Here are some examples of using `isEmpty`:c++ LayoutRect rect1(10, 20, 0, 0); if (rect1.isEmpty()) { std::cout << "rect1 is empty" << std::endl; } LayoutRect rect2(30, 40, 50, 60); if (!rect2.isEmpty()) { std::cout << "rect2 is not empty" << std::endl; } ``` In the first example, `rect1` is created with zero width and height, so `isEmpty` will return true. In the second example, `rect2` has non-zero width and height, so `isEmpty` returns false. As for the package or library that `LayoutRect` belongs to, it is most likely part of a larger GUI or layout library or framework, such as Qt or wxWidgets. However, without more context or information, it is difficult to determine the exact package or library.