vim-patch:8.2.3193: screenpos() is wrong when 'display' is "lastline"

Problem:    screenpos() is wrong when the last line is partially visible and
            'display' is "lastline".
Solution:   Also compute the position for a partially visible line.
            (closes vim/vim#8599)

https://github.com/vim/vim/commit/189663bdac1156237c49925f77bd197c1bdea12c

Co-authored-by: Bram Moolenaar <Bram@vim.org>

2 files changed, 32 insertions, 16 deletions

diff --git a/src/nvim/move.c b/src/nvim/move.c
index 1d2a3a2276..05795bf858 100644
--- a/src/nvim/move.c
+++ b/src/nvim/move.c
@@ -921,7 +921,7 @@ void textpos2screenpos(win_T *wp, pos_T *pos, int *rowp, int *scolp, int *ccolp,
   colnr_T coloff = 0;
   bool visible_row = false;
 
-  if (pos->lnum >= wp->w_topline && pos->lnum < wp->w_botline) {
+  if (pos->lnum >= wp->w_topline && pos->lnum <= wp->w_botline) {
     row = plines_m_win(wp, wp->w_topline, pos->lnum - 1) + 1;
     visible_row = true;
   } else if (pos->lnum < wp->w_topline) {
@@ -955,15 +955,15 @@ void textpos2screenpos(win_T *wp, pos_T *pos, int *rowp, int *scolp, int *ccolp,
 
     col -= wp->w_leftcol;
 
-    if (col >= 0 && col < wp->w_width) {
+    if (col >= 0 && col < wp->w_width && row + rowoff <= wp->w_height) {
       coloff = col - scol + (local ? 0 : wp->w_wincol + wp->w_wincol_off) + 1;
     } else {
+      // character is left, right or below of the window
       scol = ccol = ecol = 0;
-      // character is left or right of the window
       if (local) {
         coloff = col < 0 ? -1 : wp->w_width_inner + 1;
       } else {
-        row = 0;
+        row = rowoff = 0;
       }
     }
   }
diff --git a/src/nvim/testdir/test_cursor_func.vim b/src/nvim/testdir/test_cursor_func.vim
index 7f9e74e94b..0a88bf9db3 100644
--- a/src/nvim/testdir/test_cursor_func.vim
+++ b/src/nvim/testdir/test_cursor_func.vim
@@ -82,25 +82,41 @@ func Test_screenpos()
   let winid = win_getid()
   let [winrow, wincol] = win_screenpos(winid)
   call assert_equal({'row': winrow,
-    \ 'col': wincol + 0,
-    \ 'curscol': wincol + 7,
-    \ 'endcol': wincol + 7}, winid->screenpos(1, 1))
+	\ 'col': wincol + 0,
+	\ 'curscol': wincol + 7,
+	\ 'endcol': wincol + 7}, winid->screenpos(1, 1))
   call assert_equal({'row': winrow,
-    \ 'col': wincol + 13,
-    \ 'curscol': wincol + 13,
-    \ 'endcol': wincol + 13}, winid->screenpos(1, 7))
+	\ 'col': wincol + 13,
+	\ 'curscol': wincol + 13,
+	\ 'endcol': wincol + 13}, winid->screenpos(1, 7))
   call assert_equal({'row': winrow + 2,
-    \ 'col': wincol + 1,
-    \ 'curscol': wincol + 1,
-    \ 'endcol': wincol + 1}, screenpos(winid, 2, 22))
+	\ 'col': wincol + 1,
+	\ 'curscol': wincol + 1,
+	\ 'endcol': wincol + 1}, screenpos(winid, 2, 22))
   setlocal number
   call assert_equal({'row': winrow + 3,
-    \ 'col': wincol + 9,
-    \ 'curscol': wincol + 9,
-    \ 'endcol': wincol + 9}, screenpos(winid, 2, 22))
+	\ 'col': wincol + 9,
+	\ 'curscol': wincol + 9,
+	\ 'endcol': wincol + 9}, screenpos(winid, 2, 22))
+
+  let wininfo = getwininfo(winid)[0]
+  call setline(3, ['x']->repeat(wininfo.height))
+  call setline(line('$') + 1, 'x'->repeat(wininfo.width * 3))
+  setlocal nonumber display=lastline so=0
+  exe "normal G\<C-Y>\<C-Y>"
+  redraw
+  call assert_equal({'row': winrow + wininfo.height - 1,
+	\ 'col': wincol + 7,
+	\ 'curscol': wincol + 7,
+	\ 'endcol': wincol + 7}, winid->screenpos(line('$'), 8))
+  call assert_equal({'row': winrow - 1, 'col': 0, 'curscol': 0, 'endcol': 0},
+        \ winid->screenpos(line('$'), 22))
+
   close
   call assert_equal({}, screenpos(999, 1, 1))
+
   bwipe!
+  set display&
 
   call assert_equal({'col': 1, 'row': 1, 'endcol': 1, 'curscol': 1}, screenpos(win_getid(), 1, 1))
   " nmenu WinBar.TEST :