2014 projects

my barebones background app

my background noise app

It’s been a while since I posted an actual project I’m working on. Since I started working full time for Apportable, I’ll admit there is less time to work on projects, but that’s really no excuse. In addition, as the new year merits such reflection, I’ve been thinking about why I didn’t ship anything last year.

Then I realized, I *technically* shiped something. I shipped my children’s note teaching app (that was already on iOS) on google play using the Apportable framework. Apportable lets you compile your objective-C iOS project to android and run natively. I thought it was lies and insane when I first heard about it; now I can confirm that it is simply black magic. Anyway, I’m usually working on other company’s apps, and improving the Apportable platform where it is is not perfect, so this was a nice way to hit two birds with one stone.

I also started on a binaural beats app, and got a quick prototype, but it didn’t seem as useful or original enough to publish without specific controls, so I’m still working on that. Instead, I put my efforts into a ‘background noise’ app. I started on this because I wanted to be able to drown out the sounds of the 580 and BART that my midcentury apartment building windows are not rude enough to prevent passage into my bedroom. It’s made me remember how much I love the sample synthesis for-loop in an audio callback. (I want to post more on various synthesis techniques in the future). So far the app only has three background noises – rain, waves, and crossfaded white noise. To stay productive, I might just release it as such and develop further as my interest stays with it. To the right is a screenshot of the minimal gl/coregraphics based rendering to accompany the background noise. I’ll try and do a live coding screencast just to get some of it on the screen again.

With the full time job, I can work on all those financially-worthless-but-fun ideas that are musing around in my head that were out of the question when I was doing the solo contract-dev shop. Just to be clear, I am posting this so that I will feel embarrassed if I don’t take advantage of that freedom when I come back and check on this blog.

i used to be a programmer


Yesterday I was at Owl & Company over on Piedmont Ave in Oakland and came across an interesting read by complete chance. It is a book of poetry and narrative of archy, who was a roach in 1920, and before that, a free verse poet. Archy hops from key to key on a typewriter leaving notes for his human ‘boss’ who owns the typewritter and ‘provides’ him with food in the garbage can. It is a real treat, and because of the whitespace, a real short treat at that. I finished it within a couple hours. The curious thing was that soon after reading this I found an untitled document open on TextEdit that I do not recall having anything to do with. I’m keeping it here so that I can document it.

i used to be a programmer
but now i am just a roach that had my soul transmigrated from
a programmer after i died
why a roach you ask well if you must know
it is for my programmer sins like
using so much indirection and so many underscores
oh the irony
i can t even press the shift key being a roach
can t even make an underscore much less
left parenthesis right parenthesis

the funny thing is
being a roach now
i have many ideas
but can t code any more left parenthesis
i had some ideas while human
they all made money
like the one to drive cars
with mustaches or umlauts
can t remember same thing really
they all take thirty percent right parenthesis

when you die and turn into a roach
they give you all your money
it carries over so to say
but as a roach it is hard to pick up
a dollar bill and
they don t make credit cards for us
but now i have no rent to worry about
i live in a lovely victorian
and the food is good as ever

now i have time to think
come up with some real good ones
but since money doesn t mean anything now
i think of programs to make abstract art
i described it to the venture capitalist
he said people don t want roach art apps
they hate things that are ugly and free
or maybe just things that are free that are made by a roach
i told him i don t need money
he said why dont you need money
i said i m a roach
he said lol i should have known
i am hiring a taskrabbit to step on you
and another to save you to make it a fair game
because they call me an angel investor
and i want to disrupt the world
anyway i decided to leave then

only a few problems for roaches
there is a programmer rat here named steve
code reviewing my text
bad indentation he says
its not even code i say
he says you got that right
what a jerk


Here’s my .emacs file in all its unedited glory. May it be a light in your time of google searching or a darkness in your time of trying to understand how to configure emacs.

It’s also in a gist.

It’s a franken.emacs from lots of sources on the net. I’ve forgot them all, but almost none of this functionality originated with me and thus you should give your thanks to the anonymous internet. I wanted to document it for a while because it’s helpful when I switch to a new computer. It’s so messy that I put off documenting it. I’ve decided to share it anyways.
Features are

  • ctrl-x ctrl-o to switch between a .m, .mm, .c, .cpp file to corresponding .h file if it is nearby
  • ctrl-arrow to switch between multiple buffers/windows that you split horizontally or vertically (e.g. with ‘ctrl-x ctrl-3’
  • auto reverts when file changes on disk (e.g. when you git checkout) – note this can be a little dangerous, but I believe it doesn’t do this if you have local modifications
  • copy and paste works with os-x clipboard and vice-versa with your yank/copy/kill ring
  • other stuff

Namespacing a framework in objective-c, @compatibility_alias, and #defines

Shakespeare said something about roses and names smelling nice, but if you’re Outkast you know that sometimes, roses really smell like poo. Additionally, if you’re a programmer, you sometimes need to get another set of better spelling roses to set the world right. Far-fetched metaphors aside, namespacing issues come up less than I would expect. For one, most people know better than to call their classes ‘Object’, and everyone has their own novel solutions to the problem – be it prefixing every class with their initials or a swear word. This week I came across a project that required two implementations of the same framework to be present in the same iOS app. The frameworks had the same, or very similar headers, but the implementations were quite different. The use case in question was for migrating data from one implementation of the framework to another. Objective-C doesn’t have the namespace keyword magic that would make this problem a little faster.

