Test case with screen shots and examples.

I have submitted this as Bug 23221.

On the mailing list, people are actively trying to bring Erlang up to snuff with regards to web standards.  One of the more unfortunate choices being discussed is JSON as a data notation.  JSON, unfortunately, does not actually map to Erlang in a useful way.  Joe Armstrong has gone as far as to suggest BIFs, which are decidedly unrealistic as well as unnecessary.  My goal is to create a JSON handling library.  However, the mailing list is beginning to put momentum behind an alternative proposal which is currently presented in BIF form.

This post explains why my approach is different.  Many of the issues herein are discussed by the tabled EEP (EEP 18, “JSON BIFs” by Rickard O’Keefe), but some are not, and some of these issues are accepted when I believe they should not be.  It is my position that EEP 18 is unacceptably dangerous.  I will explain why.

This paper assumes you are familiar with Erlang and with fundamental containers (the list, the array and the key/value map).  It is very helpful, but not required, to be familiar with JSON, or JavaScript or any ECMA derived language such as ActionScript.

Premise

There’s a movement starting to use Erlang for web work.  There are several stumbling blocks to that end.  Among them are a simple primary webserver, a simple primary unicode system and a simple primary JSON manager.

The webserver problem is mostly solved: there’s the httpd module, there’s yaws, there’s mochiweb, there’s the currently unavailable work at Tobbe’s Red Hot Erlang Blog, there’s even Joe’s HTTPD tutorial.  YAWS and MochiWeb in particular get a lot of action these days.  The situation isn’t amazingly straightforward, but it’s fairly straightforward; we’re in “Good Enough” territory.  (I’m building another webserver that behaves like factor’s drop-and-go server, based on Joe’s tutorial, but that’s not for here.)

The unicode problem, however, as well as the JSON problem, are not solved.  Unfortunately, whereas the Erlang community has had the foresight to deal with complex problems in modules first then to move them to syntax later, this process seems to be failing with both JSON and Unicode.  It can be argued that some of the choices made in each process are dangerous.  This community will, by and on the whole, remember the re: module, which is being replaced now with a partially incompatible successor that takes account of limitations and problems in the prior attempt, as well as moves to a stronger RE dialect.  It is important that this ability be retained for JSON and Unicode, both of which are subtly strikingly difficult problems, and both of which are unlikely to be Gotten Right™ on their respective first attempts.

The Principle of Least Surprise

One of the most important parts of writing libraries is to not write nasty shocks into place for users.  In transcoding libraries, there is one rule that defines least surprise more powerfully than any other: round-trip translations must not lose data.  No configuration of EEP 18 can achieve this.  Indeed, it is my position that a one to one translation of JSON to Erlang terms cannot exist, and that any attempt to present a not-1:1 translation as a translation is unacceptable, in that people will expect j2e(e2j(X)) == X, and that cannot be true.  This is especially important given that the suggestion that these translations become BIFs seems to be being taken seriously; foo_to_bar(X) bifs are currently never lossy, and this would create a worrying change in the meaning of several basic naming practices.

It is of critical importance, in my opinion, that we do not provide libraries which fail round-trip conversion in either direction.  At this time, EEP 18 attempts to satisfy this clause with creation-time configurability; I will explain my stance that this is inadequate below.

Why Translation is Unclear

There are, in fact, quite a few problems that prevent 1:1 translation.  We’ll go over them one by one.

1. The notations offer different fundamental containers
   1. Erlang offers dense sequence (“tuple”, {}) and singly linked list (“list”, []) containers.  The erlang standard library offers other containers; I discuss later in this document why I’m not using them.
   2. JSON offers dense sequence (“array”, []) and key-value map (“object”, {}) containers.  That’s it.
2. The notations offer different fundamental datatypes
   1. JSON has a fundamental string type; erlang doesn’t.
   2. Erlang has atoms; JSON doesn’t.
   3. JSON has booleans and “null”; Erlang doesn’t.  For transcoding, pretending they’re atoms creates ambiguity, and is therefore unacceptable.
   4. JSON has explicit support for unicode characters in strings.  Erlang doesn’t have strings at all, but rather lists of characters (in the way that C has arrays of characters).  Those lists are context and usage defined; C++ programmers may think of this as parallel to array strings vs std::string.  Erlang currently has no concept of Unicode (though that’s another issue I’m working on as divergent from the current mailing list / EEP approach.)
   5. JSON and Erlang have very different lists of quoted terms for strings.
      1. Erlang supports embedded octal with shortening, and a bunch of semi-defunct control characters like form feed ("\f") and escape ("\e").
      2. JSON supports 16-bit Unicode character embedding.
      3. Problematically, JSON does not define whether that embedding is UTF16, UCS2 or something else.  Most software implementations assume UTF16.  This document will carefully avoid the issue, which is a serious defect in this document, and a serious defect in JSON.
   6. Erlang terms are byte-available, meaning Erlang programmers may be aware of endianness; JSON objects are not.  This suggests that the handling library needs to either make a choice about internal endianness, or needs to provide control to the user.
3. The notation for similar containers is dissimilar
4. Similar notations are similar, not identical
5. Dangerous string ambiguities

Working from http://sc.tri-bit.com/outgoing/scjson%20parser%20halp.html

I was a little bored.

