Idle Time

Speaking of everybody’s favorite WebKit plug-in, here’s how it works. This should help you understand how it fails on some sites, and maybe aid you in contributing to its development.

First off, it is a WebKit plug-in; it’s written in Cocoa and uses WebKit’s own plug-in API. It does not use the Netscape plug-in API.

A WebKit plug-in declares a list of MIME media types in its Info.plist bundle. It does this by way of a dictionary of dictionaries:

<key>WebPluginMIMETypes</key>
<dict>
    <key>application/x-shockwave-flash</key>
    <dict>
        <key>WebPluginTypeDescription</key>
        <string>ClickToFlash</string>
    </dict>
</dict>

WebKit only loads a WebKit plug-in when it first encounters some content that it needs the plug-in for. It uses these Info.plist dictionaries to know which plug-in it needs to load. So, in the case of ClickToFlash, it only loads ClickToFlash when it encounters something that is of type application/x-shockwave-flash.

Here’s the brilliant part. Adobe’s Flash Player plug-in actually declares* two MIME media types: application/x-shockwave-flash and application/futuresplash.

You will notice that ClickToFlash only declares one of these.

As it turns out, everybody only uses application/x-shockwave-flash. ClickToFlash exploits this.

When you click on the ClickToFlash view, it modifies the object or embed element that the view represents, changing its type attribute to the other type—the one ClickToFlash doesn’t declare; the one no webpages actually use. WebKit notices this change and looks again for a plug-in to handle the movie. This time, it comes up with only one handler: the real Flash Player plug-in.

There are several reasons why a site may not work with ClickToFlash. I suspect one reason is that they try to interact with the movie via JavaScript; ClickToFlash doesn’t export a script object and wouldn’t be able to communicate with the real Flash Player anyway. The script finds itself talking to a wall, and breakage happens.

So now that you know how ClickToFlash works, maybe you can help fix its bugs?

* Flash Player doesn’t declare its MIME types in its Info.plist; it declares them in a resource file, in ‘STR#’ resource 128. Thanks to WebKit developer Mark Rowe for reminding me to look for a resource. ↶

I normally hate the advertisement apps that several companies have created for the iPhone, but in this case, I’ll make an exception.

The newest advertisement app is the one for Death Cab for Cutie. As you can guess, it’s free.

The reason I like this one is because it actually includes ten (as of 1.0—eight as of 1.1) DCfC songs at medium quality (AAC, 96 kbps). Good enough for me—certainly good enough for free.

You don’t need an iPhone to use this app. You can easily extract the music from the app bundle and then dispose of what’s left.

After downloading the app, here’s what you have to do.

1. Switch to the Applications section of iTunes.

2. Right-click on the DCfC app and click Show in Finder.

   

3. You’ll see the .ipa file. Open this in an unzipper application such as Archive Utility, StuffIt Expander, or BetterZip. (BetterZip will let you go straight to the .app bundle, so you should use that if you have it.)

   

4. In the unzipped folder, find the actual app bundle. (It’ll have a prohibitory sign on it because it’s an iPhone app.)

   

   Right-click on it, then choose Show Package Contents.

5. You haven’t far to look, since iPhone apps are old-style flat bundles, not new-style hierarchical bundles.

   In version 1.0, the m4a files were right there. Since version 1.1, they’re not; the app streams them on demand. Open the media.stream.xml file in your favorite text editor, copy each http://[…].m4a URL, and paste it into your browser’s Downloads window.

6. If you don’t want any of the other features of the app (e.g., its discography or tour dates), delete the app in iTunes.

If you enjoy filling out the Lyrics tab in iTunes and reading along in TuneTagger, you may also want to write a program to read the discography.xml file (also in the app bundle) and copy the lyrics into iTunes. If you write such a program, feel free to link to it in a comment.

UPDATE 2009-02-06: Updated instructions for version 1.1, wherein they stopped bundling the .m4a files in the application.

The WebKit plug-in ClickToFlash has been an instant hit over the past 24 hours. The original version was on a Google Code project, but that project is now closed to the public. Before the Google Code project went 0600, Jonathan Rentzsch set up a fork on GitHub to gather changes submitted by Gus Mueller and Jean-François Roy.

Unfortunately, both the original and Rentzsch’s current version have one immediately-noticeable deficiency: In place of the Flash movie, the plug-in displays only a blank gray gradient background. It’s easy to think that there’s simply nothing there, or that the page is not done loading.

I decided to solve the problem myself. I forked the fork and posted my own version (along with a binary installer).

