feat: complete controller-first menu navigation

tests/controller_focus_presentation_validation.gd

@@ -0,0 +1,75 @@
+extends SceneTree
+
+const FocusPresentationType = preload(
+	"res://ui/controller_focus_presentation.gd"
+)
+
+var _failures: Array[String] = []
+
+
+func _initialize() -> void:
+	_run.call_deferred()
+
+
+func _run() -> void:
+	var stage := Control.new()
+	stage.set_anchors_and_offsets_preset(Control.PRESET_FULL_RECT)
+	root.add_child(stage)
+	var presentation := FocusPresentationType.new()
+	stage.add_child(presentation)
+	var standard_button := Button.new()
+	standard_button.text = "standard"
+	standard_button.custom_minimum_size = Vector2(120.0, 60.0)
+	stage.add_child(standard_button)
+	var authored_selector := Button.new()
+	authored_selector.text = "authored selector"
+	authored_selector.position = Vector2(140.0, 0.0)
+	authored_selector.custom_minimum_size = Vector2(160.0, 60.0)
+	authored_selector.set_meta(&"controller_focus_inversion_disabled", true)
+	stage.add_child(authored_selector)
+	await process_frame
+
+	var controller_event := InputEventJoypadButton.new()
+	controller_event.button_index = JOY_BUTTON_A
+	controller_event.pressed = true
+	presentation._input(controller_event)
+	standard_button.grab_focus()
+	await process_frame
+	_expect(
+		standard_button.material != null,
+		"ordinary controller focus receives inversion",
+	)
+
+	authored_selector.grab_focus()
+	await process_frame
+	_expect(
+		standard_button.material == null,
+		"inversion clears when focus moves",
+	)
+	_expect(
+		authored_selector.material == null,
+		"authored selector backgrounds opt out of inversion",
+	)
+
+	standard_button.grab_focus()
+	await process_frame
+	standard_button.focus_mode = Control.FOCUS_NONE
+	await process_frame
+	_expect(
+		standard_button.material == null,
+		"inversion clears when a focused control is defocused",
+	)
+
+	stage.queue_free()
+	if _failures.is_empty():
+		print("Controller focus presentation validation: PASS")
+		quit(0)
+		return
+	for failure: String in _failures:
+		push_error(failure)
+	quit(1)
+
+
+func _expect(condition: bool, message: String) -> void:
+	if not condition:
+		_failures.append(message)