes/Node.xml

@@ -1068,6 +1068,11 @@
 				Emitted when the node's editor description field changed.
 			</description>
 		</signal>
+		<signal name="editor_state_changed">
+			<description>
+				Emitted when an attribute of the node that is relevant to the editor is changed. Only emitted in the editor.
+			</description>
+		</signal>
 		<signal name="ready">
 			<description>
 				Emitted when the node is considered ready, after [method _ready] is called.

doc/classes/TreeItem.xml

@@ -36,6 +36,12 @@
 				Calls the [param method] on the actual TreeItem and its children recursively. Pass parameters as a comma separated list.
 			</description>
 		</method>
+		<method name="clear_buttons">
+			<return type="void" />
+			<description>
+				Removes all buttons from all columns of this item.
+			</description>
+		</method>
 		<method name="clear_custom_bg_color">
 			<return type="void" />
 			<param index="0" name="column" type="int" />

editor/connections_dialog.cpp

@@ -735,6 +735,7 @@ ConnectDialog::ConnectDialog() {
 	from_signal->set_editable(false);
 
 	tree = memnew(SceneTreeEditor(false));
+	tree->set_update_when_invisible(false);
 	tree->set_connecting_signal(true);
 	tree->set_show_enabled_subscene(true);
 	tree->set_v_size_flags(Control::SIZE_FILL | Control::SIZE_EXPAND);