custom backspace

custom backspace

[Sam Halliday]

Hi all,

I'd really like an emacs configuration whereby backspace will go back one layer of indentation if the previous character is an indented whitespace, for all programming language modes.

Also, I'd really like control-backspace to be contextual so that it will eat up all the whitespace if the previous character is whitespace, or delete a word (which I think is the default) if the previous character is a non-whitespace character.

Can anybody please help me to get this set up?

Best regards,
Sam

Re: custom backspace

[Sam Halliday]

On Wednesday, 23 April 2014 00:00:46 UTC+1, Sam Halliday  wrote:
> I'd really like an emacs configuration whereby backspace will go back one layer of indentation if the previous character is an indented whitespace, for all programming language modes.
> 
> 
> Also, I'd really like control-backspace to be contextual so that it will eat up all the whitespace if the previous character is whitespace, or delete a word (which I think is the default) if the previous character is a non-whitespace character.


I should add some information to this to explain why I need some help:

1. "m-x describe-key" tells me that my "backspace" or DEL is bound to

 (backward-delete-char-untabify ARG &optional KILLP)
  
  with value untabify. But if type lots of spaces (e.g. in the scratch or my .emacs) and then press backspace, it only goes back one character at a time... not untabbing.

2. describe on my control-backspace reveals that this is bound to C-backspace. But when I try to create any form of binding for C-backspace in my .emacs I get an error that control must be followed by a single character... so I don't have a clue how to rebind this.

Help greatly appreciated :-)

Re: custom backspace

[Sam Halliday]

On Wednesday, 23 April 2014 00:15:38 UTC+1, Sam Halliday  wrote:
> But when I try to create any form of binding for C-backspace in my .emacs I get an error that control must be followed by a single character.

I've solved this small part of the problem at least: "<C-backspace>", not "C-backspace" when defining the global key. I guess now I need a little lambda that checks to see the value of the previous character and acts accordingly.

Re: custom backspace

[Paul Smith]

Not sure what "all programming modes" means to you, but you can check
out the hungry delete commands and mode in CC-mode, which covers a
number of different programming modes.  It might be interesting to see
how it works, if nothing else.

RE: custom backspace

[Drew Adams]

> 1. "m-x describe-key" tells me that my "backspace" or DEL is bound to
>  (backward-delete-char-untabify ARG &optional KILLP)
> 
>   with value untabify. But if type lots of spaces (e.g. in the scratch or my
> .emacs) and then press backspace, it only goes back one character at a
> time... not untabbing.

It *is* untabifying.  If the char before point is a tab character,
then without untabifying behavior that char is removed.  With
untabifying, the tab char is converted to SPC chars and then one of
those SPC chars is removed, instead.

> 2. describe on my control-backspace reveals that this is bound to C-
> backspace. But when I try to create any form of binding for C-backspace in
> my .emacs I get an error that control must be followed by a single
> character... so I don't have a clue how to rebind this.

Use `C-h k', then hit the `C-backspace' key.  It tells you something
like this:

  <C-backspace> runs the command backward-kill-paragraph...

Now you know how Emacs prints the name of that key sequence: <C-backspace>.
So do this:
(global-set-key (kbd "<C-backspace>") 'your-command)

See the Emacs manual, node `Init Rebinding'.