bug#9054: 24.0.50; show source in other window

[martin rudalics <rudalics@gmx.at>]

 >> Describe `setq'
 >> Lookup `setq' in Manuals
 >> Show Definition of `setq'
 >> Show References for `setq'
 >
 > But what to do with long symbols?  For example, this won't fit to any menu:
 >
 >    Describe `display-fill-column-indicator-character'
 >    Lookup `display-fill-column-indicator-character' in Manuals
 >    Show Definition of `display-fill-column-indicator-character'
 >    Show References for `display-fill-column-indicator-character'

We could abbreviate such monsters in the menu entry and show the full
identifier in the tooltip of the menu entry.

 > There is the menu “Describe” in the submenu “Help” on the manu-bar,
 > but I don't see “Describe Character” in it.

Describe Character makes most sense when the user "is right at that
character".  I think

- the menu at the top of a frame is suited for describing and helping
   with general things (and I think it does that pretty well already),

- the mode line is suitable for describing things around its window and
   the buffer it displays (but it's not very good at that yet),

- the buffer context menu is best suited for describing things around
   the position of the mouse (and we didn't have any of these until you
   started implementing it).

Keybindings (if applicable in this context, like C-h f) should be tied
to the position of the selected window's buffer or the nearest suitable
object near that position.

Thus I'd say that "Select All" has no place in the "Context Menu" but
I'm not very sure where to put it instead: Maybe in a sub-menu where we
offer to select symbol, s-expression, containing function and the entire
buffer around the mouse position.  Then we could also add a search
sub-menu that would allow to search for the symbol near the mouse
cursor.  But the place where "Select All" should really go to is the
mode line.

 > But there are other
 > Describe menu items.
 >
 >> Clicking on "x" OTOH should reveal that the Lisp reader doesn't know
 >> (yet) about "x" while clicking on "3" should reveal that the Lisp reader
 >> considers it an integer.
 >
 > I don't know what to show for an integer.

We could just say that 3 is an integer.  Clicking on any character that
is neither a symbol nor a constant should primarily offer "describe
character" which IMO is a very instructive tool users should get
familiar with early.  I think the context menu is the right place for
that although the *Help* buffer should say on the _first_ line "what it
describes" - namely a character.

 >> BTW: Show/Hide in the Options menu should allow to toggle context menu
 >> mode.
 >
 > Maybe in the next version context menu mode will be enabled by default.

Then we need an entry that allows to toggle it off.

martin