[WIP] Add "Follow Selection" in the 3D editor by using Center Selecti…

…on twice

When pressing the Center Selection shortcut twice, you will begin following
the current selection. This also applies to selection changes.

The effect is undone by pressing the Center Selection shortcut another
time, or by panning/using freelook on the 3D editor camera. (Orbiting
does not undo the effect.)

TODO:

- Add a visual indicator when following is enabled.
- Modify tooltips and possibly menu action names to document the functionality.

editor/plugins/node_3d_editor_plugin.cpp

@@ -2364,7 +2364,9 @@ void Node3DEditorViewport::_sinput(const Ref<InputEvent> &p_event) {
 			_menu_option(VIEW_CENTER_TO_ORIGIN);
 		}
 		if (ED_IS_SHORTCUT("spatial_editor/focus_selection", p_event)) {
+			print_line("Centering to selection. Times focused consecutively: ", times_focused_consecutively);
 			_menu_option(VIEW_CENTER_TO_SELECTION);
+			times_focused_consecutively += 1;
 		}
 		if (ED_IS_SHORTCUT("spatial_editor/align_transform_with_view", p_event)) {
 			_menu_option(VIEW_ALIGN_TRANSFORM_WITH_VIEW);
@@ -2519,6 +2521,9 @@ void Node3DEditorViewport::_nav_pan(Ref<InputEventWithModifiers> p_event, const
 	translation *= cursor.distance / DISTANCE_DEFAULT;
 	camera_transform.translate_local(translation);
 	cursor.pos = camera_transform.origin;
+
+	print_line("Pan: Resetting times focused consecutively to 0.");
+	times_focused_consecutively = 0;
 }
 
 void Node3DEditorViewport::_nav_zoom(Ref<InputEventWithModifiers> p_event, const Vector2 &p_relative) {
@@ -2781,6 +2786,9 @@ void Node3DEditorViewport::_update_freelook(real_t delta) {
 	const Vector3 motion = direction * speed * delta;
 	cursor.pos += motion;
 	cursor.eye_pos += motion;
+
+	print_line("Freelook: Resetting times focused consecutively to 0.");
+	times_focused_consecutively = 0;
 }
 
 void Node3DEditorViewport::set_message(const String &p_message, float p_time) {
@@ -2892,6 +2900,11 @@ void Node3DEditorViewport::_notification(int p_what) {
 			_update_navigation_controls_visibility();
 			_update_freelook(delta);
 
+			if (times_focused_consecutively >= 2 && times_focused_consecutively % 2 == 0) {
+				print_line("[Follow] Centering to selection. Times focused consecutively: ", times_focused_consecutively);
+				_menu_option(VIEW_CENTER_TO_SELECTION);
+			}
+
 			Node *scene_root = SceneTreeDock::get_singleton()->get_editor_data()->get_edited_scene_root();
 			if (previewing_cinema && scene_root != nullptr) {
 				Camera3D *cam = scene_root->get_viewport()->get_camera_3d();

editor/plugins/node_3d_editor_plugin.h

@@ -525,6 +525,8 @@ class Node3DEditorViewport : public Control {
 
 	void focus_selection();
 
+	int times_focused_consecutively = 0;
+
 	void assign_pending_data_pointers(
 			Node3D *p_preview_node,
 			AABB *p_preview_bounds,