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by incrudible 1289 days ago
GPUs have no concept of animation. A frame rendered by a GPU has a fixed state, usually computed on the CPU. Until recently, this was usually done on the main thread, because graphics APIs had poor support for being used from multiple threads. I have no idea what AirBNB was doing to fail 60Hz on rather simple scenes with a single thread, but you can rest assured that it is possible without multiple threads or even processes.
1 comments
halpmeh 1289 days ago
The point is that iOS has always used a separate process for computing the GPU state. Android does this on the main thread, which is why Android feels like garbage. And I say this as a former Android developer. Animations on Android feel like peanut butter. They always will until they are moved off the main thread.
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incrudible 1288 days ago
No, it has not. If you talked to the GPU through OpenGL, you did it on the main thread. You pass all the state that you computed in that thread. Chances are you computed that state in that thread too.

There are some optimizations regarding e.g. scrolling being computed in a different thread/process (still on the CPU) before compositing (on the GPU) but that is not a requirement for smooth animation.

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vvanders 1289 days ago
That's not technically correct(which is always the best kind of correct :) ), HWUI has been multithreaded for quite a long while now. That doesn't prevent apps from doing bad things but it's been possible to do smooth animation on Android since the days of project butter.
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ricardobeat 1288 days ago
My low-end Android device disagrees. Eight cores @ 2.3ghz and _everything_ stutters, on a barebones OS with nothing installed.

Pixel phones fare a lot better, but I suspect it's just a result of their sheer processing power.

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incrudible 1288 days ago
> barebones OS

Android is the opposite of barebones. It comes loaded with crap, much of it is using "stop the world" garbage collection while also producing lots of garbage. Building on Java is Android's original sin. You could still build an NDK app, talk to OpenGL, and hit 60Hz on low-end devices, years ago, but that's not how most stuff is developed. There are layers upon layers of crap between applications and the hardware, to the point where apparently people have come to believe that you need special OS interfaces to do smooth animation.

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halpmeh 1289 days ago
How do you animate on the HWUI thread?
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