My interpretation of the plug-in adds three features:

1. Swap in the Flash movie on mouse-up, not mouse-down. This gives you a chance to back out by moving the mouse out of the view.
2. Invert the gradient when the mouse is down. This makes the view look (as well as act) more like a button.
3. Fixes the blank-background problem. A number of people have done this in other forks, but I think my solution is best:

My solution has two advantages:

• Its drawing is fully vector-based, which means that that it will scale to fit the would-be movie’s area and will look good no matter how big the would-be movie is.
• I designed the implementation so that you can replace it with different drawing code if you’d prefer a different click-to-play symbol.

The original, Jonathan Rentzsch’s fork, and my fork are all under the MIT license. And, of course, he is welcome to pull my changes upstream.

The most popular mix-and-match-music app, according to the completely objective score of how often I hear its name, is Pandora.

Most of this popularity came with their release of an iPhone app back in July 2008. The iPhone app makes the site portable: previously, you could only listen to Pandora while chained to a browser (or a SSB), but now you can listen to it anywhere that’s in cell range.

Pandora now has competition.

It first appeared in AppShopper’s free iPhone apps feed on 2008-11-08, but I didn’t see it then (I probably scrolled past it). I did see it when they released their 1.1.3 update back on 2008-11-31.

Its name is Finetune. Like Pandora, it’s free.

The differences:

• Unlike Pandora, Finetune doesn’t require an account.
• Pandora has an option to jump over to the iTunes Store to buy a song; Finetune has no such feature.
• Finetune only creates stations based on artists; Pandora lets you name an artist, song, album, or composer.

I think Finetune does a slightly better job of selecting songs that are similar to the work of the requested artist. (Sometimes this is hard, as in the case of the Beatles, who produced very diverse work.)

One major drawback to Finetune is that, since it only lets you select based on artist (performer), not composer, it really sucks for classical music. (The service has it, but it’s little better than shuffle-play.) If you want a customized classical station, Pandora is currently your only option.

(Note: I wrote this before Pandora 2.0 came out, but it’s still accurate. If anything, Pandora 2.0 is even better for classical now, since you can now make stations by genre.)

On 2008-12-12, Tim Haines, the developer of BurnBall, contacted me on Twitter to offer me a free promo code. I accepted, and played the game on my first-generation iPod touch.

The game is basically Qix with a Sonic-the-Hedgehog-esque theme. Based on that, I give you this pull-quote:

If you like Qix, you’ll like BurnBall.

As it happens, I don’t like Qix. The main thing about Qix that frustrates me is that enemies can kill you just by touching your trail while you’re cutting off another piece of the level. This makes some sense for the Tron-based theme of some of the other Qix work-alike games, but it has the effect on gameplay that you can’t make any but incremental progress, especially after the first few levels, as the number of enemies goes above 2. Your only hope is that your enemies will see some shiny thing and leave you alone long enough to let you complete your wall; otherwise, you can only complete the level a little bit at a time.

One way in which somebody could improve Qix would be to let enemies go right through your wall, and compensate by making them more aggressively pursue you. Then, you’d stand a reasonable chance of completing the wall, if you can just dodge the enemies. Another way would be to have enemies bounce off the wall, which would provide you with a way to restrain them while you draw more wall—but that may make the game too easy.

BurnBall is graphically different enough from Qix that it could pull off either change, although it probably should be an alternate game mode.

So, basically, the only reason I dislike BurnBall is because I dislike Qix games in general.

That said, BurnBall is a very good Qix game, being both well-drawn and responsive to your control. (Since I originally drafted this post, there’s been an update that tweaked the tilt response; I haven’t tested it.)

BurnBall has an advantage over Qix work-alikes on other platforms, in that you can move in any direction—you’re not limited to up, down, left, and right. You move by tilting the iPhone.

Another advantage of BurnBall over other Qix work-alikes is that Haines holds high-score competitions with monetary prizes on the app’s Facebook page. He also posts a free promo code every time that page gets another 100 subscribers, so you may not even have to buy the game.

If you’d rather not wait for the next promo code, the app is 99¢ on iTunes.

One of the ongoing debates among users of iPhone OS devices is whether an app’s settings belong in the app itself, or the Settings app.

I’m of the opinion that this wouldn’t even be a debate if it weren’t for Apple’s prescription in the iPhone HIG that every iPhone app’s settings should be in the Settings app. Mac apps don’t come with prefpanes for their preferences (with the exception of faceless background apps like Growl). Windows apps don’t, either, that I know of. GNOME and KDE apps don’t pollute Ubuntu’s Control Panel.

