patch 8.1.1884: cannot use mouse scroll wheel in popup in Insert mode commit https://github.com/vim/vim/commit/f0bc15c769b60f472d411b3ef98d57db510113c1 Author: Bram Moolenaar <Bram@vim.org> Date: Sun Aug 18 19:23:45 2019 +0200 patch 8.1.1884: cannot use mouse scroll wheel in popup in Insert mode Problem: Cannot use mouse scroll wheel in popup in Insert mode. Mouse clicks in popup close the popup menu. Solution: Check if the mouse is in a popup window. Do not let mouse events close the popup menu. (closes #4544)

" Simplistic way to make spaces and Tabs visible

" This can be added to an already active syntax.

syn match Space " "
syn match Tab "\t"
if &background == "dark"
  hi def Space ctermbg=darkred guibg=#500000
  hi def Tab ctermbg=darkgreen guibg=#003000
else
  hi def Space ctermbg=lightred guibg=#ffd0d0
  hi def Tab ctermbg=lightgreen guibg=#d0ffd0
endif