SKP Generator

The script in this directory generates SKPs of Flutter scenes for use by the Skia team in their regression and performance testing.

Generating the SKPs

Ensure that git and flutter are available on the PATH of your POSIX command line.

Run "build.sh" to generate the SKPs. They will all be placed in the skps/ directory if everything is successful.

WARNING!!! THIS SCRIPT DELETES EVERYTHING NEW IN THIS DIRECTORY. Only files committed to Git before running the script will survive!

Contributing new scenes

Contributions of scenes are welcome. New scenes should be significantly distinct from existing scenes (in terms of visuals and Flutter widgets used to create them), and should either show a scene that is expensive to rasterize, or show an interesting or complex scene from a real-world application.

To contribute a scene, create a stateless widget in its own file in the lib/tests directory, then add a reference to that widget from the lib/main.dart file in the array near the top.

Scenes may have variants, e.g. to show several frames from an animation. This is achieved by passing different arguments to the stateless widget from the array (see lib/main.dart for some examples). In general, the number of variants should be kept small.

Scenes may have complex visual hierarchies but should avoid unnecessary widgets. For example, avoid introducing Navigators, inherited widgets for data models, etc. Leave only the widgets necessary to create the scene statically in one build.

You can use https://debugger.skia.org/ to make sure that you created what you expected (click on EndDrawPicture at the end of the op list to see the final output). The output size is 800x600 at 3dpr.

If you have animations, consider placing all the frames into one image (side by side) to simulate the cost of rendering the entire animation.

Developing

To create the test environment, run build.sh --no-clean. This will skip the final step that deletes build artifacts and thus leave the directory in a state where you can use flutter run, the analyzer, hot reload, and so forth.

You can also edit the void main() in lib/main.dart to call runApp directly with your test widget (then return) so that you bypass the regular logic and can hot reload while you're doing your development.

Troubleshooting

If things don't work, make sure your Flutter version is up to date. This is intended to work against the latest main branch of the flutter/flutter repo.