Support Vim's popup windows for hunk previews.

Note this prevents staging partial hunks via the previw window.

README.mkd

@@ -200,6 +200,8 @@ To stage part of any hunk:
 * delete the lines you do not want to stage;
 * stage the remaining lines: either write (`:w`) the window or stage via `<Leader>hs` or `:GitGutterStageHunk`.
 
+Note the above workflow is not possible if you have opted in to preview hunks with Vim's popup windows.
+
 See the FAQ if you want to unstage staged changes.
 
 The `.` command will work with both these if you install [repeat.vim](https://github.com/tpope/vim-repeat).
@@ -269,7 +271,7 @@ You can customise:
 * Whether vim-gitgutter runs asynchronously (defaults to yes)
 * Whether to clobber or preserve non-gitgutter signs
 * The priority of gitgutter's signs.
-* Whether to use a floating window for hunk previews (Neovim only)
+* Whether to use a floating/popup window for hunk previews
 
 Please note that vim-gitgutter won't override any colours or highlights you've set in your colorscheme.
 
@@ -455,9 +457,9 @@ let g:gitgutter_async = 0
 ```
 
 
-#### To use floating windows for hunk previews
+#### To use floating/popup windows for hunk previews
 
-Add `let g:gitgutter_preview_win_floating = 1` to your vimrc.  This only takes effect on Neovim.
+Add `let g:gitgutter_preview_win_floating = 1` to your vimrc.  Note that on Vim this prevents you staging (partial) hunks via the preview window.
 
 
 ### Extensions

autoload/gitgutter/hunk.vim

@@ -389,27 +389,42 @@ endfunction
 " Preview window: moves cursor to preview window.
 function! s:open_hunk_preview_window()
   if g:gitgutter_preview_win_floating
-    call s:close_hunk_preview_window()
+    if exists('*nvim_open_win')
+      call s:close_hunk_preview_window()
 
-    let buf = nvim_create_buf(v:false, v:false)
-    " Set default width and height for now.
-    let s:winid = nvim_open_win(buf, v:false, {
-          \ 'relative': 'cursor',
-          \ 'row': 1,
-          \ 'col': 0,
-          \ 'width': 42,
-          \ 'height': &previewheight,
-          \ 'style': 'minimal'
-          \ })
-    call nvim_buf_set_option(buf, 'filetype',  'diff')
-    call nvim_buf_set_option(buf, 'buftype',   'nofile')
-    call nvim_buf_set_option(buf, 'bufhidden', 'delete')
-    call nvim_buf_set_option(buf, 'swapfile',  v:false)
+      let buf = nvim_create_buf(v:false, v:false)
+      " Set default width and height for now.
+      let s:winid = nvim_open_win(buf, v:false, {
+            \ 'relative': 'cursor',
+            \ 'row': 1,
+            \ 'col': 0,
+            \ 'width': 42,
+            \ 'height': &previewheight,
+            \ 'style': 'minimal'
+            \ })
+      call nvim_buf_set_option(buf, 'filetype',  'diff')
+      call nvim_buf_set_option(buf, 'buftype',   'nofile')
+      call nvim_buf_set_option(buf, 'bufhidden', 'delete')
+      call nvim_buf_set_option(buf, 'swapfile',  v:false)
 
-    " Assumes cursor is in original window.
-    autocmd CursorMoved <buffer> ++once call s:close_hunk_preview_window()
+      " Assumes cursor is in original window.
+      autocmd CursorMoved <buffer> ++once call s:close_hunk_preview_window()
 
-    return
+      return
+    endif
+
+    if exists('*popup_create')
+      let s:winid = popup_create('', {
+            \ 'line': 'cursor+1',
+            \ 'col': 'cursor',
+            \ 'moved': 'any',
+            \ })
+
+      call setbufvar(winbufnr(s:winid), '&filetype', 'diff')
+      call win_execute(s:winid, 'syntax enable')
+
+      return
+    endif
   endif
 
   silent! wincmd P
@@ -430,16 +445,22 @@ function! s:populate_hunk_preview_window(header, body)
   let height = min([body_length, &previewheight])
 
   if g:gitgutter_preview_win_floating
-    " Assumes cursor is not in previewing window.
-    call nvim_buf_set_var(winbufnr(s:winid), 'hunk_header', a:header)
+    if exists('*nvim_open_win')
+      " Assumes cursor is not in previewing window.
+      call nvim_buf_set_var(winbufnr(s:winid), 'hunk_header', a:header)
 
-    let width = max(map(copy(a:body), 'strdisplaywidth(v:val)'))
-    call nvim_win_set_width(s:winid, width)
-    call nvim_win_set_height(s:winid, height)
+      let width = max(map(copy(a:body), 'strdisplaywidth(v:val)'))
+      call nvim_win_set_width(s:winid, width)
+      call nvim_win_set_height(s:winid, height)
 
-    call nvim_buf_set_lines( winbufnr(s:winid), 0, -1, v:false, [])
-    call nvim_buf_set_lines( winbufnr(s:winid), 0, -1, v:false, a:body)
-    call nvim_win_set_cursor( s:winid, [1,0])
+      call nvim_buf_set_lines( winbufnr(s:winid), 0, -1, v:false, [])
+      call nvim_buf_set_lines( winbufnr(s:winid), 0, -1, v:false, a:body)
+      call nvim_win_set_cursor( s:winid, [1,0])
+    endif
+
+    if exists('*popup_create')
+      call popup_settext(s:winid, a:body)
+    endif
 
   else
     let b:hunk_header = a:header

doc/gitgutter.txt

@@ -438,11 +438,13 @@ it in your |vimrc|:
 
 
                                              *g:gitgutter_preview_win_floating*
-Default: 1 (Neovim)
-         0 (Vim)
+Default: 0 (Vim)
+         0 (NeoVim which does not support floating windows)
+         1 (NeoVim which does support floating windows)
 
-Whether to use floating windows for hunk previews.  Only takes effect on
-Neovim.
+Whether to use floating/popup windows for hunk previews.  Note that if you use
+popup windows on Vim you will not be able to stage partial hunks via the
+preview window.
 
                                            *g:gitgutter_terminal_reports_focus*
 Default: 1