paging pseudocode

//this checks the pseudo-distance from the edge of the screen
function CheckDistance(region):
	//locations relative to the camera
	x = region.x - camera.x
	y = region.y - camera.y

	//if the region is visible, return 0
	if (-pager.w < x < screen.w) return 0
	if (-pager.h < y < screen.h) return 0

	//prune the screen's area from the algorithm
	if (x > 0) x -= screen.w
	if (x > 0) x -= screen.h

	//get the pseudo-indexes
	x = x / pager.w
	y = y / pager.h

	//return the position-index with the greatest magnitude
	return max(abs(x), abs(y))
end

//prune distant regions
for (it = begin() to end()):
	if (CheckDistance(it) > 2):
		Unload(it)
	end
end

//request empty regions, including buffers (-1 & +1)
for (i = snap(camera.x - pager.w) to snap(camera.x + screen.w + pager.w)):
	for (j = snap(camera.y - pager.h) to snap(camera.y + screen.h + pager.h)):
		if (not pager.Find(i, j)):
			RequestRegion(i, j)
		end
	end
end