i suppose its DrawPrimitive, but i have no idea how to assign a delay for disappearing and such.
Easiest will be to prepare array where you can hold data for
DrawPrimitive() and a timestamp when effect is supposed to disappear. On each
render_iface() call, iterate thru that array and simply draw a line from cached data. After that, check if current time >= timestamp; if it is, remove element from array.
As for creating line data, simply collect
GetHexPos() for attacker and target; it's drawn for very short time in your example, so you won't need corrections in case of attacker/target movement. I guess render time shouldn't be longer than attack/damage animation time, whichever is shorter.
