Add g:which_key_floating_opts_explicit and g:which_key_floating_vars

autoload/which_key/window.vim

@@ -57,10 +57,19 @@ endfunction
 
 function! s:show_popup(rows) abort
   if !exists('s:popup_id')
-    let s:popup_id = popup_create([], {'highlight': 'WhichKeyFloating'})
+    let opts = {
+      \ 'highlight': 'WhichKeyFloating',
+      \ }
+    let opts = s:apply_custom_floating_opts(opts)
+    let s:popup_id = popup_create([], opts)
     call popup_hide(s:popup_id)
     call setbufvar(winbufnr(s:popup_id), '&filetype', 'which_key')
     call win_execute(s:popup_id, 'setlocal nonumber nowrap')
+    if exists('g:which_key_floating_vars')
+      for [key, val] in items(g:which_key_floating_vars)
+        call setwinvar(s:popup_id, key, val)
+      endfor
+    endif
   endif
 
   let rows = s:append_prompt(a:rows)
@@ -91,6 +100,11 @@ function! s:apply_custom_floating_opts(opts) abort
       endif
     endfor
   endif
+  if exists('g:which_key_floating_opts_explicit')
+    for [key, val] in items(g:which_key_floating_opts_explicit)
+      let opts[key] = val
+    endfor
+  endif
   return opts
 endfunction
 
@@ -135,6 +149,11 @@ function! s:show_floating_win(rows, layout) abort
     call s:hide_cursor()
     call setbufvar(s:bufnr, '&ft', 'which_key')
     call setwinvar(s:floating_winid, '&winhl', 'Normal:WhichKeyFloating')
+    if exists('g:which_key_floating_vars')
+      for [key, val] in items(g:which_key_floating_vars)
+        call setwinvar(s:floating_winid, key, val)
+      endfor
+    endif
   else
     call nvim_win_set_config(s:floating_winid, opts)
   endif

doc/vim-which-key.txt

@@ -244,6 +244,22 @@ or `-[number]` which means plus or minus `numberl` based on the default value
 caculated by vim-which-key.
 >
  let g:which_key_floating_opts = { 'row': '-1' }
+<
+                                          *g:which_key_floating_opts_explicit*
+Type: |Dict|
+Default: `Undefined`
+
+You can use this option to pass explicit {options} to |popup_create| or |nvim_open_win|. For example to change the borders:
+>
+ let g:which_key_floating_opts_explicit = { 'border': 'shadow' }
+<
+                                                   *g:which_key_floating_vars*
+Type: |Dict|
+Default: `Undefined`
+
+You can use this option to set variables on the floating window. For example to make the window transparent (Neovim only):
+>
+ let g:which_key_floating_vars = { '&winblend': '30' }
 <
                                                 *g:which_key_run_map_on_popup*
 Type: |Number|