• ## Discussion Feed

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1.

@Anton: I tried clearing my cache, but it's still doing it in both versions of Firefox.

2.
On my question:

http://mathoverflow.net/questions/59046/can-you-flip-the-end-of-a-large-exotic-mathbbr4

inclusion of \langle and \rangle latex tags makes rendering on a mac, with the latest chrome, and on an iPad, with the latest safari, place the < and > incorrectly and also sometimes places surrounding text incorrectly also.
3.
In the above question after adding some back-ticks the problem seems to go away on OS X chrome, but stil live on in iPad safari. Meh.
4.
MathJax has trouble being printed with Opera (it looks fine on-screen). Often, there are blank spaces instead of formulas or alignment errors. For example, I couldn't print the answer to the following question with Opera.

http://mathoverflow.net/questions/32387/computation-of-homology-groups-of-m-g-n
• CommentAuthorshogun70
• CommentTimeMar 22nd 2011 edited

@Evan, @Anton,

For cross-site use (e.g. resources residing on latex.mathoverflow.net) Firefox requires font-files to be delivered with the HTTP header
Access-Control-Allow-Origin: *

On mathoverflow this header isn't set so the font-files aren't applied and MathJax falls back to font images.
This HTTP header is also required for cross-site font-files in IE9.

For Apache, something like the following in an appropriate .htaccess file would work:
<FilesMatch "\.(otf|eot)$"> <IfModule mod_headers.c> Header set Access-Control-Allow-Origin "*" </IfModule> </FilesMatch> EDIT: Actually, I forgot that this is already in the documentation. See the Notes about Shared Installations at http://www.mathjax.org/docs/1.1/installation.html • CommentAuthorshogun70 • CommentTimeMar 22nd 2011 edited @Anton, I also noticed that resources residing on latex.mathoverflow.net (basically MathJax) don't seem to be gzip'ed. All files in the MathJax distribution can be reduced with gzip, with the exception of png files (for image fonts). In Apache, something like the following might be appropriate: AddOutputFilter DEFLATE html xhtml css xml svg js eot otf ttf 5. @shogun70: We already have such an .htaccess file. See this thread. @Scott M: (not in response to anything he's posted here recently) How much control do you have over Apache? Can you tell it to gzip MathJax as shogun70 suggests? • CommentAuthorshogun70 • CommentTimeMar 23rd 2011 @Anton, Using the following curl -D headers.txt http://latex.mathoverflow.net/mathjax/fonts/HTML-CSS/TeX/otf/MathJax_Main-Regular.otf > /dev/null I do see the Access-Control-Allow-Origin header. Using curl -D headers.txt http://latex.mathoverflow.net/mathjax1.1/fonts/HTML-CSS/TeX/otf/MathJax_Main-Regular.otf > /dev/null I do NOT see the header. 6. @shogun70: Holy moly, you're right! It looks like I screwed up the upgrade to MathJax 1.1 and called the file .htacess instead of .htaccess. It should be corrected now. Thanks for catching this! 7. I'm pretty sure I don't need to do anything further, but for future reference we can control exactly what is controllable via .htaccess files, and nothing more. On the other hand, if it ever comes to it we have some alternative hosts (sitting under various people's office desks, in Toronto or Berkeley) where I have root access and full control of apache. 8. It's comments like that which make me wish that meta.MO had a soundtrack. There ought to have been some menacing music building to a crescendo at the words "root access" (with possibly some manic laughter off-stage). • CommentAuthorshogun70 • CommentTimeMar 24th 2011 @Scott: I assume latex.mathoverflow.net is hosted at dreamhost .com. The dreamhost wiki indicates that the DEFLATE output filter is available, see http://wiki.dreamhost.com/DEFLATE and can be included in .htaccess files. 9. Okay, I think I added the DEFLATE filter. Could someone (@shogun70?) check that it's working? Actually, I'm a bit confused about our .htaccess files for latex.mathoverflow.net. @Anton, the .htaccess I added a line to didn't have anything about "Access-Control-Allow-Origin", and I couldn't find any others. Where did you do this? 10. The htaccess file handling the fonts is in mathjax1.1/fonts/HTML-CSS/TeX/otf/, like the MathJax docs recommend. • CommentAuthorshogun70 • CommentTimeMar 29th 2011 @Scott: Yes, the files are being gzip'ed now. @Anton: You've found a MathJax documentation error - that location will work (is working) for .otf files (needed for Firefox) but not .eot (needed for IE9). I can't check mathoverflow.net with IE9 until tomorrow, but I assume it is rendering math with image fonts. The mathjax1.1/fonts/HTML-CSS/TeX/otf/.htaccess file should be moved to an ancestor directory of the one it is currently in, or merged with the .htaccess file in the top directory (mathjax1.1/.htaccess). 11. @shogun70: Thanks for all your help! I've moved the .htaccess file to the parent directory. Now otf and eot files appear to have the correct headers. • CommentAuthordthurston • CommentTimeMay 14th 2011 I asked this as a separate discussion, but probably it belongs here. The command \mathit seems to be completely ignored in LaTeX input. This yields exceptionally ugly results at times, eg, here. Why does this happen, and can it be fixed? (\textit likewise does not work right.) 12. @dthurston: could you include a screenshot? It doesn't look particularly ugly to me. I've tried both HTML+CSS and MathML rendering on Firefox 3.6.16 on Ubuntu (Edit: they look like and , respectively, but not as pixilated) • CommentAuthordthurston • CommentTimeMay 14th 2011 @Anton: your second snapshot is about what I see, and is horrendously ugly. I'm very surprised you don't see that. Look at the spacing between the 'f's. It's doing the thing TeX does by default, which is to typeset anything in math mode as though it were a product ("D times i times f times f"), which is not all what is intended. 13. @dthurston: yes, I agree that the second one is ugly, though I wouldn't have called it exceptionally or horrendously ugly. Perhaps somebody here knows if this is an issue with how MathJax converts to MathML or with how Firefox renders MathML. It's probably a good idea to ask on a MathJax forum. • CommentAuthordthurston • CommentTimeMay 17th 2011 I doubt it's a rendering issue, since it also shows up for me in Chromium. This is obviously and typically a conversion issue; this is what you get if you just enter italic text in math mode without protection. See also theojf's answer in the separate thread I started on this, before realising it should be here. If you want me to report the bug, I need to know details like which version of MathJax you're using and how it's configured. • CommentAuthorgeraldedgar • CommentTimeMay 18th 2011 edited Is it something I did? In my answer at http://mathoverflow.net/questions/65288 the display does not TeX. I copied it from the Question, then made a few changes. • CommentAuthordthurston • CommentTimeMay 18th 2011 geraldedgar: I think the double dollar signs confused the parser, or maybe the subscripts. I added backquotes around the displayed math and it fixed the issue. 14. Thanks for fixing the display. Is this remedy in an FAQ somewhere? 15. If it was the subscripts, that's a known issue that's been discussed on meta before. Subscripts and asterisks are both parsed as MarkDown and occasionally need to be escaped by a backslash to be used properly. 16. Is this remedy in an FAQ somewhere? http://mathoverflow.net/faq#latex , where it says "workaround". • CommentAuthorL Spice • CommentTimeJul 3rd 2011 edited The processor gets confused on the admittedly complicated case where a \text block contains math. For example, I couldn't typeset the legitimate TeX code \Ext^1_{\text{$\mathbb F_p$-alg}}. (It is surely possible, but I think unsatisfactory, to type instead \Ext^1_{\mathbb F_p\text{-alg}}.) 17. Just use $$...$$ for the nested math, instead of$ ... \$.
• CommentAuthorvoloch
• CommentTimeJul 31st 2011

