Nvim: make :SignifyPreviewHunk use floating window (#302)

autoload/sy/repo.vim

@@ -306,16 +306,20 @@ function! s:preview_hunk(_sy, vcs, diff) abort
     return
   endif
 
-  silent! wincmd P
-  if !&previewwindow
-    noautocmd botright new
+  if exists('*nvim_open_win')
+    call sy#util#renderPopup(hunk)
+  else
+    silent! wincmd P
+    if !&previewwindow
+      noautocmd botright new
+    endif
+    call setline(1, hunk)
+    silent! %foldopen!
+    setlocal previewwindow filetype=diff buftype=nofile bufhidden=delete
+    " With :noautocmd wincmd p, the first line of the preview window would show
+    " the 'cursorline', although it's not focused. Use feedkeys() instead.
+    noautocmd call feedkeys("\<c-w>p", 'nt')
   endif
-  call setline(1, hunk)
-  silent! %foldopen!
-  setlocal previewwindow filetype=diff buftype=nofile bufhidden=delete
-  " With :noautocmd wincmd p, the first line of the preview window would show
-  " the 'cursorline', although it's not focused. Use feedkeys() instead.
-  noautocmd call feedkeys("\<c-w>p", 'nt')
 endfunction
 
 function! s:is_cur_line_in_hunk(hunkline) abort

autoload/sy/util.vim

@@ -107,3 +107,42 @@ function! sy#util#execute(cmd) abort
   silent! execute 'language message' lang
   return output
 endfunction
+
+let s:window = 0
+
+function! sy#util#closePopup()
+  if s:window
+    let id = win_id2win(s:window)
+    if id > 0
+      execute id . 'close!'
+    endif
+    let s:window = 0
+  endif
+endfunction
+
+function! sy#util#renderPopup(input, ...)
+  call sy#util#closePopup()
+  let s:buf = nvim_create_buf(0, 1)
+  call nvim_buf_set_option(s:buf, 'syntax', 'diff')
+  let max_width = 100
+  let max_height = 16
+  let width = max(map(copy(a:input), {_, v -> len(v)})) + 1
+  let width = (width > max_width) ? max_width : width
+  let height = len(a:input)
+  let height = (height > max_height) ? max_height : height
+  call nvim_buf_set_lines(s:buf, 0, -1, 0, a:input)
+  let s:window = call('nvim_open_win', [s:buf, v:false, {
+          \ 'relative': 'cursor',
+          \ 'row': 0,
+          \ 'col': 0,
+          \   'width': width,
+          \   'height': height,
+          \ }])
+  call nvim_win_set_option(s:window, 'cursorline', v:false)
+  call nvim_win_set_option(s:window, 'foldenable', v:false)
+  call nvim_win_set_option(s:window, 'number', v:false)
+  call nvim_win_set_option(s:window, 'relativenumber', v:false)
+  call nvim_win_set_option(s:window, 'statusline', '')
+  call nvim_win_set_option(s:window, 'wrap', v:true)
+  autocmd CursorMoved * call sy#util#closePopup()
+endfunction