ZDoom

BlockLinesIterator is already in.

[s]I think this can already be done modder-side with some LineTracers and a thinker.[/s]
EDIT: yes, [url=https://github.com/coelckers/gzdoom/blob/bcef4405119bbeccd2082caec6a8ae4a5f019636/wadsrc/static/zscript/base.zs#L551]BlockLinesIterator[/url] since it appears only to check the lines in a given area rather than having to go through the entire map every time.

for iterating through multiple simultaneous BlockingLines, mainly for normalizing the angle results on corner collisions
because currently (ex bouncing projectiles) can take one line of a corner and use it for calculating the bounce, even if its more to the other side of said corner, and trying to bounce away from the farther one gets clipped inside the wall