Hacking on Sky

Building

  • Follow the setup & build instructions for Mojo

The build directory will be out/Debug for Linux debug builds, and out/Release for Linux release builds. For Android builds, prefix android_, as in, android_Debug.

For Sky on iOS, you can try following these experimental instructions.

Running applications

To run an application on your device, run:

  • ./mojo/tools/mojodb start out/android_Debug [url]

mojodb has numerous commands, visible via mojodb help. Common ones include:

  • mojodb start BUILD_DIR [url]
  • mojodb load [url]
  • mojodb stop
  • mojodb start_tracing # Starts recoding a performance trace (use stop_tracing to stop)
  • mojodb print_crash # Symbolicate the most recent crash from android.

Once mojodb start is issued, all subsequent commands will be sent to the running mojo_shell instance (even on an attached android device). mojodb start reads gn args from the passed build directory to determine whether its using android, for example.

Running tests

Tests are only supported on Linux currently.

  • ./sky/tools/test_sky --debug
    • This runs the tests against //out/Debug. If you want to run against //out/Release, omit the --debug flag.

Running tests manually

Running tests manually lets you more quickly iterate during development; rather than having to compile and rerun all the tests, then trawl through the build output to find the current results, you can just run the test you're working on and reload it over and over, seeing the output right there on your console.

  • sky/tools/skygo/linux64/sky_server -v -p 8000 out/Debug out/Debug/gen/dart-pkg/packages
  • out/Debug/mojo_shell --args-for="mojo:native_viewport_service --use-headless-config --use-osmesa" --args-for"=mojo:sky_viewer --testing" --content-handlers=application/dart,mojo:sky_viewer --url-mappings=mojo:window_manager=mojo:sky_tester,mojo:surfaces_service=mojo:fake_surfaces_service mojo:window_manager
  • The sky_tester should print #READY when ready
  • Type the URL you wish to run, for example http://127.0.0.1:8000/sky/tests/widgets/dialog.dart, and press the enter key
  • The harness should print the results of the test. You can then type another URL.

Writing tests

We recommend using the Dart test testing framework. See sky/tests/raw/color_bounds.dart for an example.

Debugging Sky

This document aims to explain how to debug Sky itself.

C++

Launch a debug Sky build on Linux as follows (where app.dart is the test you are running and trying to debug):

mojodb start --gdb out/Debug app.dart
mojodb gdb_attach

Once gdb has loaded, hit c to start the app. The linux simulator will load (slowly), after spawning many threads. When your app crashes, it will pause in the debugger. At that point, regular gdb commands will work: n to step over the current statement, s to step into the current statement, f to step out of the current block, c to continue until the next breakpoint or exception.

Dart

Use Observatory.