bug#64596: 30.0.50; On FIXME: in src/buffer.c:1481 (force-mode-line-update)

[Stefan Monnier]

> Then I guess you or Ihor (or both) should try removing that line and
> run with that for a while.

FWIW, I've been running without those two lines ever since I put this FIXME.

> Alternatively, maybe in the case of ALL non-nil the code should set
> the prevent_redisplay_optimizations_p flag of all the buffers that are
> displayed in some window, since some redisplay optimizations are not
> eligible when the mode-line is about to be updated.

Any reason why the corresponding optimizations don't consult the
`update_mode_lines` var (or the `update_mode_line` buffer flag), or
maybe have redisplay start by propagating the `update_mode_line` buffer
flag to `prevent_redisplay_optimizations_p`?


        Stefan