Add nvim floating window support (replaces #3314) (#3470)

* Add nvim floating window hover support
* Add configuration for float to replace preview
* preview#ShowFloating: qualify local variables
* Configure floating preview usecases individually

Also:
  * Extract floating preview to its own file.
  * Ignore 'stay_here' option. Moving into the floating preview window
    seems confusing at best.
  * Re-use existing floating preview window if it's still up.
  * Flush out floating preview documentation.

* Watch cursor position changes per window

Floating previews open a new window, so when that window is written to,
it moves briefly there at a different position than the original window.
This makes repeated positions detected when positions are tracked at a
s: level. Instead, we change the variable to window scoped, which only
fires a message if the cursor has changed from the last position in
*that window*.

* g:ale_floating_preview cleanup
* floating_preview: add ALEDetail tests
* Fix fecs test missing runtime call
* Add ALEHover floating preview tests

Co-authored-by: Jan-Grimo Sobez <jan-grimo.sobez@phys.chem.ethz.ch>

3 files changed, 115 insertions, 7 deletions

diff --git a/autoload/ale/cursor.vim b/autoload/ale/cursor.vim
index 9ca6fb15..e8478e93 100644
--- a/autoload/ale/cursor.vim
+++ b/autoload/ale/cursor.vim
@@ -9,7 +9,6 @@ let g:ale_echo_delay = get(g:, 'ale_echo_delay', 10)
 let g:ale_echo_msg_format = get(g:, 'ale_echo_msg_format', '%code: %%s')
 
 let s:cursor_timer = -1
-let s:last_pos = [0, 0, 0]
 
 function! ale#cursor#TruncatedEcho(original_message) abort
     let l:message = a:original_message
@@ -118,14 +117,18 @@ function! ale#cursor#EchoCursorWarningWithDelay() abort
 
     let l:pos = getpos('.')[0:2]
 
+    if !exists('w:last_pos')
+        let w:last_pos = [0, 0, 0]
+    endif
+
     " Check the current buffer, line, and column number against the last
     " recorded position. If the position has actually changed, *then*
     " we should echo something. Otherwise we can end up doing processing
     " the echo message far too frequently.
-    if l:pos != s:last_pos
+    if l:pos != w:last_pos
         let l:delay = ale#Var(l:buffer, 'echo_delay')
 
-        let s:last_pos = l:pos
+        let w:last_pos = l:pos
         let s:cursor_timer = timer_start(
         \   l:delay,
         \   function('ale#cursor#EchoCursorWarning')
@@ -139,11 +142,16 @@ function! s:ShowCursorDetailForItem(loc, options) abort
     let s:last_detailed_line = line('.')
     let l:message = get(a:loc, 'detail', a:loc.text)
     let l:lines = split(l:message, "\n")
-    call ale#preview#Show(l:lines, {'stay_here': l:stay_here})
 
-    " Clear the echo message if we manually displayed details.
-    if !l:stay_here
-        execute 'echo'
+    if g:ale_floating_preview || g:ale_detail_to_floating_preview
+        call ale#floating_preview#Show(l:lines)
+    else
+        call ale#preview#Show(l:lines, {'stay_here': l:stay_here})
+
+        " Clear the echo message if we manually displayed details.
+        if !l:stay_here
+            execute 'echo'
+        endif
     endif
 endfunction
 
