Monthly Archives: April 2014

Why you need the hardware to develop for mobile…

Probably the second biggest roadblock for developing mobile apps is the cost of hardware (the first, of course, is the time).  Devices are expensive and it’s tough to keep up.  My current testing livery of devices is actually quite limited.  Indeed, some of my devices are not longer supported by their manufacturers or myself.

Despite the difficulty of maintaining an adequate device livery, you need the devices for testing. In a previous post, I mentioned that I’m migrating my app from OpenGL ES 1.1 to OpenGL ES 2.0.  All of my currently-supported devices support 2.0 (and in some cases 3.0).   That sounds like things should be just fine.   Well, they don’t have the exact same graphics card or OS – which will lead to horrible surprises.

I have one older iPod Touch which on iOS 6.  Having this particular device saved my bacon for the last release of one of my apps.  It turns out that the software ran just find on all of my devices except that iPod Touch.  Talk about panic!  It wasn’t an easy fix either; it required a rewrite of a major portion of my code to work correctly.

Well, in my testing for parts of my OpenGL ES transition code, I decided to try the old iPod again… and wouldn’t you know, code I thought was working fine rendered completely wrong!  It turns out there was a bug in the OpenGL code that apparently  didn’t manifest in the newer devices or on the simulator.

Realistically, you can get away with a smaller livery of devices under some conditions.  For example, if you don’t use any low-level code and stick with the high-level user interface APIs you’re more  likely to still have a stable app on many devices.  Getting into the lower-level stuff will likely cause more problems particularly in the short run as you develop, and in the long run when devices you didn’t test start reporting issues.

Just to add to the above, I don’t count the xCode simulator as a device.  I have code that works perfectly in the simulator and does not run correctly AT ALL on any device.  After all, the simulator is actually MacOS X OS and hardware, not mobile.  As a consequence, successful rendering in the simulator will not always translate to a device.  The first time you encounter this issue it is a rude awakening.  However, it shouldn’t be a surprise since all of Apple’s OpenGL  ES debugging tools only work on devices, not the simulator.

This gets back around to why my apps have yet to be ported to Android.  I only have a couple devices that use that platform for testing out of the many MANY devices out there… it’s a tad scary…



Working on migrating AE to OpenGL ES 2.0

Now that I have a break from other duties, I’ve been working on improving AE for iOS.  One of my early design decisions I made in AE is to go with OpenGL ES 1.1.  At the time, my only iOS device did not support OpenGL 2.0, so for practicality sake, 1.1 made sense.  Furthermore, I needed some basic functionality that was stripped from OpenGL ES 2.0.  ES 2.0 was clearly unattractive… at the time…

Today, the story is different.  All of my “supported” iOS devices support OpenGL ES 2.0 and in some cases 3.0.  Yes, they still support 1.1, and it’s arguable that the practical decision is to remain on 1.1.  However, it’s only practical if I don’t add new features that call on the graphics card.  I’m also considering the path to porting the application to other platforms, such as Android and Desktops.  From this perspective, ES 1.1 looks increasingly problematic.

The kicker that’s forcing the transition is the time scale control on the bottom of the screen.  It turns out that feature is quite a difficult to display.  The time scale tends to be a memory hog and requires a great deal of code to provide full functionality.  I’ve long known that the control should be moved to OpenGL rather than using higher-level functions.  Originally, the time scale was created using simple bezier-path draw calls. In the last version, I moved the system to Apple’s layers.  That transition was meant to make the code easier to maintain.  However, it turned out, on older devices in particular, the app became crash prone because the layers took up an unexpected amount of memory.  I managed to work through this problem for a stable release, but I wasn’t happy with the situation.

Enter OpenGL ES 2.0.  Now, the time scale is not done by any means, so these comments are initial impressions.  Now that I’ve worked with it, I do regret not going with ES 2.0 from the beginning (it still wouldn’t have been possible to release the original app with ES 2.0 support since I had no hardware at the time).  ES 2.0 is clearly superior to ES 1.1.  Surprisingly, I found that while in some areas ES 2.0 requires more code, the transition from layers to ES 2.0 appears, at least in some areas, is thinning out my code.  That’s exciting!  Since the code for the layers was extremely complex, it’s hard to improve or add features.  With the code simplifying, I feel I can consider, at least, adding functionality I wouldn’t have been too keen on adding before.

Now, back to work on the code.  We’ll see how this turns out…