Investigate legacy rendering protocol issues

[jgehrig]

We should investigate the behavior of the legacy rendering protocol to see if it is broken in neovim-qt and/or neovim.

We've defaulted to ext_linegrid=true in a recent commit, #1021.

Several users have noted issues lately:
#1028
#1003
#993

[przepompownia]

I managed to catch some redraw bug with a simpler environment:

nvim-qt-redraw.mp4

On stderr I see:

init.lua:

local root = vim.fn.fnamemodify("./.repro", ":p")

-- set stdpaths to use .repro
for _, name in ipairs({ "config", "data", "state", "cache" }) do
  vim.env[("XDG_%s_HOME"):format(name:upper())] = root .. "/" .. name
end

-- bootstrap lazy
local lazypath = root .. "/plugins/lazy.nvim"
if not vim.loop.fs_stat(lazypath) then
  vim.fn.system({
    "git",
    "clone",
    "--filter=blob:none",
    "--single-branch",
    "https://github.com/folke/lazy.nvim.git",
    lazypath,
  })
end
vim.opt.runtimepath:prepend(lazypath)

-- install plugins
local plugins = {
  {
  'TimUntersberger/neogit',
    dependencies = {
      'nvim-lua/plenary.nvim',
    },
  },
  "folke/tokyonight.nvim",
  {
    "folke/noice.nvim",
    dependencies = {
      "MunifTanjim/nui.nvim",
    },
  },
}
require("lazy").setup(plugins, {
  root = root .. "/plugins",
})

-- add anything else here
vim.opt.termguicolors = true
vim.cmd([[colorscheme tokyonight]])
require('noice').setup({
  messages = {
    view = 'mini',
    view_search = false,
    view_error = 'mini',
    view_warn = 'mini',
  },
  notify = {
    enabled = true,
    view = 'mini',
  },
  lsp = {
    override = {
    },
    signature = {
      enabled = true,
      auto_open = {
        enabled = true,
        trigger = true,
        luasnip = true,
        throttle = 50,
      },
      view = nil,
    },
    hover = {
      enabled = false,
      view = nil,
      ---@type NoiceViewOptions
      opts = {},
    },
  },
  views = {
    mini = {
      timeout = 5000,
    },
  },
  presets = {
    lsp_doc_border = true,
  },
})

local neogit = require('neogit')

neogit.setup {
  -- disable_builtin_notifications = true,
  -- disable_commit_confirmation = true,
}

Reproduction in some git project:

• nvim-qt --nvim /path/to/nvim -- -u init.lua
• add something to stage
• :Neogit commit
• Press c to open gitcommit buffer
• type some existing word, e.g. mess and <C-p> to complete from buffer words
• type any visible character, e.g. :
• for me message become visible just after switching to Normal mode and refreshing the view by <C-l>.

I cannot reproduce it on a fresh buffer containing one word.