When viewing an MO page, I got a pop-up telling me to go to this page: http://www.mathjax.org/help/configuration/

I assume this needs to be done server-side.
18.
In this answer http://mathoverflow.net/questions/73120/torsion-free-tensor-powers/73161#73161 , I define a macro \mm for \mathfrak{m}. It shows correctly in the preview, but when I load the actual answer I get a red \mm everytime I have used it.

Details:
Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.20) Gecko/20110803 Firefox/3.6.20

UPDATE: Nevermind, I just realized that I defined the macro after I used it (fixed now). So the peculiar behavior is that preview let me get away with it, not that the main page didn't.
19.

Probably MathJaX read the definition in the textarea which comes before the preview box and so the newcommand was in effect when the preview box was parsed. This relationship was, obviously, changed when you saved your answer.

20.

MathJax doesn't ever read the text in the textarea, but it does read the preview box over and over in order to update the preview. Once it learns the macro, I think it remembers it until you move to a different page.

21.

I'm getting the same kind of popup voloch mentioned several weeks ago. Whenever I load a mathoverflow page, I get the following popup message:

MathJax no longer loads a default configuration file; you must specify such files explicitly. This page seems to use the older default config/MathJax.js file, and so needs to be updated. This is explained further at

http://www.mathjax.org/help/configuration

Added: Clearing my browser cache seems to fix it.

22.

The popup voloch and Charles is confusing, since nothing has changed in our MathJax configuration for a long time.

23.
The LaTeX \begin{enumerate} command seems not to work either with or without back tics. Is there a good substitute?
24.

Bill,

That's a text command, not a maths command. MathJaX only supports mathematics commands (well, a subset thereof). If you really want to use proper LaTeX to write MO posts, contact me by email.

In the meantime, lists are done by Markdown syntax:

1. First item
1. Second item
1. Third item


Produces

1. First item
2. Second item
3. Third item
25.
Thanks, Andrew.
26.

I'm running ff3.6 (not my choice - my work won't upgrade), and I'm getting math processing errors all round.

27.

