# Prerequisites To compile CanvasKit, you will first need to [install `emscripten`][1]. This will set the environment `EMSDK` (among others) which is required for compilation. Which version should you use? [`/infra/wasm-common/docker/emsdk-base/Dockerfile`][2] shows the version we build and test with. We try to keep this up-to-date. [1]: https://emscripten.org/docs/getting_started/downloads.html [2]: https://github.com/google/skia/blob/master/infra/wasm-common/docker/emsdk-base/Dockerfile This document also assumes you have followed the instructions to download Skia and its deps . ## MacOS specific notes Make sure you have Python3 installed, otherwise the downloading emscripten toolchain can fail with errors about SSL certificates. See also for a solution to Python3 using the wrong certificates. # Compile and Run Local Example ``` make release # make debug is much faster and has better error messages make local-example ``` This will print a local endpoint for viewing the example. You can experiment with the CanvasKit API by modifying `./npm_build/example.html` and refreshing the page. For some more experimental APIs, there's also `./npm_build/extra.html`. For other available build targets, see `Makefile` and `compile.sh`. For example, building a stripped-down version of CanvasKit with no text support or any of the "extras", one might run: ./compile.sh no_skottie no_particles no_font Such a stripped-down version is about half the size of the default release build. # Unit tests, performance tests, and coverage. To run unit tests and compute test coverage on a debug gpu build ``` make debug make test-continuous ``` This reads karma.conf.js, and opens a chrome browser and begins running all the test in `test/` it will detect changes to the tests in that directory and automatically run again, however it will automatically rebuild and reload canvaskit. Closing the chrome window will just cause it to re-opened. Kill the karma process to stop continuous monitoring for changes. The tests are run with whichever build of canvaskit you last made. be sure to also test with `release`, `debug_cpu`, and `release_cpu`. testing with release builds will expose problems in closure compilation and usually forgotten externs. ## Coverage Coverage will be automatically computed when running test-continuous locally. Note that the results will only be useful when testing a debug build. Open `coverage//index.html` For a summary and detailed line-by-line result. ## Measuring Performance We use puppeteer to run a Chrome browser to gather performance data in a consistent way. See //tools/perf-canvaskit-puppeteer for more. ## Adding tests The tests in `tests/` are grouped into files by topic. Within each file there are `describe` blocks further organizing the tests, and within those `it()` functions which test particular behaviors. `describe` and `it` are jasmine methods which can both be temporarily renamed `fdescribe` and `fit`. Which causes jasmine to only those. We have also defined `gm` which is a method for defining a test which draws something to a canvas that is shapshotted and reported to gold.skia.org, where you can compare it with the snapshot at head. ## Testing from Gerrit When submitting a CL in gerrit, click "choose tryjobs" and type canvaskit to filter them. select all of them, which at the time of this writing is four jobs, for each combination of perf/test gpu/cpu. The performance results are reported to perf.skia.org gold results are reported to gold.skia.org Coverage is not measured while running tests this way. # Inspecting output WASM The `wasm2wat` tool from [the WebAssembly Binary Toolkit](https://github.com/WebAssembly/wabt) can be used to produce a human-readable text version of a `.wasm` file. The output of `wasm2wat --version` should be `1.0.13 (1.0.17)`. This version has been checked to work with the tools in `wasm_tools/SIMD/`. These tools programmatically inspect the `.wasm` output of a CanvasKit build to detect the presence of [wasm SIMD](https://github.com/WebAssembly/simd) operations. # Infrastructure Playbook When dealing with CanvasKit (or PathKit) on our bots, we use Docker. Check out $SKIA_ROOT/infra/wasm-common/docker/README.md for more on building/editing the images used for building and testing. ## Updating the version of Emscripten we build/test with This presumes you have updated emscripten locally to a newer version of the sdk and verified/fixed any build issues that have arisen. 1. Edit `$SKIA_ROOT/infra/wasm-common/docker/emsdk-base/Dockerfile` to install and activate the desired version of Emscripten. 2. Edit `$SKIA_ROOT/infra/wasm-common/docker/Makefile` to have `EMSDK_VERSION` be set to that desired version. If there is a suffix that is not `_v1`, reset it to be `_v1`. If testing the image later does not work and edits are made to the emsdk-base Dockerfile to correct that, increment to `_v2`,`_v3`, etc to force the bots to pick up the new image. 3. In `$SKIA_ROOT/infra/wasm-common/docker/`, run `make publish_emsdk_base` 4. Edit `$SKIA_ROOT/infra/canvaskit/docker/canvaskit-emsdk/Dockerfile` to be based off the new version from step 2. CanvasKit has its own docker image because it needs a few extra dependencies to build with font support. 5. Edit `$SKIA_ROOT/infra/canvaskit/docker/Makefile` to have the same version from step 2. It's easiest to keep the `emsdk-base` and `canvaskit-emsdk` versions be in lock-step. 6. In `$SKIA_ROOT/infra/canvaskit/docker/`, run `make publish_canvaskit_emsdk`. 7. In `$SKIA_ROOT/infra/bots/recipe_modules/build/`, update `canvaskit.py` and `pathkit.py` to have `DOCKER_IMAGE` point to the desired tagged Docker containers from steps 2 and 5 (which should be the same). 8. In `$SKIA_ROOT/infra/bots/task_drivers/compile_wasm_gm_tests.go`, update dockerImage to refer to the desired Docker containers from steps 2 and 5. 9. In `$SKIA_ROOT/infra/bots/`, run `make train` to re-train the recipes. 10. Optional: Run something like `git grep 1\\.38\\.` in `$SKIA_ROOT` to see if there are any other references that need updating. 11. Upload a CL with all the changes. Run all Test.+CanvasKit, Perf.+Puppeteer, Test.+PathKit, Perf.+PathKit jobs to make sure the new builds pass all tests and don't crash the perf harnesses. 12. Send out CL for review. Feel free to point the reviewer at these steps.