Workaround
Try to disable your platform specific pointer acceleration while playing, until this issue is addressed.
The bug
Prior to the 1.14.3 update, the amount of mouse acceleration when playing the game has been almost non-existent. But when i logged on just a few hours ago i could instantly tell something was wrong. The mouse acceleration had been turned up greatly which made my playing experience a lot less enjoyable.
I tried logging on the 1.14.2 update, and there everything was as usual. I then got back on the 1.14.3 update and the problem was still there.
There's nowhere in the settings that says anything about mouse acceleration neither in the 1.14.2 nor the 1.14.3 update.
I'm not sure if there's something wrong on my end but it sure is strange and really annoying.
Explanation
Possibly caused by the recent update of lwjgl explained in this comment.
Linked issues
is duplicated by 7
relates to 1
Comments 24
it's a workaround at most. only devs can fix the issue of course. at least we know the probable cause now.
I am also experiencing this on Ubuntu Gnome 16.04 (running Gnome Shell 3.18), but it seems to be platform-independent, so that information likely doesn't help.
It's pretty obvious to me that raw mouse input, as was used previous in 1.14.2 and below, is no longer being used in 1.14.3.
The only people that would be unaffected by this bug are those who were already using a flat pointer acceleration curve globally.
So, the workaround for this–as found by a user above, and until raw input is supported again as it was before–is disabling mouse acceleration altogether, and comes at the cost of pointer speed while using GUIs like inventory, trading, enchanting, etc. Fullscreen vs windowed, depending on the platform, can also affect pointer behavior, as was described by another user above.
I really hope this was an accident, because if a decision was actually made to remove support for raw mouse input, it was a phenomenally misguided one.
EDIT: For those like me on Linux and still using X11 (not Wayland), the following command will get your current pointer acceleration curve:
xset q | grep -A 1 Pointer
Its output will look something like:
Pointer Control:
acceleration: X/Y threshold: Z
You can then disable (and later re-enable) acceleration with the following commands, making sure that X, Y, and Z correspond to your curve from before. (Note the 0 instead of X in the first command; this is what disables acceleration.)
xset m 0/Y Z
xset m X/Y Z
Probably caused by the latest update of glfw in version 3.3, which now allows the toggle of raw mouse input, and make platform specific pointer acceleration enabled by default.
I believe I have noticed this as well. As I have been trying out 1.14.3 I find that movement is a little "jerky" and I can end up turning/facing directions I had not intended.