Re: [21.1.50]: menu-bar-update-hook run multiple times on menu-ba r cl icks.

[Richard Stallman]

    However, I still see multiple runs of this code---that is the outer
    condition succeeds---even when scrolling.  My first guess was that is
    down to lazy fontification: as I scroll down the buffer, windowfuls are
    fontified and the buffer-modified-tick changes as text properties are
    placed on buffer text.  This problem bites both lazy lock and jit lock.

select-window sets windows_or_buffers_changed.  So does altering a
buffer other than the one displayed in the selected window.  That
might be the cause--is it?

The reason for the latter is to cause the other windows to be
redisplayed.  There is no need to cause recalculation of menu bars in
that situation.  So we could solve the problem by splitting
windows_or_buffers_changed.  We could add a variable
other_buffers_contents_changed, set that for changes in other buffers,
and it could have some but not all of the effects of setting
windows_or_buffers_changed.

select-window would need to set other_buffers_contents_changed
if the displayed buffer of the previous selected window had
been modified.

save-selected-window would need to restore windows_or_buffers_changed.
This would require some of the changes I suggested in a previous message.