Window display bug

[Nick Roberts]

The change:

2003-04-30  Richard M. Stallman  <address@hidden>

        * xdisp.c (move_it_vertically_backward): Do the final big else
        even if nlines is 0.

has introduced a bug where the window doe not move to display the cursor at
point. I have code where I can move point onto succesive lines and see the
line number increment on the mode-line and yet the display does not change.  A
static cursor does display but not where it should. The bug goes away when I
revert the change. I don't understand the code but experimenting suggests that
the problem only occurs if a display margin is present (at least on the left
hand side). Perhaps, in this case, the variable nlines should be computed
differently.

Nick