[WIP] Introduce floatwin/popupwin compatible layer

[hrsh7th]

This PR aims to discuss the PR #510.

TODO

• Support fenced language highlighting (difficult...).
• Switch output.vim to new implementation.

Please feedback the APIs and below points.

• How to support let g:lsp_preview_float = 0.
• How to support popup-win's border feature.
• Currently implementation always usemarkdown syntax.

[prabirshrestha]

Would be also good to have borders for neovim. Can be in different PR neovim/neovim#9718 (comment)

[clason]

See also https://www.reddit.com/r/neovim/comments/eh397t/a_floating_terminal_plugin_with_border/

[prabirshrestha]

Thanks for sending this PR.

Let us move this to top level utils folder instead of ui/vim. I will be working on refactoring ui/vim/vim.vim into smaller utils. I want to slowly get rid of the ui folder.

Here are some of the api name changes we should do.

let l:floatwin = lsp#utils#floatwin#new({ ... })
call l:floatwin.show(screenpos, lsp#utils#normalize_markup_content(content))
call l:floatwin.hide()
call l:floatwin.enter() " should this be called focus()?
call l:floatwin.is_visible()

call lsp#utils#floatwin#calcaulate_height(contents)
call lsp#utils#floatwin#calcaulate_width(contents)
call lsp#utils#floatwin#screenpos(line, col, bufnr) " do we need bufnr?

[prabirshrestha]

@hrsh7th any updates on this? currently it has merge conflicts.

[hrsh7th]

Sorry, I have forgotten this PR.

Hm... PR has a problem that is missing preview-window feature.

Anyway, I will solve conflicts.

[prabirshrestha]

let us continue the discussion at vim-jp/vital.vim#747 and vim-jp/vital.vim#748.