IOS6 html hardware acceleration changes and how to fix them

http://indiegamr.com/ios6-html-hardware-acceleration-changes-and-how-to-fix-them/

by olsn • 14 years ago

38 26 14 years ago

Having to hint hardware acceleration is bad. The browser shouldn't need to be told. :/

agreed. in the release note it says "Authors should stop using this option as a way to get hardware acceleration"... this sounds like there is an other option to do it, does anyone know?

olsn4• 14 years ago

Not all sites/apps need hardware acceleration and those who do consume a lot more battery. So there is kind of a reason for this - however the way apple implemented this is not from the best quality I think.

The bottom line is, that Apple forces developers to take care of this instead of having everything automatically hardware accalerated and therefore shortening the battery life of iOS devices(by a lot I'm guessing).

TazeTSchnitzel4• 14 years ago

>and therefore shortening the battery life of iOS devices

Does rendering a few more polygons actually kill battery life that badly? I believe much of the OS is already hardware accelerated anyway.

endianswap• 14 years ago

Can someone please explain what tradeoff is being made when Apple decides to hardware accelerate something in their browser? Is it that hardware accelerated elements are more fluid/responsive but require more battery consumption to perform?

I'm used to the PC world where battery/heat are hardly a problem and software rendering is usually a bad thing when hardware rendering is available.

olsn4• 14 years ago

Yes, battery is consumed faster when using the GPU - I cannot tell you by how much, but obviously it is enough on iOS devices for Apple to change its feature sets there.

jarvuschris• 14 years ago

But for doing graphic manipulations, wouldn't it make sense that the net energy used by the GPU getting them done should be less than with the CPU?

chadaustin• 14 years ago

Can you give a citation or backing research? In my experience, if you've got two similar operations, the one on the GPU will consume less power (assuming you don't need to transfer substantially more data over the bus).

panic• 14 years ago

In this case, "hardware accelerated" means drawing web content into an offscreen image -- as the content is transformed using CSS, the image is re-drawn and blended using the GPU. This is faster than re-laying-out and re-drawing the web content directly (even if re-drawing the web content itself uses the GPU). It's a good trade-off when you have animations that update every frame.

The biggest cost is memory. Every pixel of hardware accelerated web content gets 4 bytes of memory. This adds up quickly, especially since any content that overlaps hardware accelerated content must become hardware accelerated as well.

The other big cost, as olsn already pointed out, is that blending these offscreen images onto the screen takes time and power on every frame. In extreme cases this can cause scrolling to stutter.

See the "Optimizing Web Content in UIWebViews and Websites on iOS" session from WWDC 2012 for more information about this.

LinaLauneBaer• 14 years ago

If they disabled the hardware acceleration because the GPU requires more battery I wonder if they have factored in that the rendering needs more time to complete => users will have to stay on the website longer => they have to keep their screen turned on longer which costs also a lot of power...

recursive• 14 years ago

The conspiracy-minded might suspect that the real reason for this might have been to keep web view based apps inconvenient to develop, and poorly performing, to nudge developers towards native ObjC-based apps. Which are coincidentally harder to port to other platforms.

kenferry• 14 years ago

It would, however, indeed be paranoid and crazy.

The WebKit developers spend all day trying to drive the web forward. That's what they do. They're not pulling their punches. Try hanging out in #webkit on irc for a bit and see if you think they want the web to lose to native.

pjmlp3• 14 years ago

Easy solution, just implement the application in native code.

No need for workarounds and hints in an application whose main function is to display _documents_.

lukifer3• 14 years ago

Here's how you make a tasty burger: make a tasty chicken sandwich instead. :P

The issue affects websites as well as hybrid apps. Given that this change is poorly documented by Apple, and it directly affects a JS plugin I'm working on, I'm quite grateful for the OP sharing their findings.

pjmlp3• 14 years ago

hybrid apps are not native.

IOS6 html hardware acceleration changes and how to fix them

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