My thought process evolved like this:

  1. My first thought was to rename everything in the old framework by adding a new ‘OLD’ prefix. However, this is quite a lot of work, depending on the size of the framework, and it can be tricky to come up with the right sed command that does everything you wanted.
  2. My next thought was to use #defines for everything I wanted to namespace in the headers only. However, this poses some serious problems for class naming conventions, even if you only conditionally define it within the framework compilation unit. Consider a class called ‘MyClass’. You might have MyClassDelegate, eTargetTypeMyClass, and even other classes with the same prefix or suffix, like MyClassManager or ComplicatedMyClass. #defines might or might not expand in the way you want here – but you can see the risk: it’s easy to end up with half of the file containing ComplicatedOLDMyClass in one compilation unit and OLDComplicatedMyClass in the other.
  3. 3. I found out about @compatibility_alias, which solves the problems with #2 for classes (and nothing else). However, this actually solved most of my problems and was fairly compatible with doing non-class namespacing as mentioned in 2.
  4. @interface OLDMyClass
    @protocol OLDMyProtocol
    @compatibility_alias MyClass OLDMyClass; // this tricks the MyClass.m file to use the OLDMyClass interface
    #define MyProtocol OLDMyProtocol

Limitations of @compatibility_alias:

  1. You can only use it with a real class to an aliased class. You can use it before the real class is declared (but the compiler will emit a warning). If the alias class is already declared, it will cause an error.
  2. You can only use it once per compilation unit for a given alias (you can’t use it liberally like you can with forward declares).
  3. You cannot use it with protocols, typdefs, enums, or anything besides an objective-c class.
  4. All @class MyClass forward decl’s will need to either be swapped out for an #import “MyClass.h” or changing the forward decl to @class OLDMyClass and all occurrances in the header to OLDMyClass.

So how do you namespace the protocols, typedefs, and enums? You could rename everything in the .h and .m files, but it is a lot less work to just ‘#define originalprotocol OLDoriginalprotocol’ and declare OLDProtocol in the header.

You can then #ifdef the #defines and @compatibility_alias’s on the condition that you are compiling the framework itself. This trick is similar to exporting only certain symbols when building a library, and allows for the framework’s implementation (.m files) to be remain almost entirely unchanged (using the ‘originalclass’ form), and when compiling the app, the app only sees the OLD_originalclass form, and also the #defines won’t be able to accidentally expand strings that it happens to match.

I ended up using a sed command only to change the #import to #import.

I did the above for the older version of the framework, and left the newer one unchanged. This allows them to both be used simultaneously. There are other tricks you might be able to do like dynamic loading, but if you need classes from both at the same time, this is probably the way to go.

For reference, here’s a file that I used to test the edge cases. You can compile with ‘clang -framework Foundation compatibility_alias_test.m’, or see the errors caused by wrong usage with ‘clang -DWONT_COMPILE -framework Foundation compatibility_alias_test.m’ :

#include <Foundation/Foundation.h>
#include <stdio.h>

// 1.Only classes work with @compatibility_alias:
// 2. Protocols, typedef, enums and other things are out.
// 3. You might be able to use a #define with #undef for those
// 3.1. If that would interfere with the original namespace you are colliding with,
//      you might try conditionally defining it where it is needed, probably similar
//      to exporting only some symbols when building a lib (if just including headers it would be hidden)

// forward declare of aliased name conflicts with alias
@class SpecificClass; // error: conflicting types for alias 'SpecificClass'

@protocol NonColiding_BeerHolder
@property (nonatomic, assign) int beers;
@compatibility_alias BeerHolder NonColiding_BeerHolder; // warning: cannot find interface declaration for 'NonColiding_BeerHolder'
// also, later: error: cannot find protocol declaration for 'BeerHolder'
#define BeerHolder NonColiding_BeerHolder

@interface NonColiding_SpecificClass : NSObject <BeerHolder>
@property (nonatomic, assign) int beers;

@implementation NonColiding_SpecificClass
- (id)initWithBeers:(int)beers
    if ((self = [super init])) {
        self.beers = beers;
    return self;

@compatibility_alias SpecificClass NonColiding_SpecificClass;

// you also can't double up on compatibility_alias like you can with forward decls.
@compatibility_alias SpecificClass NonColiding_SpecificClass;

int main(int argc, const char* argv[])
    SpecificClass* bob = [[SpecificClass alloc] initWithBeers:5];
    NSObject<BeerHolder>* bh = bob;

