[LyX/master] Make all unbreakable spaces of the same Color_latex color

[Daniel]

On 24/6/20 8:46, Daniel wrote:
> On 2020-06-24 08:15, Daniel wrote:
>> On 2020-06-23 23:46, Jean-Marc Lasgouttes wrote:
>>> Le 23/06/2020 à 23:11, Jean-Marc Lasgouttes a écrit :
>>>> commit 49e1466f93b63b0489549d40ebbde944eff1c7f6
>>>> Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
>>>> Date:   Tue Jun 23 23:33:37 2020 +0200
>>>>
>>>>      Make all unbreakable spaces of the same Color_latex color
>>>>      Of course, this means that negative spaces cannot be recognized 
>>>> anymore.
>>>
>>> I did not mean to commit this yet, but it is a good occasion to 
>>> discuss the issue of space color. I can revert that if needed.
>>>
>>> I am not sure what was the logic of colors right now.
>>
>> A wild guess on the logic:
>>
>> There are two visual dimensions at which spaces are distinguished: 
>> color (red/blue) and height (high/low)
>>
>> high/blue: positive (normal) spaces
>> high/red: negative spaces
>>
>> It makes sense to me that these spaces fall into one category (high) 
>> and that positive/negative is distinguished as blue/red.
>>
>> Then there are two more spaces left:
>>
>> low/red: protected
>> low/blue: interword
>>
>> To distinguish them from the other spaces they are low. To distinguish 
>> them from each other (and don't introduce new colors) they are red/blue.
> 
> I don't find the last red/blue distinction for special spaces nice 
> because it is used for negative space too and the high/low distinction 
> is hard to see. Instead for these special spaces, there could be a a 
> (blue) tilde (˜), as used in LaTeX, on the middle or bottom of the line 
> for a protected space instead of the "space-box". I am not sure what 
> would be a good symbol for the interword space though: maybe also the 
> latex symbol (\) or a (blue) bullet (• or ◦), as used commonly to mark a 
> normal space, on the middle or bottom. Though I am not sure whether 
> those symbols interfere with some other symbols (like linguistic ones or 
> so). Others might know.

ps. Also, a symbol works here because these special spaces don't need to 
be stretched.