autocmd events for open/close floats

autoload/lsp.vim

@@ -25,6 +25,8 @@ augroup _lsp_silent_
     autocmd User lsp_unregister_server silent
     autocmd User lsp_server_init silent
     autocmd User lsp_server_exit silent
+    autocmd User lsp_float_opened silent
+    autocmd User lsp_float_closed silent
 augroup END
 
 function! lsp#log_verbose(...) abort

autoload/lsp/ui/vim/output.vim

@@ -17,6 +17,7 @@ function! lsp#ui#vim#output#closepreview() abort
   endif
   let s:winid = v:false
   autocmd! lsp_float_preview_close CursorMoved,CursorMovedI,VimResized *
+  doautocmd User lsp_float_closed
 endfunction
 
 function! lsp#ui#vim#output#focuspreview() abort
@@ -149,18 +150,27 @@ function! s:add_float_closing_hooks() abort
     endif
 endfunction
 
+function! lsp#ui#vim#output#getpreviewwinid() abort
+    return s:winid
+endfunction
+
+function! s:open_preview(data) abort
+    if s:supports_floating && g:lsp_preview_float
+      let l:winid = lsp#ui#vim#output#floatingpreview(a:data)
+    else
+      execute &previewheight.'new'
+      let l:winid = win_getid()
+    endif
+    return l:winid
+endfunction
+
 function! lsp#ui#vim#output#preview(data) abort
     " Close any previously opened preview window
     pclose
 
     let l:current_window_id = win_getid()
 
-    if s:supports_floating && g:lsp_preview_float
-      let s:winid = lsp#ui#vim#output#floatingpreview(a:data)
-    else
-      execute &previewheight.'new'
-      let s:winid = win_getid()
-    endif
+    let s:winid = s:open_preview(a:data)
 
     let l:lines = []
     let l:ft = s:append(a:data, l:lines)
@@ -177,9 +187,12 @@ function! lsp#ui#vim#output#preview(data) abort
 
     echo ''
 
-    if s:supports_floating && s:winid && g:lsp_preview_float && has('nvim')
-      call s:adjust_float_placement(l:bufferlines, l:maxwidth)
-      call s:add_float_closing_hooks()
+    if s:supports_floating && s:winid && g:lsp_preview_float
+      if has('nvim')
+        call s:adjust_float_placement(l:bufferlines, l:maxwidth)
+        call s:add_float_closing_hooks()
+      endif
+      doautocmd User lsp_float_opened
     endif
     return ''
 endfunction

doc/vim-lsp.txt

@@ -158,11 +158,16 @@ g:lsp_preview_float                         *g:lsp_preview_float*
     Type: |Number|
     Default: `1`
 
-    If set and nvim_win_open() is available, hover information are shown in a
-    floating window as |preview-window| at the cursor position.
+    If set and nvim_win_open() or popup_create is available, hover information
+    are shown in a floating window as |preview-window| at the cursor position.
     The |preview-window| is closed automatically on cursor moves, unless it is
     focused. While focused it may be closed with <esc>.
-    This feature requires neovim 0.4.0 (current master).
+    After opening an autocmd User event lsp_float_opened is issued, as well as
+    and lsp_float_closed upon closing. This can be used to alter the preview
+    window (using lsp#ui#vim#output#getpreviewwinid() to get the window id), or
+    setup custom bindings while a preview is open.
+    This feature requires neovim 0.4.0 (current master) or
+    Vim8.1 with has('patch-8.1.1517').
 
     Example:
 	" Opens preview windows as floating
@@ -171,6 +176,11 @@ g:lsp_preview_float                         *g:lsp_preview_float*
 	" Opens preview windows as normal windows
 	let g:lsp_preview_float = 0
 
+	" Close preview window with <esc>
+	autocmd User lsp_float_opened nmap <buffer> <silent> <esc>
+		      \ <Plug>(lsp-preview-close)
+	autocmd User lsp_float_closed nunmap <buffer> <esc>
+
 g:lsp_preview_autoclose                         *g:lsp_preview_autoclose*
     Type: |Number|
     Default: `1`