Wildly OT: pop-up virtual keyboard for Mac or Linux?

[Ned Deily]

In article 
<CANc-5UxsR3_3qhpCubwGh+Kfpt4mk4RM1RbMxkkcuPKsEk65HQ at mail.gmail.com>,
 Skip Montanaro <skip.montanaro at gmail.com> wrote:

> I know this is way off-topic for this group, but I figured if anyone
> in the online virtual communities I participate in would know the
> answer, the Pythonistas would... Google has so far not been my friend
> in this realm.
> 
> One of the things I really like about my Skype keyboard (and likely
> other "soft" keyboards on Android) is that when you hold down a "key"
> for a brief moment, a little mini keyboard pops up, from which you can
> easily choose various accented variants and other symbols. For
> instance, If I press and hold the "d" key, I see these choices (ignore
> the capitalization of the first letter - my mistake sending a text
> message to myself from my phone, and I can't seem to convert it to
> lower case):   –|õ&d©£ď
> 
> While I'm a touch typist, I almost never use auto-repeat, which is the
> "binding" of held keys in most environments (curse you, IBM and your
> Selectric!). These days I find my self needing accented characters
> much more frequently than key repeat (C-u 2 5 - suffices in Emacs to
> bat out 25 hyphens). Being an American with an American keyboard, I
> haven't the slightest idea how to type any accented characters or
> common symbols using the many modifier keys on my keyboard, and no key
> caps display what the various options are. And I'm getting kind of
> tired of going to Google and searching for "degree symbol". :-/
> 
> Is there an X11 or Mac extension/program/app/magic thing which I can
> install in either environment to get this kind of functionality? I'm
> thinking that if you hold down a key for the auto-repeat interval,
> instead of the key repeat thing making all sorts of duplicates, a
> little window would pop up over/near the insertion point, which I can
> navigate with the arrow keys, then hit RET to accept or ESC (or
> similar) to cancel. It need not be perfect. It might (for example)
> only work in certain environments (Chrome, Emacs, vim, Firefox).
> Anyplace to start. It need even be written in Python (though that
> would be cool.) I think that once something like this caught hold, it
> would fairly quickly take over from the dark lords of auto-repeat.

On OS X, the system provides both a "Character Viewer" (which allows the 
selection of any Unicode character and a "Keyboard Viewer" (which allows 
you to see the keyboard key mappings as keys and modifiers are pressed).  
Both can be enabled from System Preferences (System Preferences -> 
Keyboard -> Keyboard on current 10.10 systems).  As of OS X 10.7 (I 
believe), there are also now popup menus that appear when various keys 
are held down that show accented variants of the character (this is 
similar to what iOS on the iPhone and iPad provide).   Unfortunately, 
this doesn't work with some applicatons that do not use the full 
built-in text system; the Tk implementations on OS X are such 
applications so the popups don't work with Tkinter apps like IDLE.  Nor 
does it work with X11 apps.

-- 
 Ned Deily,
 nad at acm.org