game/user_interface/button_selection.gd

@tool
class_name ItemSelection extends HFlowContainer

##
## An item has been selected via GUI selection or [method select_item].
##
signal item_selected(index: int)

var _button_group := ButtonGroup.new()

##
## Number of items in the selection.
##
var item_count: int:
	get:
		return _button_group.get_buttons().size()

func _get_configuration_warnings() -> PackedStringArray:
	var warnings := PackedStringArray()
	var children := get_children()

	if not(children.is_empty()):
		var self_class_name := get_class()

		for child in get_children():
			warnings.append(
				"{0} can only have Button children, but {1} is of type {2}".format(
					[self_class_name, child.name, child.get_class()]))

	return warnings

##
## Adds a new item with no text and only [code]icon[/code] as the icon to the selection.
##
func add_icon_item(icon: Texture2D) -> void:
	var child_count := get_child_count()
	var button := Button.new()

	button.icon = icon
	button.icon_alignment = HORIZONTAL_ALIGNMENT_CENTER
	button.toggle_mode = true
	button.button_group = _button_group
	button.button_pressed = child_count == 0

	button.pressed.connect(func () -> void: select_item(child_count))
	add_child(button)

##
## Returns the icon used by the item at [code]index[/code].
##
## An assertion is raised if [code]index[/code] is out of bounds from the item count.
##
func get_item_icon(index: int) -> Texture2D:
	var buttons := _button_group.get_buttons()

	assert(index < buttons.size(), "index out of range")

	var button := buttons[index] as Button

	return null if (button == null) else button.icon

##
## Returns the currently selected item index or [code]-1[/code] if no item is selected. 
##
func get_selected_item() -> int:
	var pressed_button := _button_group.get_pressed_button()

	return -1 if (pressed_button == null) else pressed_button.get_index()

##
## Selects the item at [code]index[/code], emitting [signal item_selected] at the end.
##
## An assertion is raised if [code]index[/code] is out of bounds from the item count.
##
func select_item(index: int) -> void:
	var buttons := _button_group.get_buttons()

	assert(index < buttons.size(), "index out of range")

	var pressed_button := _button_group.get_pressed_button()

	if pressed_button != null:
		pressed_button.set_pressed_no_signal(false)

	buttons[index].set_pressed_no_signal(true)
	item_selected.emit(index)