patch 8.1.2210: using negative offset for popup_create() does not work

Problem:    Using negative offset for popup_create() does not work.
Solution:   Use -1 instead of zero. (closes #5111)
diff --git a/src/testdir/dumps/Test_popupwin_corners.dump b/src/testdir/dumps/Test_popupwin_corners.dump
index eee6601..82188c0 100644
--- a/src/testdir/dumps/Test_popupwin_corners.dump
+++ b/src/testdir/dumps/Test_popupwin_corners.dump
@@ -1,12 +1,12 @@
-|-+0&#ffffff0@59| @14
-|-@1|#|-@20|@|-@34| @14
-|-@1|╔+0#0000001#ffd7ff255|═@7|╗|-+0#0000000#ffffff0@2|╔+0#0000001#ffd7ff255|═@7|╗|-+0#0000000#ffffff0@2|╔+0#0000001#ffd7ff255|═@7|╗|-+0#0000000#ffffff0@2|╔+0#0000001#ffd7ff255|═@7|╗|-+0#0000000#ffffff0@8| @14
-|-@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@8| @14
-|-@1|║+0#0000001#ffd7ff255| |f|i|r|s|t| @1|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| |F|i|r|s|t| @1|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| |f|i|R|S|t| @1|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| |F|I|r|s|T| @1|║|-+0#0000000#ffffff0@8| @14
-|-@1|║+0#0000001#ffd7ff255| |s|e|c|o|n|d| |║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| |S|e|c|o|n|D| |║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| |s|e|C|O|n|d| |║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| |S|E|c|o|N|D| |║|-+0#0000000#ffffff0@8| @14
-|-@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@2|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@8| @14
-|-@1|╚+0#0000001#ffd7ff255|═@7|╝|-+0#0000000#ffffff0@2|╚+0#0000001#ffd7ff255|═@7|╝|-+0#0000000#ffffff0@2|╚+0#0000001#ffd7ff255|═@7|╝|-+0#0000000#ffffff0@2|╚+0#0000001#ffd7ff255|═@7|╝|-+0#0000000#ffffff0@8| @14
-|-@27|%|-@20>&|-@8| @14
+|-+0&#ffffff0@49>*|-@8| @14
+|-@1|#|-@19|@|-@25|╔+0#0000001#ffd7ff255|═@4|╗|-+0#0000000#ffffff0@2| @14
+|-@1|╔+0#0000001#ffd7ff255|═@7|╗|-+0#0000000#ffffff0@1|╔+0#0000001#ffd7ff255|═@7|╗|-+0#0000000#ffffff0@1|╔+0#0000001#ffd7ff255|═@7|╗|-+0#0000000#ffffff0@1|╔+0#0000001#ffd7ff255|═@7|╗|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| @4|║|-+0#0000000#ffffff0@2| @14
+|-@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| |o|n|e| |║|-+0#0000000#ffffff0@2| @14
+|-@1|║+0#0000001#ffd7ff255| |f|i|r|s|t| @1|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| |F|i|r|s|t| @1|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| |f|i|R|S|t| @1|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| |F|I|r|s|T| @1|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| |t|w|o| |║|-+0#0000000#ffffff0@2| @14
+|-@1|║+0#0000001#ffd7ff255| |s|e|c|o|n|d| |║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| |S|e|c|o|n|D| |║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| |s|e|C|O|n|d| |║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| |S|E|c|o|N|D| |║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| @4|║|-+0#0000000#ffffff0@2| @14
+|-@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@1|║+0#0000001#ffd7ff255| @7|║|-+0#0000000#ffffff0@1|╚+0#0000001#ffd7ff255|═@4|╝|-+0#0000000#ffffff0@2| @14
+|-@1|╚+0#0000001#ffd7ff255|═@7|╝|-+0#0000000#ffffff0@1|╚+0#0000001#ffd7ff255|═@7|╝|-+0#0000000#ffffff0@1|╚+0#0000001#ffd7ff255|═@7|╝|-+0#0000000#ffffff0@1|╚+0#0000001#ffd7ff255|═@7|╝|-+0#0000000#ffffff0@11| @14
+|-@25|%|-@19|&|-@11| @14
 |-@59| @14
 |-@59| @14
-@57|9|,|5|1| @9|T|o|p| 
+@57|1|,|5|1| @9|T|o|p| 
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index dc382d8..1c5bcb2 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -278,7 +278,7 @@
 	      \ border: [],
 	      \ padding: [],
 	      \ })
-	normal 25|r@
+	normal 24|r@
 	let winid1 = popup_create(['First', 'SeconD'], #{
 	      \ line: 'cursor+1',
 	      \ col: 'cursor',
@@ -286,7 +286,7 @@
 	      \ border: [],
 	      \ padding: [],
 	      \ })
-	normal 9G29|r%
+	normal 9G27|r%
 	let winid1 = popup_create(['fiRSt', 'seCOnd'], #{
 	      \ line: 'cursor-1',
 	      \ col: 'cursor',
@@ -294,7 +294,7 @@
 	      \ border: [],
 	      \ padding: [],
 	      \ })
-	normal 51|r&
+	normal 48|r&
 	let winid1 = popup_create(['FIrsT', 'SEcoND'], #{
 	      \ line: 'cursor-1',
 	      \ col: 'cursor',
@@ -302,6 +302,14 @@
 	      \ border: [],
 	      \ padding: [],
 	      \ })
+	normal 1G51|r*
+	let winid1 = popup_create(['one', 'two'], #{
+	      \ line: 'cursor-1',
+	      \ col: 'cursor',
+	      \ pos: 'botleft',
+	      \ border: [],
+	      \ padding: [],
+	      \ })
   END
   call writefile(lines, 'XtestPopupCorners')
   let buf = RunVimInTerminal('-S XtestPopupCorners', #{rows: 12})