Why the HTML entity doesn't work on the Windows Chrome?

8
votes

HTML entities are not working on chrome and IE (on windows).

I have entered the following code in my page and it works fine on mac chrome or firefox or safari, but not on windows.

<span class="font-family:Arial;">&lang; &rang; 〉 〈 </span>
3
htmlhtml-entities
What doesn't work? What's the problem? What do you see? Not see? What is 〉 〈? – Rocket Hazmat
Yes, I see empty space. I don't see arrows. – tv4free
&lang ; should be &lang;. No space before the ;. – Rocket Hazmat
:) I do have it like &lang; – tv4free
Not sure if it's the problem, but font-family:Arial; is not a valid class name. I believe you want style not class. – DACrosby

3 Answers

6
votes

This is primarily a font issue, though there is a nasty silent change in HTML specs involved.

Modern browsers interpret &lang; and &rang; as referring to U+27E8 MATHEMATICAL LEFT ANGLE BRACKET “⟨” and U+27E9 MATHEMATICAL RIGHT ANGLE BRACKET “⟩”, informally known as “bra” and “ket”. This interpretation is being made official in the named character references section of HTML5.

These characters are adequate for use in many mathematical notations, and the ISO 80000-2 standard explicitly specifies that they are used e.g. for certain scalar product notations. But support to them in fonts is rather limited. In old Windows systems, no font contains them. In newer Windows systems, from Windows Vista onwards, Cambria Math should be available. It is possible that you have been testing on an old Windows version, but it is also possible that Chrome is unable to find the right font. To give it a helping hand, use a CSS rule that suggests that font, e.g. with the attribute

style="font-family: Cambria Math"

You might consider adding some other fonts to the list, using fonts that are known to contain the characters. See my Guide to using special characters in HTML.

The nasty change is that in HTML 4.01, in the entities section, &lang; and &rang; are defined as referring to U+2329 LEFT-POINTING ANGLE BRACKET “〈” and U+232A RIGHT-POINTING ANGLE BRACKET “〉”. They are logically less satisfactory (and deprecated by the Unicode Standard), but they have somewhat wider font support.

So in addition to declaring fonts that contain the characters you use, you need to decide which pair of these characters you use or whether you use something else; it's a complicated question. If you use them, it is best to use them as such (in a UTF-8 encoded HTML document) or using numeric character references such as &#x27e8;. The reason is that &lang; and &rang; should not be expected to work consistently; they probably work the HTML5 way in all modern browsers, but there is hardly any reason to take the risk, when you can unambiguously indicate the characters you want.

2
votes

That particular character is simply a unicode codepoint which is an arbitrary number. There are a lot of unicode codepoints that do not have an 'official' symbol. Even if they do have a symbol, it is not necessarily the case that your font has a symbol for that codepoint. If you choose a different font, you may end up with a different symbol.

I looked at the CSS for the page and it shows this character displaying in Arial (plus a bunch of other fonts that do not matter). Windows comes with Arial so it should always pick up that font first. It looks like Arial does not have a symbol for that unicode codepoint. Anytime you do not have a glyph for a codepoint, it puts in some form of a box indicating there is no glyph

1
votes

It depends on the entity, and the fonts on the system your reader is using. The issue is that these characters are not in the MathJax web fonts, so MathJax has to fall back on system fonts to find them. Some browsers are better at that than others. Your configuration controls what fonts MathJax lists for the browser to look in, so you may want to modify that to include fonts where you know your entities can be found (and you may want to think about the fact that you may have people reading your site on Windows, Mac, and Linux, and also mobile devices, so such decisions are not always easy).

Notice that when you install STIX fonts, it works for you. This is because STIXGeneral is in the default list of fonts that MathJax uses for unknown characters. You want to add others to that list (it is stored in the undefinedFamily property of the HTML-CSS and SVG sections of your configuration). Note however, that IE will stop checking fonts once it encounters a font that is installed on the system, even if it doesn't include the needed character and later fonts in the list do, so you have to be careful about the order that you use.