The iPhone is the only OS I know of whose developer recommends that app developers put their application settings in the system-wide Settings app.

As we’ve seen several times on every platform, it’s OK to break one of the local Human Interface Guidelines if and only if the violation makes the interface better.

I think this guideline is one that iPhone developers should violate flagrantly.

But there’s a problem. The iPhone doesn’t really have an icon for a Settings button. Most developers seem to use the icon that one of the frameworks apparently provides, but this isn’t the proper use of that icon. The means info, not application settings.

Another choice is the gear icon for Action buttons:

But, again, we have a conflation of functions. The button in question is not an Action button; it is a Settings button. This icon is not a Settings icon. (I suspect that most people who use the Action icon use it because it doesn’t have any particular association with “action”, either, other than Apple’s endorsement of it for that.)

The Iconfactory, wisely, chose differently in Twitterrific. I suspect that this was largely coincidence, as the Mac version of Twitterrific came first and already had a Settings icon; for the iPhone version, the developers simply used the same icon. It works well enough:

But it’s not perfect. A wrench does not say “settings”. (I offer myself as evidence: When I first saw it in the Mac version, I didn’t know it was the Preferences button.) Generally, a wrench means “edit this”, as in the context of a game.

What we need is an icon that says “settings”. Ideally, this icon should either convey the notion of a changeable state value (as the previously-favored light switch [Mac OS X through Tiger] and slider [Mac OS] did), or build on an existing association with the concept of settings.

Let’s go with the latter. I nominate the Settings app’s icon:

Familiar enough, wouldn’t you say?

That’s Apple’s version. Here’s my button-icon (a.k.a. template) version, in the 16-px size:

I tried it out in the iPhone version of Twitterrific on my iPod touch. Before and a mock-up of after:

After I created this icon, I wondered what it would look like in the Mac version of Twitterrific.

Here’s the original:

… And right away we have a problem. These buttons are already framed; my white frame will glare here.

Fortunately, that’s easy to solve. With ten seconds of work, I created a frameless version. Here’s what that looks like:

I think we could all get used to this icon. This wouldn’t have worked at all before Apple changed the icon of System Preferences to match the iPhone Settings app, but now it can.

I don’t think it’s perfect. Perhaps a real icon designer (I’m just a programmer) can refine it. But I think it’s a good first draft. I’m curious to hear your opinions; please post constructive feedback in the comments.

If you want to use this icon, go ahead. Here’s the original Opacity document , from which you can build all the many variations of the icon. (Click on Inspector, then Factories, then find the version you want in the list and click its Build button.)

notify(3) is a simple API that allows processes to poke other processes, and to be poked.

The API is similar to NSDistributedNotificationCenter, except that it’s not object-oriented, it’s not based on Foundation or CF, and it doesn’t allow you to attach a property list to the notification.

You register in one of four ways:

notify_register_check

Sign up under a name, and get a registration token.

notify_register_signal

Have the system send your process a signal when another process posts a notification with a particular name. Also get a registration token.

notify_register_mach_port

Have the system send your process a message on a Mach port when another process posts a notification with a particular name. Also get a registration token.

notify_register_file_descriptor

Get a registration token, and have the system write that token to a file descriptor when another process posts a notification with a particular name.

Each of the last two functions will create the Mach port or file descriptor for you, unless you tell it to use one you already have. You do that by passing NOTIFY_REUSE.

All four functions give you a registration token (the first one does nothing else), which is simply a signed 32-bit integer. You can then use notify_check to poll that token to see whether any processes have posted a notification to it since the last time you checked. (I don’t know how the other notification methods affect this—e.g., whether notify_check will ever return true if you got the token from notify_register_signal.)

You free the token using notify_cancel. This also closes any Mach ports or file descriptors you have associated with it. There is no way to disassociate them from the token or to cancel the token without closing the associated resources.

On the sending side, the API provides one function: notify_post. It takes one argument, which is the notification name; this is the same name that any receiving processes passed to their chosen notify_register_whatever function.

Leopard adds a new feature: you can associate a shared 64-bit number with a name using notify_set_state, and retrieve that number using notify_get_state. I suggest that you only use notify_set_state in a single process, as I can imagine race conditions occurring if two processes try to set state under the same name. If you need bidirectional communication, use two notification names (or a different means of communication, such as sockets or Mach ports).

