Returns the x position of the left edge of the screen, in absolute stage coordinates.
Format: LeftEdge
Arguments:
Return type: float
Error conditions: none
Notes:
This trigger is equivalent to the expression "CameraPos X - GameWidth / 2".
Example:
trigger1 = Pos X + CameraPos X < LeftEdge
; Triggers if the player is to the left of the left edge of the screen.