Created attachment 15008 [details] [review]
Proposed patch

Created attachment 15009 [details] [review]
Proposed patch

Created attachment 15010 [details] [review]
Proposed patch

Wow!  Why did bugzilla creat three proposed patches?   Well, they are
all the same patch.   

This patch connects a callback function to the key-press-event of the
menu buttons.

Hi Rich,

My proposed patch only implements a fix for pressing the space bar on
a menu button.  You will need to add code to handle the accelerators
such as 'S', 'A', etc.  You can put the code into the
menu_button_key_press_cb() function.

Good night,
Dennis

Hi Dennis. Thanks! I'm just looking at this patch
now. What did you mean by "You will need to add code 
to handle the accelerators such as 'S', 'A', etc.".
These seem to work just fine. In other words, I
can type "A9" to set the accuracy to 9 numeric places
still, with just this patch applied.

One thing I have noticed is that the menu comes up
where the mouse pointer is. I think it would prolly
be better to have it coming up rooted on the button that's
currently got the focus. I'm just investigating how to
do that.

Owen Taylor helped me with the adjustment to show
the menu over the button that has focus (rather than
where the mouse pointer is currently located).
Patch adjusted accordingly. Fixed in v4.2.69.