Context uses WidgetRects to store the rectangles of all widgets from the previous frame. Context::interact uses this to check that no tother widget is covering the current widget.

This code could be simplified by doing the hit-test once at the start of the frame, using the WidgetRects from the previous frame.

With full knowledge, we could to a smart hit-test where we look for all widget within a certain small radius of the pointer, and hover/click/drag the closest one. This allows for slightly bigger hit-boxes, making things easier to click. This could replace the current hack of growing hit boxes by item_spacing / 2.

Note that we needs to find the top widget for clicks and for drags separately, because the top widget that is click-sensitive (e.g. a button) can be different from the top widget that is drag-sensitive (e.g. a ScrollArea).