Migrate a Windows project to ensure the window is shown

Flutter 3.13 fixed a bug that could result in the window not being shown. Windows projects created using Flutter 3.7 or Flutter 3.10 need to be migrated to fix this issue.

Migration steps

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Verify you are on Flutter version 3.13 or newer using flutter --version. If needed, use flutter upgrade to update to the latest version of the Flutter SDK.

Projects that have not modified their windows/runner/flutter_window.cpp file will be migrated automatically by flutter run or flutter build windows.

Projects that have modified their windows/runner/flutter_window.cpp file might need to migrate manually.

Code before migration:

cpp
flutter_controller_->engine()->SetNextFrameCallback([&]() {
  this->Show();
});

Code after migration:

cpp
flutter_controller_->engine()->SetNextFrameCallback([&]() {
  this->Show();
});

// Flutter can complete the first frame before the "show window" callback is
// registered. The following call ensures a frame is pending to ensure the
// window is shown. It is a no-op if the first frame hasn't completed yet.
flutter_controller_->ForceRedraw();

Example

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