The rectangles corner radii are limited to half the width and half the height. This made sense when all radii had to be the same before https://codereview.qt-project.org/c/qt/qtdeclarative/+/477301.

However, since radii can be set individually, we can relax this limit to something like

upper-left radius + upper-right radius < width
upper-left radius + lower-left radius < height
and so on...

This increases the flexibility of rectangle substantially without increasing the code complexity.