I used

<a href="http://en.wikipedia.org/wiki/Johnson%E2%80%93Lindenstrauss_lemma">Wikipedia</a>

in a post, but it did not render properly. I see that it also does not render here on Meta at all. Why? Survit edited it to

Wikipedia

which worked fine, but I thought ordinary HTML links worked.

28.

Almost certainly it's the underscore. Try backticks surrounding the a tag.

More generally, Markdown and HTML are not really meant to mix. (That is, the <pre>text</pre> syntax is preferred to using <a> tags), but of course it's convenient to do so. This sometimes results in some bumps.

29.

Hehe, witness above my failed attempt to use a <pre> tag to prevent Markdown parsing the square brackets. Bumps indeed!

30.

I tried backtics--they did not work no matter where I placed them.

31.

(This isn't a MathJaX isssue, by the way.)

The link (and Scott's <pre> attempt) doesn't work here because the Markdown filter here strips out HTML tags before processing. So any HTML tags get escaped. (Although this stripping is not 100% safe).

On MO, some HTML is allowed, including <a> tags (what is and isn't allowed is governed by a "whitelist" that is listed somewhere on meta.SO). When I cut and paste the code you gave into a blank "Ask a Question" then the preview converts it to a link. So either there's a difference between the preview and what is actually rendered (unlikely in so simple an example) or there's more to your example than just the link. Could you link to the actual post?

More generally, Markdown and HTML are not really meant to mix.

That is about as wrong as it can be! Markdown and HTML are meant to mix. Markdown goes out of its way to be polite to HTML: if it spots any HTML then it says, "I assume that the user knows what they are doing and will just let this go through.". The problem is that many people who've implemented their own version of Markdown have decided that the average user does not know what they are doing and so put in a pre-filter to strip out anything Bad. These pre-filters are complicated because they have to understand both HTML and Markdown. What they should have done is put in a post-filter to check that the final rendering is clean as the post-filter only has to understand HTML.

(Naturally, the nLab and the nForum get it right.)

32.

It's on

http://mathoverflow.net/questions/79388/minimum-space-dimension-to-place-n-points-knowing-pairwise-distances/79395#79395

Andrew.

33.

It isn't the underscore, it's the dash. Whoever created that page on Wikipedia used an ndash to hyphenate the names. Whilst this is technically correct, it makes the link somewhat tricky to type in! You need to be able to type in unicode URLs. StackExchange's Markdown parser only allows certain things in its HTML (see my comment above about sanitising). It would seem that unicode is not allowed. So what Survit did was to replace the unicode character by its "escaped" version - that's the percent stuff.

There's ways to find these escapings, but I don't know of one off-hand. (I would have thought that Wikipedia would automatically make redirects to "sanitised" versions of pages, but I can't find one for that page itself).

Usually, Markdown's own syntax for links is better than using raw HTML, but in this case even that doesn't work. The escaping method is the only one that I can make work correctly. (On the other hand, the Markdown syntax does work correctly here: [Wikipedia](http://en.wikipedia.org/wiki/Johnson–Lindenstrauss_lemma) correctly produces Wikipedia).

I just tried on the SE2.0 system and witnessed the same behaviour, so this wouldn't be fixed by migrating!

34.

I would have thought that Wikipedia would automatically make redirects to "sanitised" versions of pages, but I can't find one for that page itself

Turns out that it does. There was another problem with the URL that you put in: the / at the end. The correct URL doesn't have that. Somehow in my experimenting with replacing the dash then I overlooked the slash and got false negatives.

Incidentally, when I cut-and-paste the URL using my browser from the page in question, then it gets correctly escaped. That is, when cut-and-pasting here I get:

http://en.wikipedia.org/wiki/Johnson%E2%80%93Lindenstrauss_lemma

Replacing the en-dash by an ordinary hyphen also works:

http://en.wikipedia.org/wiki/Johnson-Lindenstrauss_lemma leads to this link. If you click on that, then you'll notice that it goes to the correct page but just below the title is a little "Redirected from ..." message which tells you that the URL that you typed wasn't the real page name, but an alias.

• CommentAuthorEmil J
• CommentTimeOct 31st 2011

Yes, IME, the browser (Firefox) escapes all cut-and-paste URLs automatically so that it all works out, but I suspect that some other browsers may get it wrong. As for replacing en-dashes with hyphens, this only works on Wikipedia because they have a general policy asking article authors (or renamers) to provide redirects in such cases, it is not guaranteed to work in general on other sites.

35.

Thanks, Andrew. I do not understand your comment about / at the end as I did not put one in...

36.

If you look at the source of your original post, it reads:

In the URL, there is a /. Since I cut-and-pasted from that to do all my experiments, a lot of them had a trailing slash. Sometimes that doesn't matter, sometimes it does. I will freely admit that I should have spotted that and removed it before doing further analysis. Ultimately, the en-dash was the real reason why it didn't work, the trailing slash was what meant that I didn't spot that putting in an ordinary hyphen did work.