why does flutter app have bad performance when launching them - flutter

Question

I'm trying to make my app performant.
I'm using dart devtools and when i check the graph I see that there is some shader compilation detected when launching the app for the first time, I thought that my app has a problem but i tried to run the code that flutter provides us when creating a new project and boom the result was the same.
I want to know if there is someone that encountred the same problem ?
Ps : i tested the app on a real device with os Android 12 and CPU ARM X64.
there is my code :
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return const MaterialApp(
title: 'Sample App',
home: MyHomePage(
title: 'App',
),
);
}
}
class MyHomePage extends StatelessWidget {
const MyHomePage({super.key, required this.title});
final String title;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(title),
),
body: Center(
child: Column(
children: const [
Text('hello'),
],
),
),
);
}
}

Answer 1

As I understand your problem, you want to reduce the time your app needs to start and found the shader compilation to be a big part of it. If that understanding is correct, this might help:
First, you can not "disable" shader compilation, every flutter application needs to compile the shaders for rendering, but it heavily depends on your application, how much time that takes (many animations for example are bad here)
Second, since Flutter 1.20, you can use the SkSL warmup to reduce the startup time for compiling your shaders. The idea being, that you compile the shader once and save it for faster startup times.
You can test this feature while in development with
flutter run --cache-sksl
this will take more time than before, but afterwards, your flutter run commands will be faster.
If you want to build your application with SkSL warmup, you have to write the SkSL shaders into a file by pressing "M" while in the command line of flutter run, then you can use:
flutter build ios --bundle-sksl-path flutter_01.sksl.json
to build the application. More information can be found here.
I tested this with the small program you sent, for normal startup it needed 25.9ms for the shader compilation, caching the sksl file needed 225.9ms, and flutter run afterwards needed 9.6ms for the shaders. Therefore caching sksl made it about 63% faster (it was only one short test, so the results are no medians or anything, so the meaningfulness of this test is debatable).
Lastly, you should always test your performance in release builds, not in debug mode. Debugging your application has a large overhead and much worse performance than released applications. Have a look at Flutter build modes for more information.