CooldownFrame:SetUseCircularEdge()
 

I think this is a new function. Probably made just for the rune bar for deathknights.

From my quick testing is instead of a cooldown having a square border. It has a round border.
Blizzard no longer has to use tricks to fake a real circle cooldown. Hopefully they expand on this and use it in other parts of the games UI.

Is there a way to find new functions added, only stumbled across this one looking at the xml. Then I had to guess what the lua function was. In the xml its called useCircularEdge

I'm liking this a lot, cooldowns have gotten so many new features over the years. Keeps getting better.

Is it unique to the cooldown frame, or could you use it, say, on action buttons, buffs, or other things?

By default, the game uses a square "edge" texture for the cooldown swipe. This is basically just a line that leads/follows the colored swipe and is also used (I think) for the charge cooldowns. Hopefully this is what we think it is so I don't have to hack to make circular swipe edges. :p

@Myrroddin: I imagine it's unique to the Cooldown frame, as is SetSwipeColor, SetSwipTexture, SetEdgeTexture, etc. But action buttons, buffs, etc, typically have a cooldown region inherently, IIRC.

Circular cooldowns are not new. That function might be, but SetSwipeTexture as an example doesn't ignore alpha channel, so you could just use a custom swipe texture that's just a circle and it would chop off the edges. I would hardly call that a hack.

From what I can see, this change doesn't effect the swipe texture, just the edge texture. So instead of the edge texture getting clipped in a square, it gets clipped in a circle.

This can be faked some what on live. That's what they did with the old death knight icons. They have the icon, then the cooldown frame on top of that. Then a ring texture on top of that. With creative use of artwork they are able to hide it. But if you make the icons larger that trick fails and you can see its not really rounded.

This could be useful for ring addons that were already using the cooldown frame. Now you can have better looking spark lines imo.

Not in all cases, no. But if the game actually sets that texture, you'd have to replace or hook the function to keep it from overwriting your changes, hence "hack".

Exactly. For instance, my new skin uses the mask feature for the icons and I managed to get everything *except* the edge texture to be round. Obviously I could do something similar to what I mentioned above, but I'm not certain it would work as intended with a round alpha channel.

With this now live, I've been testing it and it doesn't seem to do anything. :/