nvim pager for kitty history

kitty+page.lua

return function(INPUT_LINE_NUMBER, CURSOR_LINE, CURSOR_COLUMN)
  print('kitty sent:', INPUT_LINE_NUMBER, CURSOR_LINE, CURSOR_COLUMN)
  vim.opt.encoding='utf-8'
  vim.opt.clipboard = 'unnamed'
  vim.opt.compatible = false
  vim.opt.number = false
  vim.opt.relativenumber = false
  vim.opt.termguicolors = true
  vim.opt.showmode = false
  vim.opt.ruler = false
  vim.opt.laststatus = 0
  vim.o.cmdheight = 0
  vim.opt.showcmd = false
  vim.opt.scrollback = INPUT_LINE_NUMBER + CURSOR_LINE
  local term_buf = vim.api.nvim_create_buf(true, false);
  local term_io = vim.api.nvim_open_term(term_buf, {})
  vim.api.nvim_buf_set_keymap(term_buf, 'n', 'q', '<Cmd>q<CR>', { })
  vim.api.nvim_buf_set_keymap(term_buf, 'n', '<ESC>', '<Cmd>q<CR>', { })
  local group = vim.api.nvim_create_augroup('kitty+page', {})

  local setCursor = function()
    vim.api.nvim_feedkeys(tostring(INPUT_LINE_NUMBER) .. [[ggzt]], 'n', true)
    local line = vim.api.nvim_buf_line_count(term_buf)
    if (CURSOR_LINE <= line) then
      line = CURSOR_LINE
    end
    vim.api.nvim_feedkeys(tostring(line - 1) .. [[j]], 'n', true)
    vim.api.nvim_feedkeys([[0]], 'n', true)
    vim.api.nvim_feedkeys(tostring(CURSOR_COLUMN - 1) .. [[l]], 'n', true)
  end

  vim.api.nvim_create_autocmd('ModeChanged', {
    group = group,
    buffer = term_buf,
    callback = function()
      local mode = vim.fn.mode()
      if mode == 't' then
        vim.cmd.stopinsert()
        vim.schedule(setCursor)
      end
    end,
  })

  vim.api.nvim_create_autocmd('VimEnter', {
    group = group,
    pattern = '*',
    once = true,
    callback = function(ev)
        local current_win = vim.fn.win_getid()
        for _, line in ipairs(vim.api.nvim_buf_get_lines(ev.buf, 0, -2, false)) do
          vim.api.nvim_chan_send(term_io, line)
          vim.api.nvim_chan_send(term_io, '\r\n')
        end
        for _, line in ipairs(vim.api.nvim_buf_get_lines(ev.buf, -2, -1, false)) do
          vim.api.nvim_chan_send(term_io, line)
        end
        vim.api.nvim_win_set_buf(current_win, term_buf)
        vim.api.nvim_buf_delete(ev.buf, { force = true } )
        vim.schedule(setCursor)
    end
  })
end

kitty.conf

# ...
scrollback_pager nvim -u NONE -R -M -c 'lua require("kitty+page")(INPUT_LINE_NUMBER, CURSOR_LINE, CURSOR_COLUMN)' -  
# ...

I'm using this gist but I'm finding that if the setCursor function is called in the VimEnter autocommand callback it doesnt work properly because the buffer isn't fully written when we try to set the cursor. INPUT_LINE_NUMBER is usually greater than the number of lines in the buffer at that point resulting in the cursor being placed at the very bottom of the buffer.

My hacky solution was to take out the vim.schedule(setCursor) line from the VimEnter callback and put vim.defer_fn(setCursor, 10) at the bottom of the returned function. I basically want to synchronously invoke setCursor AFTER the VimEnter autocommand is complete, and 10ms seems to be enough time for the VimEnter autocommand to finish writing the contents of the buffer. Has anyone else has encountered this? Looking for some guidance on a less hacky approach.

This is my modified attempt, using @yusufshalaby solution with vim.defer_fn(setCursor, 10) to make sure the terminal has time to process the content and the buffer is ready.

/home/YOUR_USER/.config/nvim/lua/kitty+page.lua:

return function(INPUT_LINE_NUMBER)
    vim.opt.encoding='utf-8'
    -- Prevent auto-centering on click
    vim.opt.scrolloff = 0
    vim.opt.compatible = false
    vim.opt.number = false
    vim.opt.relativenumber = false
    vim.opt.termguicolors = true
    vim.opt.showmode = false
    vim.opt.ruler = false
    vim.opt.signcolumn=no
    vim.opt.showtabline=0
    vim.opt.laststatus = 0
    vim.o.cmdheight = 0
    vim.opt.showcmd = false
    vim.opt.scrollback = 100000
    vim.opt.clipboard:append('unnamedplus')
    local term_buf = vim.api.nvim_create_buf(true, false)
    local term_io = vim.api.nvim_open_term(term_buf, {})
    -- Map 'q' to first yank the visual selection (if any), which makes the copy selection work, and then quit.
    vim.api.nvim_buf_set_keymap(term_buf, 'v', 'q', 'y<Cmd>qa!<CR>', { })
    -- Regular quit mapping for normal mode
    vim.api.nvim_buf_set_keymap(term_buf, 'n', 'q', '<Cmd>qa!<CR>', { })
    local group = vim.api.nvim_create_augroup('kitty+page', {clear = true})

    local setCursor = function()
        local max_line_nr = vim.api.nvim_buf_line_count(term_buf)
        local input_line_nr = math.max(1, math.min(tonumber(INPUT_LINE_NUMBER), max_line_nr))

        -- It seems that both the view (view.topline) and the cursor (nvim_win_set_cursor) must be set
        -- for scrolling and cursor positioning to work reliably with terminal buffers.
        vim.fn.winrestview({topline = input_line_nr})
        vim.api.nvim_win_set_cursor(0, {input_line_nr, 0})
    end

  vim.api.nvim_create_autocmd('ModeChanged', {
    group = group,
    buffer = term_buf,
    callback = function()
      local mode = vim.fn.mode()
      if mode == 't' then
        vim.cmd.stopinsert()
        vim.schedule(setCursor)
      end
    end,
  })

  vim.api.nvim_create_autocmd('VimEnter', {
    group = group,
    pattern = '*',
    once = true,
    callback = function(ev)
        local current_win = vim.fn.win_getid()
        -- Instead of sending lines individually, concatenate them.
        local main_lines = vim.api.nvim_buf_get_lines(ev.buf, 0, -2, false)
        local content = table.concat(main_lines, '\r\n')
        vim.api.nvim_chan_send(term_io, content .. '\r\n')

        -- Process the last line separately (without trailing \r\n)
        local last_line = vim.api.nvim_buf_get_lines(ev.buf, -2, -1, false)[1]
        if last_line then
            vim.api.nvim_chan_send(term_io, last_line)
        end
        vim.api.nvim_win_set_buf(current_win, term_buf)
        vim.api.nvim_buf_delete(ev.buf, { force = true } )
        -- Use vim.defer_fn to make sure the terminal has time to process the content and the buffer is ready.
        vim.defer_fn(setCursor, 10)
    end
  })
end

On my kitty.conf:

scrollback_pager nvim -u NONE -R -M -c 'lua require("kitty+page")(INPUT_LINE_NUMBER)' -