Inventory2/ui/Menu.cs

public partial class Menu : CenterContainer
{
	[Export] public Container SideButtons { get; set; }
	[Export] public TabContainer Tabs { get; set; }

	public override void _Ready()
	{
		foreach (var child in SideButtons.GetChildren())
			if ((child is BaseButton button) && button.ToggleMode)
				button.Pressed += () => {
					for (var i = 0; i < Tabs.GetTabCount(); i++)
						if (Tabs.GetTabControl(i).Name == button.Name)
							Tabs.CurrentTab = i;
					// Make sure you can't "detoggle" the button.
					button.Disabled = true;
				};
	}

	public override void _Input(InputEvent @event)
	{
		if (!Visible) {
			var isMouseCaptured = Input.MouseMode == Input.MouseModeEnum.Captured;
			if (!isMouseCaptured && @event.IsActionPressed("ui_cancel")) {
				Visible = true;
				GetViewport().SetInputAsHandled();
			}
			return;
		}

		if (@event.IsActionPressed("ui_cancel")) {
			OnReturnPressed();
			GetViewport().SetInputAsHandled();
		}
	}

	public void OnTabChanged(int tabIndex)
	{
		var tabName = Tabs.GetTabControl(tabIndex).Name;
		foreach (var child in SideButtons.GetChildren())
			if ((child is BaseButton button) && button.ToggleMode)
				button.Disabled = button.ButtonPressed = button.Name == tabName;
	}

	public void OnReturnPressed()
	{
		Visible = false;
	}

	public void OnQuitPressed()
	{
		GetTree().Quit();
	}
}