diff --git a/autoload/ale/floating_preview.vim b/autoload/ale/floating_preview.vim
new file mode 100644
index 00000000..e6a75689
--- /dev/null
+++ b/autoload/ale/floating_preview.vim
@@ -0,0 +1,91 @@
+" Author: Jan-Grimo Sobez <jan-grimo.sobez@phys.chem.ethz.ch>
+" Author: Kevin Clark <kevin.clark@gmail.com>
+" Description: Floating preview window for showing whatever information in.
+
+" Precondition: exists('*nvim_open_win')
+
+function! ale#floating_preview#Show(lines, ...) abort
+    if !exists('*nvim_open_win')
+        execute 'echom ''Floating windows not supported in this vim instance.'''
+
+        return
+    endif
+
+    " Remove the close autocmd so it doesn't happen mid update
+    augroup ale_floating_preview_window
+        autocmd!
+    augroup END
+
+    let l:options = get(a:000, 0, {})
+
+    " Only create a new window if we need it
+    if !exists('w:preview') || index(nvim_list_wins(), w:preview['id']) is# -1
+        call s:Create(l:options)
+    else
+        call nvim_buf_set_option(w:preview['buffer'], 'modifiable', v:true)
+    endif
+
+    " Execute commands in window context
+    let l:parent_window = nvim_get_current_win()
+
+    call nvim_set_current_win(w:preview['id'])
+
+    for l:command in get(l:options, 'commands', [])
+        call execute(l:command)
+    endfor
+
+    call nvim_set_current_win(l:parent_window)
+
+    " Return to parent context on move
+    augroup ale_floating_preview_window
+        autocmd!
+
+        if g:ale_close_preview_on_insert
+            autocmd CursorMoved,TabLeave,WinLeave,InsertEnter <buffer> ++once call s:Close()
+        else
+            autocmd CursorMoved,TabLeave,WinLeave <buffer> ++once call s:Close()
+        endif
+    augroup END
+
+    let l:width = max(map(copy(a:lines), 'strdisplaywidth(v:val)'))
+    let l:height = min([len(a:lines), 10])
+    call nvim_win_set_width(w:preview['id'], l:width)
+    call nvim_win_set_height(w:preview['id'], l:height)
+
+    call nvim_buf_set_lines(w:preview['buffer'], 0, -1, v:false, a:lines)
+    call nvim_buf_set_option(w:preview['buffer'], 'modified', v:false)
+    call nvim_buf_set_option(w:preview['buffer'], 'modifiable', v:false)
+endfunction
+
+function! s:Create(options) abort
+    let l:buffer = nvim_create_buf(v:false, v:false)
+    let l:winid = nvim_open_win(l:buffer, v:false, {
+    \ 'relative': 'cursor',
+    \ 'row': 1,
+    \ 'col': 0,
+    \ 'width': 42,
+    \ 'height': 4,
+    \ 'style': 'minimal'
+    \ })
+    call nvim_buf_set_option(l:buffer, 'buftype', 'acwrite')
+    call nvim_buf_set_option(l:buffer, 'bufhidden', 'delete')
+    call nvim_buf_set_option(l:buffer, 'swapfile', v:false)
+    call nvim_buf_set_option(l:buffer, 'filetype', get(a:options, 'filetype', 'ale-preview'))
+
+    let w:preview = {'id': l:winid, 'buffer': l:buffer}
+endfunction
+
+function! s:Close() abort
+    if !exists('w:preview')
+        return
+    endif
+
+    call setbufvar(w:preview['buffer'], '&modified', 0)
+
+    if win_id2win(w:preview['id']) > 0
+        execute win_id2win(w:preview['id']).'wincmd c'
+    endif
+
+    unlet w:preview
+endfunction
+
diff --git a/autoload/ale/hover.vim b/autoload/ale/hover.vim
index 1d38f3b9..cb0379fd 100644
--- a/autoload/ale/hover.vim
+++ b/autoload/ale/hover.vim
@@ -46,6 +46,10 @@ function! ale#hover#HandleTSServerResponse(conn_id, response) abort
                 call balloon_show(a:response.body.displayString)
             elseif get(l:options, 'truncated_echo', 0)
                 call ale#cursor#TruncatedEcho(split(a:response.body.displayString, "\n")[0])
+            elseif g:ale_hover_to_floating_preview || g:ale_floating_preview
+                call ale#floating_preview#Show(split(a:response.body.displayString, "\n"), {
+                \   'filetype': 'ale-preview.message',
+                \})
             elseif g:ale_hover_to_preview
                 call ale#preview#Show(split(a:response.body.displayString, "\n"), {
                 \   'filetype': 'ale-preview.message',
@@ -226,6 +230,11 @@ function! ale#hover#HandleLSPResponse(conn_id, response) abort
                 call balloon_show(join(l:lines, "\n"))
             elseif get(l:options, 'truncated_echo', 0)
                 call ale#cursor#TruncatedEcho(l:lines[0])
+            elseif g:ale_hover_to_floating_preview || g:ale_floating_preview
+                call ale#floating_preview#Show(l:lines, {
+                \   'filetype': 'ale-preview.message',
+                \   'commands': l:commands,
+                \})
             elseif g:ale_hover_to_preview
                 call ale#preview#Show(l:lines, {
                 \   'filetype': 'ale-preview.message',