How heavy is reading from a static composition loc...

# compose

[vide]

How heavy is reading from a static composition local? Is it a blazing fast constant time operation, or does it do some tree searching to find the nearest provider? 🤔

[shikasd]

Depends if it is cached (usually it is), but I'd expect something like a map lookup

[romainguy]

No, it’s way more expensive than a map lookup

[romainguy]

On the same device, a Map read is ~60ns, a CompositionLocal read is ~4,000ns

[romainguy]

Derived state is the only thing that’s more expensive

[romainguy]

See benchmark here: https://android-review.googlesource.com/c/platform/frameworks/support/+/2650767

[shikasd]

Static composition local is not a state, so it is cheaper

[shikasd]

Assuming it is inside composition and cached, it should be quite cheap, unless I am missing something

[romainguy]

Ah right sorry I missed the “static” bit

[shikasd]

tbh, Leland's benchmark indicates that static composition local is still expensive, but I didn't look on what exactly it measures

[vide]

The context here is that I need to determine if I'm inside a preview or not many times in every single composable, I'll just cache the value in a global variable instead to avoid uncertainty in performance cost 😅

[Stylianos Gakis]

Are you checking if you're in a preview in your production composable? Why?

[vide]

I was prototyping the viability of a thing. It's a long story! However, I abandoned the idea already 😂