So we’re going to have three libraries progressing in the immediate future, with quite a few more over time:

1. HtStub – An embeddable, zero-config, zero-behavior secure Erlang webserver
2. SC A-Star – An efficient, modular ECMAscript (flash/actionscript, javascript, jscript etc) A* implementation with support for custom grid geometries (includes algorithm tutorial)
3. TestErl – unit, regression and stochastic testing for Erlang
4. ScUtil – a fairly large list of gap filling functionality for Erlang

In the near future, I will add C++ and PHP libraries, as well as many some libraries for more obscure languages like FormulaONE, Mozart-Oz, Factor and maybe (sadly) Delphi.  I have more than 30 libraries ready for release.

All those repos are pretty empty at the moment.  That will change in coming days, and I’m sure I’ll post lots of boring little snippets here about whatever minor new thing my crap does.

Yay!

The first three I’m going to release are scutil, testerl and htstub.

• scutil is my personal utility library.  It’s a hodgepodge of semi-random stuff.  there’s a whole lot of crap down there.
• testerl is a unit/regression and stochastic testing library.  One of the main goals of testerl is to have low impact on the code it tests, which it achieves through a single module attribute and a list (syntax identical to export) of the non-exported functions that the test rig needs access to for testing.
• htstub is a socket manager and HTTP protocol implementation.  It’s not a webserver – it has no filesystem access and doesn’t know how to respond to requests – it’s more of a transparent way to handle HTTP.  htstub is useful for adding a web front end to applications.

I actually intend to release some c++, actionscript, php, javascript and delphi stuff soon too, If I Get Around To It ™; that said, now that I have SVN largely automated, it’s quite likely.

I’m already doing complex efficient randomization, API access, bulk posting, timed bulk posting, base autotagging, auto-categorization, a catalog widget, and I’m going to make sure that my stuff is compatible with the All In One SEO pack.  I’m going to provide integration points, and I’m going to provide an example integration with LightBox, or one of its relatives.  I’m going to provide voting, moderated tag suggestion and home-post permalinking.

I’ll also be writing strict, browser/version portable code without hacks.  Yay!

Please let me know what you’d want to see if there were a new image plugin coming out.

[SB digg, reddit]ICANN has announced their intent to allow the registration of new gTLDs in a repeated auction process, starting for the princely sum of $100,000 for a handful of letters.  In IRC in debate the question came up how many vanity 1st level domains (hereafter vanity 1ld) would be purchased.

[digg-reddit-me]For the purposes of competition – and there’s no money involved, I just said gambling to whore diggs and such – a vanity 1LD is defined as a gTLD which represents the name of a person, company or organization.  This means that .porn is not a vanity 1tld, even though it’ll certainly be owned by a pornographer, because it’s named for its content.  By contrast, .microsoft is a vanity 1LD, as is .billclinton (which probably won’t get bought; I’m just being thorough in definition and Bill has a good sense of humor.)  If a 1LD is assigned on basis of trademark, it’s pretty much in like Flynn.

So.  Where’s the psychicitudeness?

I predict that approximately 950 vanity 1LDs will be purchased in the first auction.  (This has the startling price tag of ninety five million dollars minimum.)

Anyone want to play The Price is Right with me?  Place your bet in comments (preferably as a trackback; this is a new domain and I could use some rank).  Whoever gives the nearest answer to the number that turns out to be correct wins.  (No price is right rules; going over isn’t different than going under.)

Incidentally, if you guys are worried I’ll edit my post after the fact, just check Internet Archive for the day before the auction.  I can’t cheat; I’m being watched by www.bigbroth.er .

Bring it.  950.

1. AllowOverride All <– this probably says “none”; fix it
2. AllowOverride All <– it’s in two different parts of httpd.conf, so fix it again
3. LoadModule somepath/mod_rewrite.so <– uncomment this, and check if the file’s actually there
   

Now, I think it’s a little impractical, and it leads to a mind-bleedingly weird syntax, but it’s actually struck me that this is a very clean, very terse format for providing something akin to uniform construction behavior when you’re dealing with multiple manufacture paths to a given object. Granted, it’d be an even bigger, even uglier hack, but still, it’d work.

