vim-patch:8.2.4568: getmousepos() does not compute the column below the last line

Problem:    getmousepos() does not compute the column below the last line.
Solution:   Also compute the column when the mouse is below the last line.
            (Sean Dewar, closes vim/vim#9946)
10792feebd

test_setmouse is N/A.

src/nvim/eval/funcs.c

@@ -3753,9 +3753,8 @@ static void f_getmousepos(typval_T *argvars, typval_T *rettv, FunPtr fptr)
       winrow = row + 1 + wp->w_border_adj[0];  // Adjust by 1 for top border
       wincol = col + 1 + wp->w_border_adj[3];  // Adjust by 1 for left border
       if (row >= 0 && row < wp->w_height && col >= 0 && col < wp->w_width) {
-        if (!mouse_comp_pos(wp, &row, &col, &lnum)) {
+        (void)mouse_comp_pos(wp, &row, &col, &lnum);
-          col = vcol2col(wp, lnum, col);
+        col = vcol2col(wp, lnum, col);
-        }
         column = col + 1;
       }
     }

src/nvim/testdir/test_functions.vim

@@ -1801,6 +1801,33 @@ func Test_getmousepos()
         \ line: 1,
         \ column: 8,
         \ }, getmousepos())
+
+  " If the mouse is positioned past the last buffer line, "line" and "column"
+  " should act like it's positioned on the last buffer line.
+  " call test_setmouse(2, 25)
+  call nvim_input_mouse('left', 'press', '', 0, 1, 24)
+  call getchar() " wait for and consume the mouse press
+  call assert_equal(#{
+        \ screenrow: 2,
+        \ screencol: 25,
+        \ winid: win_getid(),
+        \ winrow: 2,
+        \ wincol: 25,
+        \ line: 1,
+        \ column: 4,
+        \ }, getmousepos())
+  " call test_setmouse(2, 50)
+  call nvim_input_mouse('left', 'press', '', 0, 1, 49)
+  call getchar() " wait for and consume the mouse press
+  call assert_equal(#{
+        \ screenrow: 2,
+        \ screencol: 50,
+        \ winid: win_getid(),
+        \ winrow: 2,
+        \ wincol: 50,
+        \ line: 1,
+        \ column: 8,
+        \ }, getmousepos())
   bwipe!
 endfunc