I don’t understand all the marketing hype about Flutter’s good performance. I can often tell an app is written with Flutter just based on how slow it feels on my iPhone 13 Pro. I think the 120 Hz screen doesn’t help, but there are obvious stutters in even simple apps.
If a current generation flagship phone struggles, then I just can’t imagine how a more affordable phone that is a couple years old would fare.
See Google’s own Google Pay app as an example. Its performance is unforgivably bad. Perhaps it runs better on Android, but on iOS it feels bad.
On iOS there are issues with shader compilation that cause stuttering. A fix is being worked on for quite some time now.
The hype around performance is (I think) because it uses lower level rendering stack and a AOT compiler, but the comparision is being made mainly to JavaScript and web stack tech.
It could be fast as rendering speed depends mainly on how quickly can you rasterize and compose the graphic to the canvas. It uses Skia as the graphics backend, but Skia, while being very feature rich, is not the fastest. Dart is also not the fastest language around, but it has a lot of headroom for optimization. I'm also a bit skeptical about the performance impact of the immutable widgets tree, but maybe it doesn't have such a big performance impact as I imagine.
Overall, Flutter has potential to be quite fast. But currently, due to various issues, it's often not. I do love it though, due to how flexible is the rendering and due to the fact there is no markup language. It's really a joy to work with.
If a current generation flagship phone struggles, then I just can’t imagine how a more affordable phone that is a couple years old would fare.
See Google’s own Google Pay app as an example. Its performance is unforgivably bad. Perhaps it runs better on Android, but on iOS it feels bad.