Apple introduced the rest of the notify(3) API in Panther.

By which I mean, sources that you can check periodically or subscribe to to receive a steady stream of free music.

For music podcasts, use a regular RSS reader (or a dedicated podcatcher, if you have one), not iTunes. I’ve had problems convincing iTunes to accept files into its Music library that I’d downloaded through its podcatcher.

• Free stuff on iTunes: Three songs, one music video, zero or more (usually zero) audiobook excerpts, and zero or more (usually more) episodes of TV shows every week.

• Free stuff on Amazon: As of this writing, 665 songs (once over 3000). At least one new song every week.

• eMusic’s Daily Download (podcast feed) is available to the public. That was a pleasant surprise; I commend eMusic for it. (Added 2008-12-09)

• The Current’s Song of the Day podcast: One song per weekday from Minnesota Public Radio’s station The Current.

• Deutsche-Welle’s Beethoven podcast: Not just Beethoven; it includes other composers’ works, as well. Generally updates once a year.

• Deutsche-Welle’s Classical Masterpieces podcast: This one only ran for a limited time, but the feed is still available. My suggestion: Subscribe, grab everything, then unsubscribe.

• Mercedes-Benz Mixed Tape: A new round of 10 tracks every 8 weeks. The webpage is a Flash app, but there is an “MP3 Download” button that serves up a zip archive. (UPDATE 2008-12-09: Here’s their feed. The item you want is labeled “MP3 Download”. No enclosures; you’ll need to go to the webpage.)

• Triple J, a radio station in Australia. Appears to be mostly rock/pop. No fixed interval, but they do have a podcast feed. Thanks to Matt for suggesting it in a comment.

• KEXP has a Song of the Day podcast (podcast feed), which is weekdaily. As of this writing, there are 637 songs in the archive. Caution: Not all the songs are tagged, so you may have to do some tag repair.

• McGuinn’s Folk Den (podcast feed), wherein Roger McGuinn records and posts one folk song a month. You’ll need to tag the files yourself. Thanks to Jesse for suggesting it in a comment.

• Stereogum runs one song (sometimes two) per weekday. They have a dedicated section for these MP3s (podcast feed), including monthly zip archives of all the MP3s back to December 2006, available by direct download or BitTorrent. (Added 2008-12-17)

• MBV is a network of several MP3 blogs: Said the Gramophone, Fluxblog, Largehearted Boy, The Catbirdseat, and Chromewaves. The MBV site aggregates the member sites. (Added 2008-12-17; thanks to Colin for suggesting Said the Gramophone on Twitter)

• Largehearted Boy is one of the MBV sites, but one thing you don’t get in the MBV feed is the Daily Downloads posts. These are chock-full of up to a dozen free songs each day, all direct from the labels and promotion firms (so, all legal). The Daily Downloads also usually include tapings of live shows, either hosted on the Internet Archive or distributed via BitTorrent.

• NME is a music news website and magazine based in the UK. One of the website’s departments is The Daily Download (podcast feed).

• Spinner is AOL’s music blog. Unlike most of these, it doesn’t have a dedicated daily-download feed, but thanks to Yahoo! Pipes, I was able to make such a feed.

• Greg Hewgill maintains a list of torrents of music from the South-by-Southwest (SXSW) conference. He hosts most of these himself, but Ben Stolt is running the 2009 torrent. All of the torrents consist of music from the SXSW website.

  The music from 2009 is the largest serving yet: 1,265 files weighing a total of 6.15 GiB, divided among three torrents. For reference, that’s more songs than are in the first 2+¼ years of Stereogum’s MP3 archive.

These are some sites that I don’t personally subscribe to, but am aware of and occasionally benefit from indirectly (e.g., when Largehearted Boy posts a link to a Team Love track):

• A site called RCRD LBL has a blog called RCRD SELECTOR, which provides a few free songs per day. The feed doesn’t use enclosure tags, which makes podcatching difficult, but I’m listing it anyway in case you’re OK with that.

• You Ain’t No Picasso is primarily a music blog, although it has the occasional non-music-related post. Not every post has MP3s on it, but most do. Has a feed, but no enclosure tags. (Added 2008-12-17; thanks to Mike Krieger for linking to one of their posts on Twitter, and Colin for retweeting that link)

• The Hype Machine aggregates a lot of MP3 blogs, including the aforementioned Stereogum. Has a feed, but no enclosure tags. (Added 2008-12-17; thanks to Colin for suggesting it on Twitter)

• Team Love is a record label that gives away songs on their Library page. There’s no dedicated Library feed, so you’ll have to check back periodically (Tuesdays?).

