I'm simply observing the CPU usage of the Flutter app when a TextField gets the focus. I don't see why it matters whatever else may be hogging the CPU as well.

I tried it on macOS as well as on the iOS simulator and on the web, but I haven't tried the latest version yet. You can try the web version here:

https://gallery.flutter.dev/#/demo/cupertino-text-field

Edit: I have now tried the latest version (2.2) and I'm seeing 12% CPU usage for an idle app with nothing but a focused TextField.