patch 8.1.1560: popup window hidden option not implemented yet

Problem:    Popup window hidden option not implemented yet.
Solution:   Implement the hidden option.
diff --git a/src/popupwin.c b/src/popupwin.c
index 3603a1c..c042fe8 100644
--- a/src/popupwin.c
+++ b/src/popupwin.c
@@ -428,6 +428,13 @@
 	    semsg(_(e_invarg2), tv_get_string(&di->di_tv));
     }
 
+    nr = dict_get_number(dict, (char_u *)"hidden");
+    if (nr > 0)
+    {
+	wp->w_popup_flags |= POPF_HIDDEN;
+	--wp->w_buffer->b_nwindows;
+    }
+
     popup_mask_refresh = TRUE;
 }
 
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 3f5c9d1..7496608 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -1310,7 +1310,7 @@
   call delete('XtestNotifications')
 endfunc
 
-function Test_popup_settext()
+func Test_popup_settext()
   if !CanRunVimInTerminal()
     throw 'Skipped: cannot make screendumps'
   endif
@@ -1352,4 +1352,38 @@
   " clean up
   call StopVimInTerminal(buf)
   call delete('XtestPopupSetText')
-endfunction
+endfunc
+
+func Test_popup_hidden()
+  new
+
+  let winid = popup_atcursor('text', {'hidden': 1})
+  redraw
+  call assert_equal(0, popup_getpos(winid).visible)
+  call popup_close(winid)
+
+  let winid = popup_create('text', {'hidden': 1})
+  redraw
+  call assert_equal(0, popup_getpos(winid).visible)
+  call popup_close(winid)
+
+  func QuitCallback(id, res)
+    let s:cb_winid = a:id
+    let s:cb_res = a:res
+  endfunc
+  let winid = popup_dialog('make a choice', {'hidden': 1,
+	  \ 'filter': 'popup_filter_yesno',
+	  \ 'callback': 'QuitCallback',
+	  \ })
+  redraw
+  call assert_equal(0, popup_getpos(winid).visible)
+  exe "normal anot used by filter\<Esc>"
+  call assert_equal('not used by filter', getline(1))
+
+  call popup_show(winid)
+  call feedkeys('y', "xt")
+  call assert_equal(1, s:cb_res)
+
+  bwipe!
+  delfunc QuitCallback
+endfunc
diff --git a/src/version.c b/src/version.c
index ad09b56..ea203f6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1560,
+/**/
     1559,
 /**/
     1558,