han page 8 - Dave's Blog

The goal of this experiment was to combine the flipping tables emoticons with the Threw It On The Ground video using shiny new HTML5-ish features and the end result is the table flipper flipping the Threw It On the Ground video.

The table flipper emoticon is CSS before content that changes on hover. Additionally on hover a CSS transform is applied to flip the video upside down several times and move it to the right and there's a CSS transition to animate the flipping. The only issue I ran into is that (at least on Windows) Flash doesn't like to have CSS transform rotations applied to it. So to get the most out of the flip experiment you must opt-in to HTML5 video on YouTube. And of course you must use a browser that supports the various things I just mentioned, like the latest Chrome (or not yet released IE10).

I've been working on the Glitch Helperator. It is a collection of tools and things I've put together for Glitch. It has a few features that I haven't seen elsewhere including:

Favorite Streets

A notebook in which you can save information about interesting streets and later use it to find your way back to them.

Birthday

Find out how old your Glitch is and the date of your next birthday in Glitch time or Earth time.

API Update History

A history of changes to the streets, skills and achievements of Glitch noting when new ones are added and when existing ones are changed.

It also has an interactive skill tree, find nearest feature tool, and achievement display. If you play Glitch, check it out.

Elaborating on a previous brief post on the topic of Web Worker initialization race conditions, there's two important points to avoid a race condition when setting up a Worker:

1. The parent starts the communication posting to the worker.
2. The worker sets up its message handler in its first synchronous block of execution.

For example the following has no race becaues the spec guarentees that messages posted to a worker during its first synchronous block of execution will be queued and handled after that block. So the worker gets a chance to setup its onmessage handler. No race:

'parent.js':
   var worker = new Worker();
   worker.postMessage("initialize");

'worker.js':
   onmessage = function(e) {
      // ...
   }

The following has a race because there's no guarentee that the parent's onmessage handler is setup before the worker executes postMessage. Race (violates 1):

'parent.js':
   var worker = new Worker();
   worker.onmessage = function(e) {
      // ...
   };

'worker.js':
   postMessage("initialize");

The following has a race because the worker has no onmessage handler set in its first synchronous execution block and so the parent's postMessage may be sent before the worker sets its onmessage handler. Race (violates 2):

'parent.js':
   var worker = new Worker();
   worker.postMessage("initialize");

'worker.js':
   setTimeout(
      function() {
         onmessage = function(e) {
            // ...
         }
      },
      0);

Sarah and I have been enjoying Glitch for a while now. Reviews are usually positive although occasionally biting (but mostly accurate).

I enjoy Glitch as a game of exploration: exploring the game's lands with hidden and secret rooms, and exploring the games skills and game mechanics. The issue with my enjoyment coming from exploration is that after I've explored all streets and learned all skills I've got nothing left to do. But I've found that even after that I can have fun writing client side JavaScript against Glitch's web APIs making tools (I work on the Glitch Helperator) for use in Glitch. And on a semi-regular basis they add new features reviving my interest in the game itself.

As a professional URI aficionado I deal with various levels of ignorance on URI percent-encoding (aka URI encoding, or URL escaping).

Worse than the lame blog comments hating on percent-encoding is the shipping code which can do actual damage. In one very large project I won't name, I've fixed code that decodes all percent-encoded octets in a URI in order to get rid of pesky percents before calling ShellExecute. An unnamed developer with similar intent but clearly much craftier did the same thing in a loop until the string's length stopped changing. As it turns out percent-encoding serves a purpose and can't just be removed arbitrarily.

Percent-encoding exists so that one can represent data in a URI that would otherwise not be allowed or would be interpretted as a delimiter instead of data. For example, the space character (U+0020) is not allowed in a URI and so must be percent-encoded in order to appear in a URI:

1. http://example.com/the%20path/
2. http://example.com/the path/

In the above the first is a valid URI while the second is not valid since a space appears directly in the URI. Depending on the context and the code through which the wannabe URI is run one may get unexpected failure.

For an additional example, the question mark delimits the path from the query. If one wanted the question mark to appear as part of the path rather than delimit the path from the query, it must be percent-encoded:

1. http://example.com/foo%3Fbar
2. http://example.com/foo?bar

In the second, the question mark appears plainly and so delimits the path "/foo" from the query "bar". And in the first, the querstion mark is percent-encoded and so the path is "/foo%3Fbar".

Most existing DRM attempts to only allow the user to access the DRM'ed content with particular applications or with particular credentials so that if the file is shared it won't be useful to others. A better solution is to encode any of the user's horrible secrets into unique versions of the DRM'ed content so that the user won't want to share it. Entangle the users and the content provider's secrets together in one document and accordingly their interests. I call this Blackmail DRM. For an implementation it is important to point out that the user's horrible secret doesn't need to be verified as accurate, but merely verified as believable.