Witness syntax:

function exampleF(foo, bar, baz) { … }.defaults(1, 3, 7);

Hear that crashing sound? It’s your mind, breaking. But, as much as I hate to admit it, this is one genuinely lovable hack. Bravo.

• Suppress the user interface. IE starts with most of its interface turned off, but a few things aren’t. Notable things to include are to suppress the context menu and keyboard navigation.
• There are several ways to suppress the context menu. The easiest way is to do it in the html. Add oncontextmenu=”return false;” to your <body> and the problem just goes away, and it’s easily manually overridden for specific elements later.
• Alternately, you can override the interface programmatically through IDocHostUIHandler.
• Get rid of the OnNavigate noise (the clicking sound when you hit a link.) This is harder than it should be.
• Prevent keyboard navigation. If you only ever navigate once, and then do everything else in DHTML, this isn’t an issue, because there’s nothing to go forward or back to. However, if you need to, the way to do this is to capture DWebBrowserEvents2::BeforeNavigate2() and fill its last parameter, VARIANT_BOOL*& Cancel, to true. For security reasons this can’t be done in HTML without a garish ugly dialog box confirmation.
• Prevent dragging and dropping links. Do this with BeforeNavigate2() just like keyboard navigation.
• Prevent selection. The easiest way to do that is in the HTML by adding onselectstart=”return false;” to the <body>, which is also easily overridden for child elements where appropriate. If you need it programmatically, such as a block which can be turned from and to editability, that’s in IDocHostUIHandler.
• Handle some keys directly. Particularly often, control keys, tab and f-keys need very different interpretations in applications than are the defaults in IE. Some keys can be reliably intercepted in JScript, but not all of them. For lightweight stuff, use JScript; it’ll be less painful. However, if you need real control, you need to provide an IDocHostUIHandler::TranslateAccelerator() implementation.
• Suppress the interior border. People are often surprised that they turn off the window border in IE, and yet it seems to still appear. That’s because IE’s default stylesheet puts an inset bevel on every web page. Turn that off in CSS by writing body { border: 0; }.
• Begin to embed your images and other support media as resources, and access them with the res:// protocol.
• One ugly caveat: I have never found any variation of the DirectX PNG alpha filter hack which works with res://, and I’ve looked often and at some very weird variations. It is my current belief that a PNG cannot be embedded through res:// and still be fixed for alpha. This leads to the unfortunate case of requiring at least part of your resources on disk. If anyone knows a way around this, a heads-up would be greatly appreciated.
• Set up a system to exchange messages between IE DOM/DHTML/JScript and your application. There are a bujillion ways to do this, but I tend to use a combination of intercepted element events (mostly OnClick in WebBrowserEvents Invoke,) DOM extension behaviors that allow me to call C++ directly from JScript through IDocHostUIHandler::GetExternal(), and executing scripts directly on the DOM object through IHTMLWindow2::execScript().
• Build everything in the to be inside a container; make the body itself overflow: none. This prevents several ugly re-layout quirks which we’re used to on the web but not in applications, when content gets long.
• Start the container invisible, and make the black. That way, during the lag while resources are being loaded, you have a reasonable appearance. Black flashes look correct. White flashes look broken.
• Set an onload=”HandleLoad();” function for the <body>. That way, you know when all resources are loaded, and thus when it’s safe to take the invisible clause off of the main container.
• Set the main container position:relative, to make absolute positioning of contained elements easier.
• Build your web page in as a resource, and load it through IHtmlDocument2::write(). This allows you to load a document at runtime without using about:blank (which most people use, but which causes a brief white flash before your application loads; very unprofessional looking.) You’ll need SafeArrayAccessData() and SafeArrayUnaccessData() to use write() safely. When it comes time to skin or internationalize, and when you’re dealing with a compile cycle which is just linking, you’ll thank me for this.
• Suppress dragging on links and buttons. If you don’t, people will be able to drag them outside the app and onto the desktop as shortcuts, and when followed those shortcuts will lead into your HTML page from the outside (which is, surprisingly, legal.)
• Consider compressing your executable, such as with UPX, which makes resources unreadable externally.
• Set an id on your <body>. The is considered the origin of most events which don’t have a clear origin, and that means that catching these events is a lot easier (catching by id is the most straightforward way to sort out sources.)
• Resist the urge to use runtime styles. They’re not worth the problems they cause.

That should get the new IE user through some common foibles. I’ve probably missed stuff; if you can think of something, lemme know. I do not currently know of a way to embed flash, unfortunately, without leaving available an extra file.