    // sanity
    printf("yo dog i'm bob and i have %d beers.\n", bob.beers);
    printf("yo dog i'm a beer holder and i have %d beers.\n", bh.beers);
    [bob release];

Mac Dictionary Services API Tease

Basic lookup working

I am a big fan of Dictionary.app. It’s pretty handy for English, but what makes it really shine is that it has a zomg-amazing Japanese dict called Daijisen. What’s more, with 10.8 Apple threw in German, French, Spanish, and Chinese dictionaries as well. However, after getting used to the app, while still using it, I have decided that it sucks. I should clarify. The dictionary content that it has is great. But the app itself is lacking some features that would make it so much more useful. I want search history that goes beyond a single app launch, and an interface for seeing what words I looked up when. I want to be able to export this list so I can make flash cards. I also want to be able to search by words other than by a ‘starts-with’ scheme, such as ‘contains’ or ‘ends with’, like many online dictionaries have.

For a while I just assumed there was no easy way of using the content the mac dictionary app uses. Then I found out about the mac dictionary services API, which looks promising at a glance.

I created the basic lookup pretty quickly while on the BART commute to work and back. But it became apparent after some tinkering that the existing API (which has only two functions for word lookup) is entirely incomplete. You can look up a string, and get a definition back from the same dictionaries that Dictionary.app uses. However, you can’t specify which dictionary, or which entry within a dictionary (e.g. for a word that has multiple definitions). This means you only will the first entry of the first dictionary that gets hit. So I decided to spend a good part of today trying to see what could be done about this.

I came across one or two or three interesting posts that showed some private API off. Most of these were for simple CLI programs, or for building their own dictionary. And used private calls such as DCSRecordCopyData() and DCSCopyAvailableDictionaries(). DCSCopyAvailableDictionaries allowed me to access specific dictionaries, and used in conjunction with DCSGetTermRangeInString and DCSCopyRecordsForSearchString, I was able to generate a reasonable list of candidate DCSRecordRefs entries from a single input word. The only thing missing was the definitions for each DCSRecordRef.

I wanted to make this dictionary for my Japanese studies. In Japanese, there are tons of homonym and homophones depending on if you use write the word with kanji or not. I didn’t see a function from my googles that would show the word listing, but doing an NSLog(@”%@”, record) on an example search for ‘いる’ showed some info about the DCSRecord structure:

lldb output:
{key = いる, headword = いる【射る】, bodyID = 111081}
{key = いる, headword = いる【要る】, bodyID = 104584}
{key = いる, headword = いる【居る】, bodyID = 163639}

It looked like the ‘bodyID’ or ‘headword’ field of DCSRecordRef had the most specific information about the result. So I went into the framework and searched for symbols of functions that might do the trick:

cd /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/DictionaryServices.framework
nm -gU DictionaryServices|grep DCS
0000000000007b06 T _DCSActivateDictionaryPanel
000000000000914d T _DCSCopyActiveDictionaries
000000000000916f T _DCSCopyAvailableDictionaries
0000000000007e07 T _DCSRecordCopyData
0000000000007e1e T _DCSRecordCopyDataURL
0000000000007e63 T _DCSRecordGetAnchor
00000000000076ef T _DCSRecordGetAssociatedObj
0000000000007e4c T _DCSRecordGetDictionary
0000000000007ebd T _DCSRecordGetHeadword
0000000000007e91 T _DCSRecordGetRawHeadword
0000000000007f04 T _DCSRecordGetString
0000000000007e35 T _DCSRecordGetSubDictionary
0000000000007e7a T _DCSRecordGetTitle
0000000000009181 T _DCSRecordGetTypeID
00000000000076d9 T _DCSRecordSetAssociatedObj
0000000000007ea8 T _DCSRecordSetHeadword
000000000000878a T _DCSSearchSessionCreate

The second entry for 棺 should be ひつぎ

There were about a 100 or so symbols or so that Apple didn’t feel like sharing via docs. I tried a few combinations, but it looks like DCSRecordGetTitle or DCSRecordGetRawHeadword produced the best strings for use with DCSCopyTextDefinition. This solves the homonym problem for the most part. However, this did not work at all with heteronyms (words that are spelled the same, but pronounced differently), since the headword/display title would be the same. For example, for the input 棺 I need the definitions for both 棺 read as ‘kan’ and 棺 read as ‘hitsugi’, but this method would give me two definitions for ‘kan’ instead. Eventually I gave up. I hope someone else figures this out. I put the intermediate result up on github. Let me know if you make any progress.

On iOS it goes without saying that you should probably avoid using private APIs, since the main means of distribution is through apple. On the mac distributing an app yourself is still viable, and thus you can use private APIs to your heart’s content. However, because the non-documented but exported symbols do not provide function signatures, it’s pretty much just a tease unless you want to spend a lot of time to figure out what each method takes. After googling symbol names, it seems dictionary services are relatively unexplored. But I’m mostly interested in this for making my hobby dictionary that I can nerd out on and add lots of obscure features to while using the apple-provided dictionaries.