Okay, I figured it out with the help of the iOS Emulator, and Xcode Instruments to profile it. (I'm not sure if I should add my solution into the main question, or as an answer, but I thought I'd do it this way as my question is already a little cluttered).
As it turns out, it was actually some erroneous javascript causing the issue, but apparently only on iOS.
The web-app is intended to only be a single page high (no vertical scrolling, except within specific DIV
s), so in addition to the usual standard JS code for hiding the address bar...
window.addEventListener("load",function() {
// Set a timeout...
setTimeout(function(){
// Hide the address bar!
window.scrollTo(0, 1);
}, 0);
});
...I had also added in the following:
$(document).scroll(
function(e){
window.scrollTo(0, 1);
});
From looking at the profile results, I was able to see that a lot of time was being spent in scrollTo
, so it immediately pointed to this as the cause. Why the scroll
event was being triggered so much, I have no idea (this was occurring with no touching of the screen whatsoever).
My initial fix is to throttle that code, but I am now evaluating whether or not I even need it at all. Here is the code I have that fixes it for now (using jquery-debounce, which I was already using for something else):
$(document).scroll(
$.throttle(function(e){
window.scrollTo(0, 1);
})
, 10);
The download time of the application cache is now in line with the Android times. Phew!