Pointer Event: Boundary compatibility events for multiple primary pointers
When more than one primary pointers are active, each will have an independent sequence of pointer boundary events but the compatibilty mouse boundary events have their own sequence.
Instruction:
Move the mouse directly into Target0 (without going through Target1), and then leave the mouse there unmoved.
Tap directly on Target1 with a finger or a stylus, and then lift the finger/stylus off the screen/digitizer without crossing Target1 boundary.
Move the mouse into Target0 (if not there already) and move inside it.