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Friday, October 16 2015

Open Font Format 3 released: Are browser vendors good at math?

Version 3 of the Open Font Format was officially published as ISO standard early this month. One of the interesting new feature is that Microsoft's MATH table has been integrated into this official specification. Hopefully, this will encourage type designers to create more math fonts and OS vendors to integrate them into their systems. But are browser vendors ready to use Open Font Format for native MathML rendering? Here is a table of important Open Font Format features for math rendering and (to my knowledge) the current status in Apple, Google, Microsoft and Mozilla products.

Pre-installed math fontsMake mathematical rendering possible with the default system fonts.OSX: Obsolete STIX
iOS: no
Android: no
Chrome OS: no
Windows: Cambria Math
Windows phone: no?
Firefox OS: no
MATH table allowed in Web fontsWorkaround the lack of pre-installed math fonts or let authors provide custom math style.WebKit: yes (no font sanitizer?)Blink: yes (OTS)Trident: yes (no font sanitizer?)Gecko: yes (OTS)
USE_TYPO_METRICS OS/2 fsSelection flag taken into accountMath fonts contain tall glyphs (e.g. integrals in display style) and so using the "typo" metrics avoids excessive line spacing for the math text.WebKit: noBlink: yesTrident: yesGecko: yes (gfx/)
Open Font Format FeaturesGood mathematical rendering requires some glyph substitutions (e.g. ssty, flac and dtls).WebKit: yesBlink: yesTrident: yesGecko: yes
Ability to parse the MATH tableGood mathematical rendering requires many font data.WebKit: yes (WebCore/platform/graphics/)Blink: noTrident: yes (LineServices)Gecko (gfx/)
Using the MATH table for native MathML renderingThe MathML specification does not provide detailed rules for mathematical rendering.WebKit: for operator stretching (WebCore/rendering/mathml/)Blink: noTrident: noGecko: yes (layout/mathml/)
Total Score:4/63/64.5/65/6

update: Daniel Cater provided a list of pre-installed fonts on Chrome OS stable, confirming that no fonts with a MATH table are available.

Saturday, August 15 2015

MathML Accessibility (part II)

As announced in a previous blog post, I was invited to two Mozilla Work Weeks in Toronto and Whistler during the month of June. Before these work weeks, the only assistive technology able to read MathML in Gecko-based browsers was NVDA, via the help of the third-party MathPlayer plugin developed by Design Science, as shown in the following video:

Thanks to the effort done during these work weeks plus some additional days, we have made good progress to expose MathML via accessibility APIs on other platforms: Mac OS X, Linux, Android and Firefox OS. Note that Firefox for iOS uses WebKit, so MathML should already be exposed and handled via Apple's WebKit/VoiceOver. If you are not familiar with accessibility APIs (and actually even if you are), I recommend you to read Marco Zehe's excellent blog post about why accessibility APIs matter.

Apple was the first company to rely on accessibility APIs to make MathML accessible: WebKit exposes MathML via its NSAccessibility protocol and it can then be handled by the VoiceOver assistive technology. One of the obvious consequence of working with open standards and open accessibility APIs is that it was then relatively easy for us to make MathML accessible on Mac OS X: We basically just read the WebKit source code to verify how MathML is exposed and did the same for Gecko. The following video shows VoiceOver reading a Wikipedia page with MathML mode enabled in Gecko 41:

Of course, one of the disadvantage is that VoiceOver is proprietary and so we are dependent on what Apple actually implements for MathML and we can not easily propose patches to fix bugs or add support for new languages. This is however still more convenient for users than the proprietary MathPlayer plugin used by NVDA: at least VoiceOver is installed by default on Apple's products and well-integrated into their user & accessibility interfaces. For instance, I was able to use the standard user interface to select the French language in VoiceOver and it worked immediately. For NVDA+MathPlayer, there are several configuration menus (one for the Windows system, one for NVDA and one for MathPlayer) and even after selecting French everywhere and rebooting, the math formulas were still read in English...

The next desktop platform we worked on was Linux. We continued to improve how Gecko expose the MathML via the ATK interface but the most important work was done by Joanmarie Diggs: making Orca able to handle the exposed MathML accessibility tree. Compared to the previous solutions, this one is 100% open and I was happy to be able to submit a couple of patches to Orca and to work with the Gnome Translation Team to keep the French translation up-to-date. By the way, if you are willing to contribute to the localization of Orca into your language feel free to join the Gnome Translation Project, help will be much appreciated! The following video shows how Orca reads the previous Wikipedia page in Nightly builds:

On mobile platforms (Android and Firefox OS) we use a common Javascript layer called AccessFu to handle Gecko's internal accessibility tree. So all of this is handled by Mozilla and hence is also 100% open. As I said in my previous blog post, I was not really aware of the internal details before the Work Weeks so it was good to get more explanations and help from Yura Zenevich. Although we were able to do some preliminary work to add MathML support to AccessFu in bug 1163374, this will definitely need further improvements. So I will not provide any demo for now :-)

To conclude this overview, you can check the status of accessibility on the Mozilla MathML Project page. This page also contains a table of MathML tests and how they are handled on the various platforms. At the end of September, I will travel to Toronto to participate to the Mozilla and FOSS Assistive Technology Meetup. In particular, I hope to continue improvements to MathML Accessibility in Mozilla products... Stay tuned!

