Phil Hassey - game dev blog
Phil Hassey as Snidely Whiplash
"You can't buy awesomeness.
You're born that way."

Adding Retina / Multitasking support to my iOS apps

Today I felt it was about time I got around to updating my Galcon apps with proper 4.x support now that everyone has it.

Adding retina is pretty easy. In EAGLView.m I had to add this snippet into initWithCoder:

	float scale = 1;
        if([[UIScreen mainScreen] respondsToSelector:
             if([self respondsToSelector:
                     scale = [[UIScreen mainScreen] scale];
                      self.contentScaleFactor = scale;

Then in my code anywhere where the scale matters, I use that information to sort things out. I found that adding retina Icons, startup graphics, and other in-game graphics was as easy as adding an extra file: Icon.png becomes Icon@2x.png, my_game_stuff.png becomes my_game_stuff@2x.png, etc. It was pretty simple. Fonts were a bit more complex because I have different font data for each sized font, so I use the scale information I discovered earlier to ensure that I use entirely different font images, instead of using the @2x trick. The one goofy bit was importing to subversion. It doesn’t work, unless you put a trailing @ at the end of the filename, since subversion treats @ as the version identifier.

Doesn't work:
svn add Icon@2x.png

svn add Icon@2x.png@

Multitasking was even easier. In my AppDelegate.m I added these methods:

- (void)applicationDidEnterBackground:(UIApplication *)application

    Event e; e.type = EVT_SUSPEND;
    [glView stopAnimation];

- (void)applicationWillEnterForeground:(UIApplication *)application
    Event e; e.type = EVT_RESUME;
    [glView startAnimation];

The first is called when the app is suspended, the second is called when the app resumes. The iOS handles saving / restoring all the texture data, so really I didn’t have to do anything. The only catch was I had to add in the glView stop/start calls to ensure that no GL calls were made while the app was suspending. The app will crash if any GL calls are made while in the background.

I do not do any background work to keep the network alive. This seems sensible because it makes it so the game will timeout after 30 seconds but you’ll still be connected if you get back sooner than that. Anything fancier could keep a player on the network indefinitely even if they are really gone. This gives the user at least a momentary opportunity to duck away and check something then resume playing.


6 Responses to “Adding Retina / Multitasking support to my iOS apps”

  1. Jason Maas Says:

    Awesome, I’m looking forward to the high-res graphics!

  2. medeman Says:

    Well, basically AWESOME!

    But you should have used the task completion API (which works for 10 minutes) for multitasking to keep the connection up…

  3. Zelkata Says:

    Explain step by step how to add multitasking and retina support… Pls do I have to use ifile or smt else?

  4. Byron Says:

    I love how iOS handles save/restore on texture data etc. On android it all gets blown away and makes it pretty tricky to have to restore/reload all your texture data.

  5. medeman Says:

    @Zelkata Phil will submit the update somewhen to the AppStore. Just download the update from there when it arrives.

  6. mac scan Says:

    Yeah, I was also looking for a more in depth guide to add multitasking support, but this gives a good start.