If your map render the data on the fly, and your screen is so big, that means it contains many tiles, each tile need use some CPU source so it's slow.
I guess you can do something to handle it:
- Increase the tile size
- Open cache and the 2nd time the same tile render will directly read the cached image but not render the data
- Change the drawing mode to high speed and see whether it can reduce the CPU usage
I will let our developer know your requirement, and maybe we can do special optimize for very large resolution in future.