bug#42406: Mouse-wheel scrolling can be flickering

[martin rudalics]

> set-window-start is how Lisp programs tell the display engine to
> scroll the display.  So if we agree that scrolling should trigger
> update of the frame's elements other than the selected window,

Personally I don't agree but happily leave this decision to others.

> then
> these calls to wset_update_mode_line are necessary and cannot be
> removed.
>
> As I said previously, patches are welcome to make the decision of what
> exactly needs to be redrawn more fine-grained than the current "either
> just the selected window or all the windows on all the frames" method.

We talk here about a workaround Konrad would use in his personal builds
to avoid that scrolling a window slows down his system until something
better is available.  Or what would you do in his place?

martin