Wednesday, November 14 2012

Writing mathematics in emails

People writing mathematics in emails, like researchers in mathematics or physics, have probably encountered this difficulty to properly format complex mathematical formulas. The most common technique is just to write text with LaTeX-like or ASCIIMathML-like syntax and hope that the recipient will just understand the expressions. Obviously, this is not really convenient to write and read, some errors may happen and result in misunderstandings between the sender and the recipient. There are other classical issues like how to write the math (special syntax? math panel? handwriting recognition?), accessibility, rendering quality etc Of course, these issues are well-known and expected to be addressed by MathML. Since HTML is a common format for email and MathML is now part of HTML5, this is clearly a good candidate to solve the problem of mathematics in emails.

The idea to use MathML in emails is not new and was already suggested in a screenshot from the Mozilla MathML Project more than 10 years ago. Thunderbird has been able to render MathML in newsfeeds for a long time, provided that the author served his content as XHTML. I may also mention Amaya, which added support for sending a document by email in 2007, although I have never figured out how to configure it to send emails. Two years ago, I tried without success to fix a bug to display XHTML attachment inline and which could be a partial solution to the problem. Finally, one year ago Bob Mathews (from Design Science) asked me about the status of MathML in Thunderbird, and I could unfortunately not give him a better answer than what is in the present paragraph. But I hoped that MathML in HTML5 will change the situation.

Indeed, while I was working on some MathML-in-clipboard patches, I realized that it is now possible to paste MathML inside an email. After further discussions with Bob Mathews, Paul Topping & David Carlisle, I've been able to do more testing. The situation is the following:

  • Thunderbird can send emails containing MathML and render them correctly.
  • Apple Mail (used in Mac OS X and iOS) can receive emails containing MathML and should render them correctly since MathML is enabled in Apple's products.
  • Microsoft Outlook does not render MathML in emails. However the rendering is based on Microsoft Word which has MathML support. Basically, Thunderbird sends MathML in HTML5 and Word displays MathML after an XSLT conversion into Microsoft's own OMML format. Hence Microsoft might be able to do something not too complicated to make the whole stuff work.
  • Web Mail Clients like Gmail or Zimbra seem to filter the MathML in emails and so do not render it correctly. If this filter is removed, they can certainly let the browser do the rendering job or use MathJax to do so.

Now let's consider a basic example about how to send MathML in emails, using Thunderbird. One of the issue is that Gecko's editor has really been designed with only HTML-editing features in mind and if you start editing MathML formulas you are going to get some invalid markup messages or other troubles. And of course Thunderbird does not have any math panel or other WYSIWYG tools to write mathematics. However it might not be too difficult to write an add-on to add MathML editing features in Thunderbird like BlueGriffon's add-on or Firemath (these add-on might even be installed without too much trouble in Thunderbird). Or one can of course use one of the existing tools to generate MathML and just paste the code in Thunderbird. Here I'm going to use the itex2MML filter. So first write your mail in a separate text file:


Hi Matthew, I just read your email about the behavior of the factorial function and harmonic series for large values of $n$. If you denote by $\gamma \approx 0.5772156649$ the Euler's number, by $e \approx 2.7182818284$ the Euler's constant then you have the well-known Stirling's approximation:

$$n! = \sqrt{2 \pi n} {\left( \frac{n}{e} \right)}^n \left( 1 + O \left( \frac{1}{n} \right) \right)$$

where of course I use the classical constant $\pi \approx 3.1415926535$. We also have the following asymptotic expansion:

$$\sum_{k=1}^n \frac{1}{k} = \ln(n) + \gamma + O \left( \frac{1}{n} \right)$$

I hope that this answers your question.

then call itex2MML to replace the LaTeX code by <math> elements:

cat mail.txt | itex2MML > mail.html

Write a new mail in Thunderbird and use the menu "Insert ; HTML" . David Carlisle told me that you have to be sure that the "send as HTML" is enabled if it does not show up. Then just copy the mail.html source into the window:

insert MathML

Once you click the insert button, the MathML should be automatically rendered in Thunderbird:

MathML in Thunderbird

When your email is ready, just send it as usual! Here is how it appears on an iPod:

MathML in Apple Mail

Let's just hope that other mail clients will support MathML in emails!