4

I'm aware of and use whitespace-mode to great effect. I don't show a glyph/character for spaces because I think it's too noisy and unnecessary. I do highlight trailing spaces red which is great.

Aside from that, I was thinking that it may be useful to specify a glyph such as ·, if it were possible, for inner consecutive spaces. This means that it excludes trailing whitespace as well as indentation, for example:

print("one·····two");

instead of:

print("one     two");

But again, this wouldn't apply to leading/indentation whitespace nor trailing whitespace.

Is this possible?

EDIT: I tried setting whitespace-regexp-search as:

(setq whitespace-space-regexp "[^ ]\\( \\{2,\\}\\)[^ ]")

I have spaces and space-mark in my whitespace-style:

(setq whitespace-style
      '(face indentation trailing empty spaces space-after-tab
        space-before-tab tab-mark space-mark))

However, it seems like the whitespace-space-regexp is only for the spaces face highlighting, and isn't used for setting the space-mark. Here's the effect:

img

Notice that all other spaces are still showing the space-mark, even though what I'd like is for consecutive spaces of 2 or more to show it. The inner consecutive spaces are indeed being highlighted differently, but I only did that to show the difference between what's being matched by whitespace-space-regexp and the space-mark character.

In fact I just noticed that even the numberline is showing the space-mark.

It looks like the space-mark is simply matched based on a character, which I guess makes sense, so perhaps this isn't possible after all.

Note: As outlined in my post, I recognize that this isn't possible via whitespace itself, what I'm curious about is whether it's possible to do at all. I found some uses of font-locking such as this one which accomplish replacing pattern matches with a character. I'm wondering if it would be possible to use something like this but have it replace the spaces in the region matched with the middle dot for example.

  • It is possible to draw an overlay that looks like a middle dot at the desired locations, but it would not be as efficient as setting up a font-lock rule and setting up a highlight of some sort at the desired locations. The answer by JeanPierre is correct, but doesn't provide either of the above-mentioned solutions/workarounds. – lawlist May 18 '16 at 17:15
  • Yeah I saw some people doing some things with font-lock rules where they would use compose-region to like replace one string with another, such as this one, but I can't figure out how to make it replace the region with another string or replace all spaces in the region with the middle dot with something like subst-char-in-region. Is that even possible? – Jorge Israel Peña May 18 '16 at 20:06
  • @lawlist So that I can enhance my answer, you mean: there's no solution provided by whitespace mode but one could use overlays to achieve that; right? What's the second solution/workaround? – JeanPierre May 19 '16 at 7:13
  • @JeanPierre -- I've given it some thought and don't have a really good solution. I do a lot of stuff with overlays in the visible window, but I programmatically need to recalculate each command loop -- so depending on what's going on, it may not be that efficient. I have never been impressed by the composition library, perhaps because it is not 100% compatible with my preferred courier font on OSX. The easiest and most workable solution would be for the original poster to just settle on a face attribute like overline/underscore/strikethrough instead of a middle dot and use a font-lock rule. – lawlist May 19 '16 at 14:18
  • @lawlist Fair enough, that's good to know. The reason I'm not inclined to just use a face attribute is that the point of using a dot glyph was to give an idea of how many spaces were there. Making it overline, underscore, strikethrough, or even just a background color doesn't serve that end. Thanks for the information though, I'll mark JeanPierre's answer. – Jorge Israel Peña May 19 '16 at 19:31
3

Indeed you can't specify different glyphs for different kinds of spaces because this feature makes use of a display table. The relevant values in variable whitespace-style are (emacs manual):

space-mark Draw space and non-breaking characters with a special glyph.

tab-mark Draw tab characters with a special glyph.

newline-mark Draw newline characters with a special glyph.

All other values specify highlights, so all other distinctions can only be made through the use of faces.

See my answer on a related question.

  • Thanks JeanPierre. I realized this, what I'm wondering about is if it's possible to do in emacs at all, for example via font-locking. – Jorge Israel Peña May 19 '16 at 7:25

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