In css, we can specify a percentage as property value. Will there be something like this in uss? I understand that we have such things as flex-grow, and this is great, but sometimes it becomes necessary to set percentage coordinates, for example position: absolute; left: 50%; If this is not possible, then the next question is how to find out the current size of the parent container? I noticed that it is not calculated immediately, that is, if I set flex-grow and then request layout.width, I won’t get the current width. This is reasonable in terms of performance, but I would like to understand how it can be obtained when it becomes necessary.