Let's say you have a Google Maps like draggable map:
I'd like to show the user that there is something waiting for him somewhere outside of the visible portion of the map, let's say to the left. My instinct would tell me to overlay an arrow, but this has a few problems:
If I respect the interface controls like in the image above, then it's not evidently clear for the user whether he's supposed to scroll to the left or interact with the zooming controls which the arrow seems to be pointing at aswell. If I disregard the interface instead:
While the intent might be clearer, well, what if the user wants to interact with the zooming controls before reaching the location pointed by the arrow?
In the example I'm providing here the solution might seem easy, just place the arrow somewhere where there are no interface controls; the problem comes when the location I want to point the user to is not predefined, scenario in which, at least in the examples I provide, the arrow would ideally "guess" what is the best place on the screen to appear based on the target location (that is to say, depending on the direction the user should scroll)
What is the best way to let the user know he should scroll in some direction without getting in the way of an existing overlayed interface AND in such a way that it doesn't become ambiguous with said interface?