GetUIParentAnchor

This is a user-defined function that you can copy and paste into your addon.

Returns SetPoint args for the frame, anchor is relative to the nearest corner of the screen.

local function GetUIParentAnchor(frame)
	local w, h, x, y = UIParent:GetWidth(), UIParent:GetHeight(), frame:GetCenter()
	local hhalf, vhalf = (x > w/2) and "RIGHT" or "LEFT", (y > h/2) and "TOP" or "BOTTOM"
	local dx = hhalf == "RIGHT" and math.floor(frame:GetRight() + 0.5) - w or math.floor(frame:GetLeft() + 0.5)
	local dy = vhalf == "TOP" and math.floor(frame:GetTop() + 0.5) - h or math.floor(frame:GetBottom() + 0.5)

	return vhalf..hhalf, dx, dy
end