Neovim-nightly: mouse selection seems to be broken

I am using neovim with mouse=a and I’ve recently noticed that selection is a bit broken. This appears to be related to how mouse offsets are handled:

  • if I have a single buffer open and nothing else, selection works as expected
  • if I have two buffers open, trying to select content in the rightmost buffer creates a selection area whose width is equal to the current selection plus the width of the left buffer.

This seems to be a recent regression, I am using nightly:

$ nvim --version
NVIM v0.6.0-dev
Build type: Release
LuaJIT 2.1.0-beta3
Compiled by nixbld

Features: +acl +iconv +tui
See ":help feature-compile"

   system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "

I just wanted to confirm here before opening an issue on github. Thanks.