Re: [Emacs-diffs] emacs-24 d69e9f1: CC Mode: Stop Font Lock forcing fontification from BOL. Fixes debbugs#19669.

[Daniel Colascione]

On 03/20/2015 09:30 AM, Alan Mackenzie wrote:
> Hello, Stefan.
> 
> On Thu, Mar 19, 2015 at 04:56:16PM -0400, Stefan Monnier wrote:
>>>> you can handle fontification from 1,3, or 4 but not from 2.  You need to
>>>> refine the system you use to keep track of whether we're within
>>>> a `union' so that it knows that position 2 is also "within a union".
> 
>>> Well, sort of.  The problem I'm facing is that in Dima Kogan's bug
>>> #19669, the following construct appears:
> 
>>> 1. enum xxx_xxxx_xxxxxxxxxx_x
>>> 2.     {XXX_XXXXXX_XXXX_XXX,
>>> 3.      XXX_XXXXXX_XXX_XXX,
>>> 4.      XXXX_XXXXX_XXXX_XXX,
> 
>>> Note that the brace on L2 is on the same line as the first XXX_....
> 
>>> When the user types on line 4, 5, ... here, CC Mode sets the
>>> fontification region start to JUST AFTER THE { ON L2.  It is essential
>>> that Font Lock doesn't change this.
> 
>> There's your problem: your current setup needs the starting point to be
>> either before "union" or after the first open brace.
>> It breaks down if it's between the two.  That's the problem you need to fix.
> 
> Not really.  CC Mode is quite capable of handling the Font Lock region
> starting at BOL2.  The problem is, when that starting point needs to be
> after the brace on L2, Font Lock moves the starting point somewhere
> else, fouling up the font locking.  This is proving surprisingly tough
> to fix.

I don't understand. Why shouldn't I be able to tell cc-mode to fontify
*arbitrary* regions and expect it to correctly apply highlighting to
these regions? It's the idea that the region "needs to be after brace"
that I find confusing. Shouldn't jit-lock have the right to expand the
region arbitrarily?

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