patch 8.1.1751: when redrawing popups plines_win() may be called often commit https://github.com/vim/vim/commit/9d5ffceb3fea247a88d4d3936e97b7f488aab6ff Author: Bram Moolenaar <Bram@vim.org> Date: Fri Jul 26 21:01:29 2019 +0200 patch 8.1.1751: when redrawing popups plines_win() may be called often Problem: When redrawing popups plines_win() may be called often. Solution: Pass a cache to mouse_comp_pos().

func Test_empty_buffer()
  new
  insert
a
b
c
d
.
  call assert_equal(1, line("''"))
  bwipe!
endfunc