Apparently I need to get these blog posts written faster because only recently I read about Social DRM which is a light weight version of my idea but with a misleading name. Instead of horrible secrets, they say they'll use personal information like the user's name in the DRM'ed content. More of my thoughts stolen and before I even had a chance to think of it first!

As a professional URI aficionado I deal with various levels of ignorance on URI percent-encoding (aka URI encoding, or URL escaping). The basest ignorance is with respect to the mere existence of percent-encoding. Percents in URIs are special: they always represent the start of a percent-encoded octet. That is to say, a percent is always followed by two hex digits that represents a value between 0 and 255 and doesn't show up in a URI otherwise.

The IPv6 textual syntax for scoped addresses uses the '%' to delimit the zone ID from the rest of the address. When it came time to define how to represent scoped IPv6 addresses in URIs there were two camps: Folks who wanted to use the IPv6 format as is in the URI, and those who wanted to encode or replace the '%' with a different character. The resulting thread was more lively than what shows up on the IETF URI discussion mailing list. Ultimately we went with a percent-encoded '%' which means the percent maintains its special status and singular purpose.

Cool and (relatively) new methods on the JavaScript Array object are here in the most recent versions of your favorite browser! More about them on ECMAScript5, MSDN, the IE blog, or Mozilla's documentation. Here's the list that's got me excited:

some & every

Does your callback function return true for any (some) or all (every) of the array's elements?

filter

Filters out elements for which your callback function returns false (in a new copy of the Array).

map

Each element is replaced with the result of it run through your callback function (in a new copy of the Array).

reduce & reduceRight

Your callback is called on each element in the array in sequence (from start to finish in reduce and from finish to start in reduceRight) with the result of the previous callback call passed to the next. Reduce your array to a single value aggregated in any manner you like via your callback function.

forEach

Simply calls your callback passing in each element of your array in turn. I have vague performance concerns as compared to using a normal for loop.

indexOf & lastIndexOf

Finds the first or last (respectively) element in the array that matches the provided value via strict equality operator and returns the index of that element or -1 if there is no such element. Surprisingly, no custom comparison callback method mechanism is provided.

Last time I wrote about how I switched from Delicious to Google Reader's shared links feature only to find out that week that Google was removing the Google Reader shared links feature in favor of Google Plus social features (I'll save my Google Plus rant for another day).

Forced to find something new again, I'm now very pleased with Tumblr. Google Reader has Tumblr in its preset list of Send To sites which makes it relatively easy to add articles. And Tumblr's UX for adding things lets me easily pick a photo or video to display from the article - something which I had put together with a less convenient UX on my bespoke blogging system. For adding things outside of Google Reader I made a Tumblr accelerator to hookup to the Tumblr Add UX.

Of course they have an RSS feed which I hooked up to my blog. The only issue I had there is that when you add a link (and not a video or photo) to Tumblr, the RSS feed entry title for that link is repeated in the entry description as a link followed by a colon and then the actual description entered into Tumblr. I want my title separate so I can apply my own markup so I did a bit of parsing of the description to remove the repeated title from the description.

Shortly after joining the Internet Explorer team I got a bug from a PM on a popular Microsoft web server product that I'll leave unnamed (from now on UWS). The bug said that IE was handling empty path segments incorrectly by not removing them before resolving dotted path segments. For example UWS would do the following:

A.1. http://example.com/a/b//../
A.2. http://example.com/a/b/../
A.3. http://example.com/a/

In step 1 they are given a URI with dotted path segment and an empty path segment. In step 2 they remove the empty path segment, and in step 3 they resolve the dotted path segment. Whereas, given the same initial URI, IE would do the following:

B.1. http://example.com/a/b//../
B.2. http://example.com/a/b/

IE simply resolves the dotted path segment against the empty path segment and removes them both. So, how did I resolve this bug? As "By Design" of course!

The URI RFC allows path segments of zero length and does not assign them any special meaning. So generic user agents that intend to work on the web must not treat an empty path segment any different from a path segment with some text in it. In the case above IE is doing the correct thing.

That's the case for generic user agents, however servers may decide that a URI with an empty path segment returns the same resource as a the same URI without that empty path segment. Essentially they can decide to ignore empty path segments. Both IIS and Apache work this way and thus return the same resource for the following URIs:

http://exmaple.com/foo//bar///baz
http://example.com/foo/bar/baz

The issue for UWS is that it removes empty path segments before resolving dotted path segments. It must follow normal URI procedure before applying its own additional rules for empty path segments. Not doing that means they end up violating URI equivalency rules: URIs (A.1) and (B.2) are equivalent but UWS will not return the same resource for them.