Re: C Mode: acceleration in brace deserts.

[Lennart Borgman]

On Fri, Dec 4, 2009 at 11:34 AM, Lennart Borgman
<address@hidden> wrote:
> Hi again Alan,
>
> On Thu, Dec 3, 2009 at 8:57 PM, Lennart Borgman
> <address@hidden> wrote:
>> Hi Alan,
>>
>> On Thu, Dec 3, 2009 at 8:39 PM, Alan Mackenzie <address@hidden> wrote:
>>> Hi, Lennart!
>>>
>>> The state of this cache is held entirely in the variables (all of them
>>> buffer local) initialised thusly:
>>>
>>> (defun c-state-cache-init ()
>>>  (setq c-state-cache nil
>>>        c-state-cache-good-pos 1
>>>        c-state-nonlit-pos-cache nil
>>>        c-state-nonlit-pos-cache-limit 1
>>>        c-state-brace-pair-desert nil
>>>        c-state-point-min 1
>>>        c-state-point-min-lit-type nil
>>>        c-state-point-min-lit-start nil
>>>        c-state-min-scan-pos 1
>>>        c-state-old-cpp-beg nil
>>>        c-state-old-cpp-end nil)
>>>  (c-state-mark-point-min-literal))
>>>
>>> , where `c-state-mark-point-min-literal' merely sets 3 variables already
>>> named.  I don't honestly see a way MuMaMo could disturb this state by
>>> accident.
>>
>>
>> Thanks. Mumamo needs to know because it switches major mode and that
>> normally kills buffer local variables.
>
>
> I have a bit trouble with this. I believe there is a simple solution,
> but it requires some low level changes to Emacs. Your changes here
> illustrates very well why such a change may be desireable to support
> mult major modes.
>
> You are parsing the buffer from the beginning to find a state at a
> point (this state is here "in literal or not"). This of course breaks
> if there are chunks with different major modes in the buffer.
>
> All parsers naturally behave like this (unless they are not
> specifically taught about multi major modes and its implementation).
> js2, semantic, font-lock are other examples.
>
> I think the easiest cure for this is to let them just see the parts of
> the buffers that are in the programming language they know of at the
> moment. (This is perhaps not enough but a good start that covers most
> possibilities - and can be used for all parsers.)
>
> This must however be implemented on a low level. All C primitives
> reading the buffer must know about it. It is probably in most cases
> straightforward to implement it. A level between the buffer reading
> primitives and the buffer content is needed.  This hides the parts
> that should not be seen.
>
>
> It is probably possible to support your changes in MuMaMo now, but it
> is not easy while it will perhaps break easily instead. I have done
> something similar to syntax-ppss. I wish we could have the low level
> change instead.


Just a question I forgot: Why are you not using syntax-ppss here? Are
you not looking for the same thing (ie inside comment or string).

If you did it that way then it would already be supported by MuMaMo.