The gallery demo app is janky on old Android devices with bad GPU drivers, and janky on iOS because of Metal, but those issues are being solved. The main issue

The gallery demo app is janky on old Android devices with bad GPU drivers, and janky on iOS because of Metal, but those issues are being solved. The main issue with iOS and Metal is the shader compilation jank, for which the workaround is shader warm-up that can be automated, but requires an effort from the developer. Dart is single threaded, but the event loop is better than threads for most things, except heavy calculations, but that's what isolates are for. This is probably the best way to do it even in C when latency is important. CPU schedulers tend to leave you with less control over latency when there is underutilization or yielding.