Re: Line wrap reconsidered

[Yuan Fu <casouri@gmail.com>]

> On May 25, 2020, at 3:31 PM, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> 
>> I’ve implemented and used a lisp-based line-wrapping feature for a while and
>> it’s still sub-optimal for me. I now want to try to explore if I can add it
>> directly to redisplay. 
>> 
>> Here is what I come up with: in redisplay code, instead of only checking for
>> whitespace, check for a ‘no-wrap text-property, if the character has this
>> property, don’t wrap before[1] this character (or maybe it can be the
>> opposite, only wrap when the character has a ‘can-wrap property). And this
>> text property is calculated and applied once. 
> 
> I don't think I can discuss the quality of this proposal without first
> understanding the intended use cases (including who/how/when the
> property would be added).
> 

I’ve added the intended use case on the previous message. I’m not sure when to add the property yet. Right now I only have a general idea of using text property as a cache, so the more complex wrapping rule does not slow down redisplay. There could be a table specifying a mapping from unicode ranges to “wrappablility” (can/can't wrap before/after) and some one will iterate each character and apply the text property. The good thing is that this “wrappability” property of a character never changes, so we only need to calculate it once.

The redisplay code doesn’t need to change greatly since checking for “wrappability” is similar to checking “whitespace_p”.

Yuan