DK - King of Swing control bug

[Ixodid]

Tried with 0.5.2 and the latest nightly of mGBA, on windows 10 64-bit.
When grabbing two pegs at the same time your character gets turned around. This makes the game pretty difficult to play as you can't jump up, and even makes the tutorial character that is supposed to show you the ropes screw up all of their jumps.

[endrift]

I'd already gotten this report in an email, but haven't gotten around to looking into it.

Here are the details from the email:

I'm using Windows 8.1 and mGBA 0.5.2 (the latest stable release, as of this writing.)

There is a serious movement orientation bug in DK: King of Swing which makes it difficult to play.

When your character is holding onto a peg with one hand, and tries to grab a peg with the other, they are almost always turned to a different direction than they should. This direction change continues after they let go; the character continues rotating from that direction, as if they had started from that direction to begin with.

After examining the specific cases where there were problems (listed below), the problem appears to be with vertical orientation detection when two pegs are grabbed, where the vertical orientation is reversed once a player grabs a second peg (i.e. if they are supposed to be facing up, they face down, and vice versa). The only case where this doesn't happen is if the character is supposed to be facing down, where they face down (see the bottom of the list below)

The specific errors are (these are demonstrated in the attached .avi file):

• If they are supposed to be facing diagonally left-down, they face left-up.
• If they are supposed to be facing diagonally left-up, they face left-down.
• If they are supposed to be facing up, they face down.
• If they are supposed to be facing diagonally right-up, they face right-down.
• If they are supposed to be facing diagonally right-down, they face right-up.
• They do face down when they are supposed to, but if you look carefully, you can see the sprite face up for a frame.

[endrift]

There was a bug affecting this game that was fixed in 0.5.2, can you check 0.5.1 to see if the behavior is any different? I wonder if I'm hitting some anti-piracy measures.

[Ixodid]

Going back through older releases the last one that works is 0.4.1. It broke somewhere between 0.4.1 and 0.5.0.

[endrift]

That's kind of odd but that information will help me bisect to figure out when it broke. Thanks!

[Ixodid]

I went through the old nightlies just to be a bit more thorough.
Last version that worked: 7401371
In 812d063 the problem is slightly different and DK's right hand can't grab pegs at all, most of the time.
Finally, 7212854 is the first version with the specific issue described above/in your email.
So I'm assuming the problem is with the threaded rendering changes in 812d063 and ac11542.

[endrift]

Ah! This clearly points to the problem being the ArcTan implementation in the HLE BIOS. I wonder what the edge case here is, since my implementation is reversed out of the BIOS.

[endrift]

Thanks for narrowing it down! That saved me a lot of work bughunting.