patch 8.2.3614: zindex of popup windows not used when redrawing popup menu

Problem:    zindex of popup windows not used when redrawing popup menu.
Solution:   Check the zindex when redrawing the popup menu.  (closes #9129,
            closes #9089)
diff --git a/src/testdir/dumps/Test_popupwin_popupmenu_masking_1.dump b/src/testdir/dumps/Test_popupwin_popupmenu_masking_1.dump
new file mode 100644
index 0000000..9cf4149
--- /dev/null
+++ b/src/testdir/dumps/Test_popupwin_popupmenu_masking_1.dump
@@ -0,0 +1,14 @@
+|t+0&#ffffff0|e|x|t| |t|e|x|t| |t|e|x|t| |t|e|x|t| |t|e|x|t| |t|a|w|o|r|d> @2|p+0#ffffff16#e000002|o|p|u|p| |b|e|l|o|w| @1|╔+0#0000001#e0e0e08|═@15|X| +0#0000000#ffffff0@9
+|~+0#4040ff13&| @23| +0#0000001#e0e0e08|w|r|d| @4|W| |e|x|t|r|a| |t|e|x|t| |║| |w|o|r|d|s| |a|r|e| |c|o@1|l| |║| +0#4040ff13#ffffff0@9
+|~| @23| +0#0000001#ffd7ff255|a|n|o|t|w|r|d| |W| |e|x|t|r|a| |t|e|x|t| |╚+0&#e0e0e08|═@15|⇲| +0#4040ff13#ffffff0@9
+|~| @19|p+0#0000000#ffff4012|o|p|u|p| |o|n| |t|o|p| +0#0000001#ffd7ff255|W| |e|x|t|r|a| |t|e|x|t| | +0#ffffff16#e000002@3| +0#4040ff13#ffffff0@23
+|~| @19|p+0#0000000#ffff4012|o|p|u|p| |o|n| |t|o|p| +0#0000001#ffd7ff255|W| |e|x|t|r|a| |t|e|x|t| | +0#4040ff13#ffffff0@27
+|~| @19|p+0#0000000#ffff4012|o|p|u|p| |o|n| |t|o|p| +0#4040ff13#ffffff0@41
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|-+2#0000000&@1| |U|s|e|r| |d|e|f|i|n|e|d| |c|o|m|p|l|e|t|i|o|n| |(|^|U|^|N|^|P|)| |m+0#00e0003&|a|t|c|h| |1| |o|f| |4| +0#0000000&@26
diff --git a/src/testdir/dumps/Test_popupwin_popupmenu_masking_2.dump b/src/testdir/dumps/Test_popupwin_popupmenu_masking_2.dump
new file mode 100644
index 0000000..41fb879
--- /dev/null
+++ b/src/testdir/dumps/Test_popupwin_popupmenu_masking_2.dump
@@ -0,0 +1,14 @@
+|t+0&#ffffff0|e|x|t| |t|e|x|t| |t|e|x|t| |t|e|x|t| |t|e|x|t| |t|a|w|o|r>d| @2|p+0#ffffff16#e000002|o|p|u|p| |b|e|l|o|w| @5| +0#0000000#ffffff0@23
+|~+0#4040ff13&| @32|p+0#ffffff16#e000002|o|p|u|p| |b|e|l|o|w| @5| +0#4040ff13#ffffff0@23
+|~| @32|p+0#ffffff16#e000002|o|p|u|p| |b|e|l|o|w| @5| +0#4040ff13#ffffff0@23
+|~| @19|p+0#0000000#ffff4012|o|p|u|p| |o|n| |t|o|p| +0#4040ff13#ffffff0|p+0#ffffff16#e000002|o|p|u|p| |b|e|l|o|w| @5| +0#4040ff13#ffffff0@23
+|~| @19|p+0#0000000#ffff4012|o|p|u|p| |o|n| |t|o|p| +0#4040ff13#ffffff0@41
+|~| @19|p+0#0000000#ffff4012|o|p|u|p| |o|n| |t|o|p| +0#4040ff13#ffffff0@41
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+| +0#0000000&@56|1|,|3|1| @9|A|l@1| 
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 83d632e..15fa3ca 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -3328,6 +3328,32 @@
 	endif
       endfunc
 
+      func OpenOtherPopups()
+	call popup_create([
+		\ 'popup below',
+		\ 'popup below',
+		\ 'popup below',
+		\ 'popup below',
+	      \ ], #{
+		\ line: 'cursor',
+		\ col: 'cursor+3',
+		\ highlight: 'ErrorMsg',
+		\ minwidth: 17,
+		\ zindex: 50,
+	      \ })
+	call popup_create([
+		\ 'popup on top',
+		\ 'popup on top',
+		\ 'popup on top',
+	      \ ], #{
+		\ line: 'cursor+3',
+		\ col: 'cursor-10',
+		\ highlight: 'Search',
+		\ minwidth: 10,
+		\ zindex: 200,
+	      \ })
+      endfunc
+
       " Check that no autocommands are triggered for the info popup
       au WinEnter * if win_gettype() == 'popup' | call setline(2, 'WinEnter') | endif
       au WinLeave * if win_gettype() == 'popup' | call setline(2, 'WinLeave') | endif
@@ -3520,6 +3546,29 @@
   call delete('XtestInfoPopupWide')
 endfunc
 
+func Test_popupmenu_masking()
+  " Test that popup windows that are opened while popup menu is open are
+  " properly displayed.
+  CheckScreendump
+  CheckFeature quickfix
+
+  let lines = Get_popupmenu_lines()
+  call add(lines, 'inoremap <C-A> <Cmd>call OpenOtherPopups()<CR>')
+  call writefile(lines, 'XtestPopupmenuMasking')
+
+  let buf = RunVimInTerminal('-S XtestPopupmenuMasking', #{rows: 14})
+  call TermWait(buf, 25)
+
+  call term_sendkeys(buf, "A\<C-X>\<C-U>\<C-A>")
+  call VerifyScreenDump(buf, 'Test_popupwin_popupmenu_masking_1', {})
+
+  call term_sendkeys(buf, "\<Esc>")
+  call VerifyScreenDump(buf, 'Test_popupwin_popupmenu_masking_2', {})
+
+  call StopVimInTerminal(buf)
+  call delete('XtestPopupmenuMasking')
+endfunc
+
 func Test_popupwin_recycle_bnr()
   let bufnr = popup_notification('nothing wrong', {})->winbufnr()
   call popup_clear()