The importance of Tagalog to Burmese, aka "Of course I'd lie to you, I'm a font!"

by Michael S. Kaplan, published on 2008/04/18 03:01 -04:00, original URI: http://blogs.msdn.com/b/michkap/archive/2008/04/18/8403631.aspx

Content of Michael Kaplan's personal blog not approved by Microsoft (see disclaimer)!
Regular readers should keep in mind that all I said in The End? still applies; the allusion to the X-Files continues for people who understand such references....

This is not a post discussing some kind of geopolitical issue involving Myanmar (Burma) and the Philipines.

You see the other day, regular reader Andrew West, in a comment to my Who forgot the culture?, asked:

Completely off-topic, but I notice that you embed the sponsoring character (U+1831, MONGOLIAN LETTER SHA) in an html font tag specifying "Mongolian Baiti" as the font face. It drives me crazy that IE7 (like IE6 before it) lists Mongolian as a "language script" that you can configure the font for, but it will not populate the font lists with any fonts regardless of how many fonts you have on the system that support Mongolian (including Mongolian Baiti), so it is impossible to actually configure what Mongolian font to use! The good news is that it does display Mongolian using Mongolian Baiti without explicitly specifying the font in the html, but the bad news is that I can't get it to use a Mongolian font other Mongolian Baiti without messing with the html. I just wish someone would fix IE ... or is this one of those Kafkaesque examples like Uyghur where Microsoft can't fix something, however broken, in case it breaks user expectations?

I suspected that I knew what was going on here, but it was really worthy of its own blog and I wasn't sure how quickly I'd get to it so I recommended he put a note in the Suggestion Box just in case it wasn't going to be quick....

Which he did:

I know I'm not going to like the answer, but can you explain how the font configuration dialog in Internet Explorer works, in particular the behaviour for Mongolian (font list is never populated) and Myanmar (font list is populated with fonts that cover Tagalog, but none that cover Myanmar)?

Then I had to cancel the blog that was happening for this slot and I ended up deciding to do it right away instead....

Andrew is right that he probably won't like the answer, but it is something that is fixable, an even technically work-aroundable if a font author is willing to do something that hr or she would ordinarily consider to be very stupid. :-)

Perhaps I should explain.

We'll start in the Tools|Internet Options... Fonts... dialog:

(I guess I have no Tagalog fonts!)

and for good measure we'll include one that has some fonts in it:

Now in the end the information on actual selections is stored in the registry, under

    HKCU\Software\Microsoft\Internet Explorer\International\Scripts

which is clearly an Internet Explorer settings key with SCRIPT ID values 36 (Myanmar) and 39 (Mongolian):

But for the list of potential fonts, that is not IE at all; that is MLang.

Now I blogged this a bit over two years ago in Where are the IE plain text fonts?, and in that blog I mentioned:

Now the actual population of the two lists is happening via MLang, and as Paul points out you could think of the list on the left as being for proportional fonts and the list on the right as being for fixed pitch (monowidth) fonts.

MLang goes through a two step process that I will get into in another post, coming soon. :-)

And since I never did get back to it, I guess Andrew has proof that things often get lost if they aren't put in one of those lists like the Suggestion Box! I am actually happy to have the proof because otherwise I look kind of petty or something with my request....

Anyway, I'll explain it now -- it all works via a Trust; But Verify! mechanism.

The Trust part is where it trusts the font to describe its own Unicode ranges in its own internal FONTSIGNATURE.fsUsb bits, the Unicode Subset bits. That is step one.

The Verify part is where it does a spot check on a specific Unicode code point in th script range, to make sure that the FONTSIGNATURE is not lying. Because FONTSIGNATUREs, like men, lie. Like that bit from the movie Up the Creek an it's fictional typographical version Up the Foundry between Tim Matheson (as the font) and Jennifer Runyon (as the user):

Font: I will tell you about my coverage.
User: You wouldn't lie to me?
Font: Of course I'd lie to you, I'm a font. But I'm not lying now....

In fact, it really relies on that Verify step and perhaps even skips the Trust step a bit, sometimes?

And it spot checks the font CMAP to make sure a specific candidate character is in it.

I mentioned there was as problem here, didn't I?

Here is where the problem sits.

Deep in the heart of MLang, in its mlflink.cpp source file, it has:

• Myanmar with a candidate character of U+1700 (ᜀ, aka TAGALOG LETTER A)
• Mongolian with no candidate character given at all.

And this is why Mongolian never shows up (since it has no explicit character to check for) and Myanmar shows up when your font has Tagalog (since that is the character it looks for).

Which is the essential workaround for Myanmar -- add that one specific Tagalog character to your Burmese font? Totally obnoxious, but until/unless someone fixes MLang....

Let's put all the values in a table so you can see them:

You can probably see the other problem here -- all of the scripts that are missing; perhaps the fix needs to be a bit more than just the two broken ones, in the long run....

Speaking of which -- any NLS testers stirring about who'd like to enter a bug on this small bundle of MLang issues that will also affect IE8 on the next version of Windows if it isn't fixed? :-)

This blog brought to you by ᜀ (U+1700, aka TAGALOG LETTER A)

# Andrew West on 18 Apr 2008 5:17 AM:

# Andrew West on 18 Apr 2008 5:39 AM:

# Michael S. Kaplan on 18 Apr 2008 5:43 AM:

# Andrew West on 18 Apr 2008 6:12 AM:

# Michael S. Kaplan on 18 Apr 2008 7:41 AM:

# John Cowan on 18 Apr 2008 1:17 PM:

# Michael S. Kaplan on 18 Apr 2008 1:26 PM:

# Andrew West on 18 Apr 2008 4:28 PM:

# Michael S. Kaplan on 18 Apr 2008 4:31 PM:

# Andrew West on 18 Apr 2008 4:40 PM:

# Okisan on 1 Sep 2008 1:50 AM:

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