patch 8.1.1875: cannot get size and position of the popup menu

Problem:    Cannot get size and position of the popup menu.
Solution:   Add pum_getpos(). (Ben Jackson, closes #4827)
diff --git a/runtime/doc/autocmd.txt b/runtime/doc/autocmd.txt
index 0cab9d8..7893651 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -595,6 +595,10 @@
 				    scrollbar		TRUE if visible
 
 				It is not allowed to change the text |textlock|.
+
+				The size and position of the popup are also
+				available by calling |pum_getpos()|.
+
 							*CompleteDone*
 CompleteDone			After Insert mode completion is done.  Either
 				when something was completed or abandoning
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 4bc4287..1e5b5a0 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -2613,6 +2613,7 @@
 prop_type_get([{name} [, {props}])
 				Dict	get property type values
 prop_type_list([{props}])	List	get list of property types
+pum_getpos()			Dict	position and size of pum if visible
 pumvisible()			Number	whether popup menu is visible
 pyeval({expr})			any	evaluate |Python| expression
 py3eval({expr})			any	evaluate |python3| expression
@@ -3477,6 +3478,10 @@
 		the items listed in {what} are returned.  Unsupported items in
 		{what} are silently ignored.
 
+		To get the position and size of the popup menu, see
+		|pum_getpos()|. It's also available in |v:event| during the
+		|CompleteChanged| event.
+
 		Examples: >
 			" Get all items
 			call complete_info()
@@ -6977,6 +6982,20 @@
 <
 prop_ functions are documented here: |text-prop-functions|.
 
+pum_getpos()						*pum_getpos()*
+		If the popup menu (see |ins-completion-menu|) is not visible,
+		returns an empty |Dictionary|, otherwise, returns a
+		|Dictionary| with the following keys:
+			height		nr of items visible
+			width		screen cells
+			row		top screen row (0 first row)
+			col		leftmost screen column (0 first col)
+			size		total nr of items
+			scrollbar	|TRUE| if visible
+
+		The values are the same as in |v:event| during
+		|CompleteChanged|.
+
 pumvisible()						*pumvisible()*
 		Returns non-zero when the popup menu is visible, zero
 		otherwise.  See |ins-completion-menu|.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index f117563..8943093 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -234,6 +234,7 @@
 #endif
 static void f_prevnonblank(typval_T *argvars, typval_T *rettv);
 static void f_printf(typval_T *argvars, typval_T *rettv);
+static void f_pum_getpos(typval_T *argvars, typval_T *rettv);
 static void f_pumvisible(typval_T *argvars, typval_T *rettv);
 #ifdef FEAT_PYTHON3
 static void f_py3eval(typval_T *argvars, typval_T *rettv);
@@ -741,6 +742,7 @@
     {"prop_type_get",	1, 2, 0,	  f_prop_type_get},
     {"prop_type_list",	0, 1, 0,	  f_prop_type_list},
 #endif
+    {"pum_getpos",	0, 0, 0,	  f_pum_getpos},
     {"pumvisible",	0, 0, 0,	  f_pumvisible},
 #ifdef FEAT_PYTHON3
     {"py3eval",		1, 1, 0,	  f_py3eval},
@@ -7961,6 +7963,19 @@
 }
 
 /*
+ * "pum_getpos()" function
+ */
+    static void
+f_pum_getpos(typval_T *argvars UNUSED, typval_T *rettv UNUSED)
+{
+    if (rettv_dict_alloc(rettv) != OK)
+	return;
+#ifdef FEAT_INS_EXPAND
+    pum_set_event_info(rettv->vval.v_dict);
+#endif
+}
+
+/*
  * "pumvisible()" function
  */
     static void
diff --git a/src/testdir/test_popup.vim b/src/testdir/test_popup.vim
index e7b4c72..d9f561b 100644
--- a/src/testdir/test_popup.vim
+++ b/src/testdir/test_popup.vim
@@ -1033,6 +1033,20 @@
   bwipe!
 endfunc
 
+func Test_popup_complete_info_no_pum()
+  new
+  call assert_false( pumvisible() )
+  let no_pum_info = complete_info()
+  let d = {
+        \   'mode': '',
+        \   'pum_visible': 0,
+        \   'items': [],
+        \   'selected': -1,
+        \  }
+  call assert_equal( d, complete_info() )
+  bwipe!
+endfunc
+
 func Test_CompleteChanged()
   new
   call setline(1, ['foo', 'bar', 'foobar', ''])
@@ -1063,8 +1077,36 @@
 
   autocmd! AAAAA_Group
   set complete& completeopt&
-  delfunc! OnPumchange
+  delfunc! OnPumChange
   bw!
 endfunc
 
+function! GetPumPosition()
+  call assert_true( pumvisible() )
+  let g:pum_pos = pum_getpos()
+  return ''
+endfunction
+
+func Test_pum_getpos()
+  new
+  inoremap <buffer><F5> <C-R>=GetPumPosition()<CR>
+  setlocal completefunc=UserDefinedComplete
+
+  let d = {
+    \   'height':    5,
+    \   'width':     15,
+    \   'row':       1,
+    \   'col':       0,
+    \   'size':      5,
+    \   'scrollbar': v:false,
+    \ }
+  call feedkeys("i\<C-X>\<C-U>\<F5>", 'tx')
+  call assert_equal(d, g:pum_pos)
+
+  call assert_false( pumvisible() )
+  call assert_equal( {}, pum_getpos() )
+  bw!
+  unlet g:pum_pos
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 8753421..2c02209 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1875,
+/**/
     1874,
 /**/
     1873,