Is there any workaround for the issue where the mouse and keyboard become almost uncontrollably laggy in the debugger after hitting a break point?

Is your system running out of resources (CPU, memory, etc) when this happens?

Calling it an issue seems wrong as this is the first I've ever heard of that. If the mouse and keyboard are having problems it's not because of allegro but because of visual studio. When a breakpoint is hit, all the threads are stopped, including any input threads. It's your system having the issue, not allegro.

Grab the copy from git (branch 4.4) , this has been fixed there.

Okay, guess I was wrong.

What was wrong with allegro that made Visual Studio have problems? And how did you ever figure out what was causing it?

Wasn't me, it was Yamakuzure. No idea how he figured it out .

I looked at the patches and I can't see what is in there that would affect this. Do you know which parts of the patch fixed this?

GUID_SysMouseEm2 and GUID_SysKeyboardEm2 apparently do the trick. I don't know why or how.

The main ones are probably exclusive access, and the Em are not.

It turns out that the patch doesn't fix the kb/mouse lag. Yamakuzure acknowledged this in his last post but it wasn't entirely clear, so I had already tried out the patch.