I did not do touch input in ages, so i am not sure if this is possible:
Create your own custom widgets, do umg only with two layers:
- backgroud layer, some very basic container, border etc.
- second layer where all custom widgets will be placed
Each custom widget knows its anchors (you probably need to set them up from parent)
and it knows its own size, you also can give it resolution of screen
so widget can determine its own coordinates on screen. This is doable if you do not have multiple nested widgets with different aliments etc. I think this is also reason why there is no function to get screen coordinates.
for recalculating position on screen and touch input, there is aspect ratio and sometimes it was different between screen/widgets resolution and touch input resolution.