Improve iOS application responsiveness

If you’ve been working on an application (either web based or wrapped on in a cocoa layer) and you’ve noticed that it just seems slower than a native app then your not alone. I was experiencing this a while ago and wanted a decent way to fix it. After reading up the iOS developer guidelines and playing around a bit I found the reason, and a fix.

The cause of the problem is simple, the system is waiting. When you tap the screen it fires off a series of events, but not back to back. The <code>onclick</code> event, the one that most the web uses, it delayed a bit. This is done so the system has a chance to check for various gestures, primarily double click which zooms. The firing order goes something like this:

  1. touch start, as soon as your finger touches the screen.
  2. touch end, as soon as your finger leaves the screen
  3. mouse down, no less than 350 milliseconds after touchstart
  4. mouse up, about 5 milliseconds after mouse down
  5. click, 1 millisecond after mouseup
I’ve uploaded a page that shows the delays, you can check out the Fire Order Example here. There are two solutions to this, first is the overkill method, simple fake a click every time you touch the screen, something like this:

That should work just fine, but personally I think it’s a bit overkill, instead I usually declare each click area with an initial control init. If your building an app with a lot of different inputs and want to clare them on the button using the inline <code>onclick=””</code> trigger than that might just me your ticked if you want a bit of speed improvement. Now I havent’ tested that code but it should work, if not I can test a trigger function that will work, just leave a a note in the comments.

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