When the Minecraft window is resized while still ingame (and the center of the window changes), the player will start to spin until a GUI is opened and closed. The player can still move the mouse / use the movement keys / place blocks, but they will spin while doing so.
The only way to resize the window while keeping ingame focus is by using the WindowsKey + ArrowKey shortcuts.
1. Move the Minecraft window to the left side of the screen with WindowsKey + Left. This will put the window fully vertically on the side, and will resize the window.
2. Put the mouse back into the Minecraft window.
3. Move the window back to the center with WindowsKey + Right.
4. You will experience this bug.
(For extra fun, run /effect @p minecraft:nausea before hand, but this is not needed).
I believe that the root cause of this issue is that the "Center of the screen" location that the mouse jumps to each tick isn't getting updated on screen resize properly, but the location that is used to compute the movement of the mouse is.
Comments 6
Confirmed for
15w50a with Windows 7
The reason for that might be that Minecraft has still focus while the mouse position is changing (at least LWJGL claims that).
As of 1.12.2-pre1 (and Windows Insider Preview build 10.0.16278.1000), this is behaving different: it only rotates when I move the mouse, although the area where the mouse is captured is still not updated. So no constant spinning, but it's still broken.
This is probably an LWJGL issue regarding mouse grabbing.
Confirmed with Windows 7