  One thing you’ll notice is that the front page says in one paragraph that the Library is “open to the public 24/7”, and then in the next paragraph that you’ll need to open an account. There is some open-to-the-public access on the right side of the page (“Artists” and “Featured MP3s”); I don’t know what an account gets you.

  Added 2008-12-17. Thanks to Matt Morrell, who is a musician himself (with at least one song of his own available for free) and sent me the link on Twitter.

• KRCW’s Today’s Top Tune podcast is another weekdaily rock-music podcast (with, of course, a a podcast feed). Note that not every episode is a song; for example, right now, the oldest of the three episodes in the feed is an interview with Tony Hawk. Note also that the song files have borked tags, with the artist in the title tag and the song title nowhere; you’ll have to fix these yourself.

  KCRW has other shows, but it looks like Today’s Top Tune is the only one you can stock your music library from. (Corrections welcome.)

  Thanks to Steven for linking to Today’s Top Tune in a comment.

If you know of other, similar sources, I invite you to link to them in the comments.

UPDATE 2009-03-26: Segregated sites I don’t subscribe to into their own list, and added Largehearted Boy, NME, and Spinner.
UPDATE 2009-04-06: Demoted KCRW to the sources-I-don’t-subscribe-to list. I get enough music from other sources now that I don’t care about it enough to deal with its broken tagging scheme.

afconvert is a command-line utility that uses Core Audio to convert audio files from one format to another.

The manpage is actually pretty sparse (like the rest of the Core Audio documentation); you’re better off reading the command-line help:

% afconvert -h

A simple example is to convert an AIFF file to AAC in an MPEG-4 file:

% afconvert -f 'm4af' -d 'aac ' -b 98304 Recording.aiff

The resulting file is 96 kbps (98,304 bps) and is named “Recording.m4a”.

UPDATE 2008-11-26: Corrected permalink and title to include the section number.

Some explanation:

• Kind does not contain URL: Excludes streams
• Kind does not contain ideo: Excludes music videos
• Genre does not contain Comedy or Spoken Word: Excludes anything that isn’t actually music

Here are some types of apps that I’m tired of seeing over and over again on the iPhone App Store. In some of these categories, I’ve picked a winner that completely solves the problem; you’re welcome to nominate winners for the others.

• Flashlight (solution: myLite)
• Tip calculator (solution: Calculator—seriously, is subtotal × 0.2 so damn hard?)
• Any app with a checkmark icon, regardless of function: Think of a different icon, please. At this point, you might as well just make the word “app” your icon.
• App to help you find your way back to your parked car: The main problem is that all of these use Core Location rather than just tracking movement through the accelerometer. That makes the app useless if you don’t have an iPhone 3G and you’re out of cell range or don’t have a cell antenna (iPod touch).
• One-tap contact dialer (also includes 911/999 dialers)
• Apps that fake receiving a phone call
• Fortune-telling/decision-making apps
• The Puzzle desk accessory
• Sudoku (solution: ACTSudoku and its free light version)

There’s nothing wrong with competition, but these are saturated markets. If you’re not going to solve the problem in a completely different way (e.g., by not using Core Location to set the location of the parked car), then don’t waste your time—write something else.

If you have any suggestions for other categories that should go on the list, feel free to leave a comment.

New series: Manpage FridayMonday. Every Fridayother Monday, I will post a link to one manpage that comes with Mac OS X. [See update below.]

Today, it’s backtrace(3), which tells you about three functions:

SYNOPSIS

#include <execinfo.h>

int
backtrace(void** array, int size);

char**
backtrace_symbols(void* const* array, int size);

void
backtrace_symbols_fd(void* const* array, int size, int fd);

DESCRIPTION

These routines provide a mechanism to examine the current thread’s call stack.

backtrace() writes the function return addresses of the current call stack to the array of pointers referenced by array. At most, size pointers are written. The number of pointers actually written to array is returned.

backtrace_symbols() attempts to transform a call stack obtained by backtrace() into an array of human-readable strings using dladdr(). The array of strings returned has size elements. It is allocated using malloc() and should be released using free(). There is no need to free the individual strings in the array.

backtrace_symbols_fd() performs the same operation as backtrace_symbols(), but the resulting strings are immediately written to the file descriptor fd, and are not returned.

Posted in C, Documentation, Mac OS X, Manpage Monday, Programming | 3 Comments »