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Similar to How to change GUD breakpoint keybinding to the old one but I would like to bind CTRL+x followed by SPACE to be gud-break.

What I have working (well it is a hack; keep reading) is:

  (define-key ctl-x-map " " 'gud-break)

but ctl-x-map is a global variable akin to the global map. And in fact, if I switch to another C++ buffer and type C-h k C-x SPC I get:

C-x SPC runs the command gud-break (found in global-map), which is an interactive compiled Lisp function.

It is bound to C-x SPC, C-x C-a C-b.

(gud-break ARG)

Set breakpoint at current line.

which means the global definition across all buffers is what was changed, which is not correct AFAIK.

Is there a way to "insert" or somehow affect the local key map for C-x, which I believe is gud-mode-map, because I want that binding to not be global for all C++ buffers. E.g., the global binding for CTRL+x followed by SPACE is rectangle-mark-mode.

Yes I realize the standard binding is C-x C-a C-b for gud-break, but that is asking for RSI.

Update #1

Since I need the local key map for gud-mode-map, this needs to be active only when I'm running a debugger. In my case, this is in C++ mode buffers, but my understanding is that gud-mode-map becomes active in those C++ mode buffers only during the debug session, and is removed from the key bindings when gud mode is finished.

Update #2

This did not work:

(define-key gud-mode-map [(control x ?\ )] 'gud-break) ;; <-- gave "Two bases given in one event" error too.
(define-key gud-mode-map (kbd "C-x SPC") 'gud-break) ;; <-- this does not work either.

Update #3

As an experiment, I commented out my define-key bindings in my hook I add to gud-gdb-mode-hook, reran gdb, then switched to the gud buffer (not the C++ source file) and typed C-h k C-x SPC I get this:

C-x SPC runs the command gud-break (found in gud-mode-map), which is
an interactive Lisp closure.

It is bound to <menu-bar> <debug> <break>, C-x SPC, C-c C-b, C-x C-a
C-b.

(gud-break ARG)

Set breakpoint at current line.

But then when I switch over to the C++ buffer that should also have the same bindings inserted temporarily (while gud mode is active), and then do the same thing I get this instead:

C-x SPC runs the command rectangle-mark-mode (found in global-map),
which is an interactive autoloaded compiled Lisp function in
'rect.el'.

It is bound to C-x SPC.

(rectangle-mark-mode &optional ARG)

Toggle the region as rectangular.
Activates the region if needed.  Only lasts until the region is deactivated.

Switching back to the gud buffer, and typing C-h m shows this:

Debugger mode defined in 'gud.el':
Major mode for interacting with an inferior debugger process.

   You start it up with one of the commands M-x gdb, M-x sdb, M-x dbx,
M-x perldb, M-x xdb, or M-x jdb.  Each entry point finishes by executing a
hook; 'gdb-mode-hook', 'sdb-mode-hook', 'dbx-mode-hook',
'perldb-mode-hook', 'xdb-mode-hook', or 'jdb-mode-hook' respectively.

After startup, the following commands are available in both the GUD
interaction buffer and any source buffer GUD visits due to a breakpoint stop
or step operation:

C-x SPC sets a breakpoint at the current file and line.  In the
GUD buffer, the current file and line are those of the last breakpoint or
step.  In a source buffer, they are the buffer's file and current line.

...

Notice the reference to C-x SPC above. It is as if they intended to bind C-x SPC but it did not work, or something is preventing it from being bound properly in that buffer when gud mode is entered.

bgoodr
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  • You say you want the binding to be local but you don't say local to what. IOW, in which buffers would you want `C-x SPC` to call `gud-break`? – Stefan Jun 14 '18 at 18:26
  • @Stefan I just updated the end of the question to clarify. – bgoodr Jun 15 '18 at 01:42

2 Answers2

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I'm not exactly clear on what you want. But if you only want to redefine the key C-x SPC when the gud-mode-map is active, then tell define-key you want to use that map: (define-key gud-mode-map ...).

Mark Skilbeck
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  • Thanks and you are on the right track, but that did not work for me. See Update #2 inside my description for what I've tried. Perhaps my `(kbd...)` needs adjustment? – bgoodr Jun 15 '18 at 13:20
  • @bgoodr After having done `(define-key gud-mode-map (kbd "C-x SPC") 'gud-break)` and are in `gud-mode`, what does `C-h C-x SPC RET` show? – Mark Skilbeck Jun 20 '18 at 20:15
  • `C-h C-x SPC` is not what I think you meant because doing so gives `C-h C-x SPC` is undefined. I suspect what you meant was `C-h k C-x SPC` to use `C-h k` (for `describe-key`) and then type `C-x SPC`. So I did that and got `C-x SPC runs the command rectangle-mark-mode`. I did that from within a C++ buffer under gud-mode. – bgoodr Jun 22 '18 at 00:39
  • But this is strange. Shouldn't `describe-mode` show something about the gud mode being somehow "active"? I'm not seeing any reference to anything with "gud" in it in the Help buffer that results. – bgoodr Jun 22 '18 at 00:42
  • Added Update #3 to main description in hopes it will help solve this puzzle. I'm still baffled. – bgoodr Jun 22 '18 at 01:08
  • Giving up and answering my own question at https://stackoverflow.com/a/50979549/257924. But if anyone has any simple solutions to avoiding the `C-x C-a` prefix that would be good, but I doubt it is possible at least not cleanly for all bindings for gud mode. – bgoodr Jun 22 '18 at 01:47
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I've chosen to give up on this altogether. using C-x SPC in the buffer is problematic anyhow. I noticed that the C-x C-a prefix that is used for the gud bindings are left in the C++ buffer even after gud finishes, so the gud mode is not cleaning up after itself anyhow.

bgoodr
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