[plt-scheme] Some more usability issues

Hi,

I sometimes post here some issues that make working with Dr Scheme less
convenient as it could be. Lately I ran into two new things that bother
me:

- The context menu only stays open as long as the right mouse button is
pressed. I know that this has been the historical Unix way of doing
things, but nowadays many toolkits (Windows, GTK+, AFAIR Qt too) leave
the menu open until the user does a (left or middle or right) click
outside of the menu. In my option this is the better way, since it can
be tricky to click right and move the mouse, especially on a touchpad
and when every other application leaves the context menu open.

- Search in Helpdesk for "(selection)" in the context menu. This option
is incredibly useful, but when I select a large amount of text, the
whole 'Search in Helpdesk for "large amount of text"' makes the menu
very, very large. I think it would be better to shorten it to the first
selected form and add "..." to it. The user will know that there is
some more text while not blowing up the sice of the menu.

- When running the debugger, I can't make the left part
(Stack/Variables) wider. This would be handy because the variables that
I define sometimes have a large text representation and the frequent
line breaks and scrolling in the variables window could be reduced if I
could make it larger by making the definitions and REPL parts smaller.

It would be great if someone could look into this, since DrScheme, erm,
MrEd is a really good way to program in Scheme except for the
historical usability weaknesses (some of these were already adressed -
many thanks for that, this made my MrEd experience a lot more pleasant
already).

Thanks for reading and of course thanks for MrEd!

regards,
Marek