Yaru tutorial step #3 (handy_window + my_application.cc) no longer produces rounded corners on Ubuntu

[alomia]

Description

In the TL;DR Yaru.dart crash course, steps #2 and #3 indicate that adding handy_window and modifying
linux/runner/my_application.cc should enable modern window behavior (e.g. rounded corners).

Using the current Flutter stable version:

Flutter 3.38.5 (stable)

Dart 3.10.4

Following the tutorial exactly as written produces no visual change:

Window corners remain square

Modifying my_application.cc has no visible effect

Additionally, the file linux/runner/my_application.cc has changed since the tutorial was published, so the instructions in step #3 no longer clearly apply.

This section of the tutorial appears to be outdated and may need to be updated or clarified for recent Flutter versions.

Thanks for maintaining the project.