[enhancement] add support to option `floating_window_off_y` as a function

[yao-weijie]

In current version, it's difficult to avoid conflict between lsp_signature.nvim and nvim-cmp, especially when the cursor at the top or bottom of window, I found a solution to solve this problem.

• my config:

  
  local function offsety()
  local linenr = vim.api.nvim_win_get_cursor(0)[1] -- buf line number
  local pumheight = vim.o.pumheight -- my default 10
  local winline = vim.fn.winline() -- line number in the window
  local winheight = vim.fn.winheight(0)
  
  -- window top
  if linenr < pumheight then
      return pumheight
  end
  
  -- window bottom
  if winheight - winline < pumheight then
      return -pumheight
  end
  
  return 0
  end

lsp_signature.setup({ ...

floating_window = true,
floating_window_above_cur_line = false,
floating_window_off_x = 0,
floating_window_off_y = offsety,

...

})

- modification
modify `lsp_signature.nvim/lua/init.lua`
![图片](https://user-images.githubusercontent.com/36393630/206346358-c316b4b0-440c-42db-86d7-7cecc2984b5f.png)

- final effect
  - at window top

![图片](https://user-images.githubusercontent.com/36393630/206346868-85eebe9d-7b05-4614-b186-9f7b477fdb5b.png)

  - at window bottom

![图片](https://user-images.githubusercontent.com/36393630/206347054-efc701eb-a49c-4a95-ab7d-0789a2650949.png)

  - at window middle area

![图片](https://user-images.githubusercontent.com/36393630/206347156-7438f8c7-345b-45c4-8d57-5921c6fed2ae.png)

- requirements
  the window is high enough, and it's better not to split horizontal :)

[ray-x]

Thanks for your suggestions. I pushed a commit based on your code snippets.

[ray-x]

@yao-weijie Could you check if it works for you. Also when you happy, please share your offset_x/y function setup.

[yao-weijie]

I replied the mail but it seems that you didn't received it. :(

The patch works (I used the offset_y function as you put in README). And I think there are some auxiliary options is important.

" better to set the two options the same
set scrolloff=10 " 
set pumheight=10 " max height of cmp menu

" lsp_signature option
" if set to false, it may still conflict with cmp at middle of window
floating_window_above_cur_line = true

I think there is still some points to improve the floating window experience. Look at the img:

If it is possible to pass a parameter to the offset_x/y function that contains the floating window size (especially height) like this? Then I think the signature help will be perfect!

[ray-x]

I am wondering how you want to pass in the opts? How about this I add a new options

setup{
  ...
  floating_opts=function() return {} end,
  ...
}

So in offset_x you can do this:

offset_x(floating_opts())

[yao-weijie]

setup{ floating_window_off_y = function(opts) ... end }

the opts contains the signature help window size. Actually I'm not sure of the process of generating the help window. If help window size is calculated before offset_y, then you can pass the size to the offset_y function.

[ray-x]

I pushed another change to allow floating_opts been passed to off_x/y. Would you take a look?