Single-pixel line not redrawn in vterm

[Vojtech Horky]

The problem is best described by the attached picture.

The bug was initially reported through ​mailing-list, posting excerpt here for quick-reference.

When playing tetris 90 deg rotated, a single-pixel line remains drawn
in previous position of the falling block. Screenshot is attached. But
I am not sure that this is not something related rather to Qemu than
to your server.

I am also not sure. But my guess is that it is caused by off-by-one
error in damage region calculation inside console server. Another
suspect is nearest-neighbor filtering when it is applied on damage
region coordinates. I will look into it when I will resume working
on my thesis, which I have to put aside for some time because of
other commitments. So for now, let's consider it a known issue.

[Vojtech Horky]

Demonstration of the bug (notice window is rotated)

[Jakub Jermář]

Fix merged in mainline,1725.