1Skia Viewer 2========================== 3The Skia Viewer displays a series of slides that exhibit specific features of Skia, including the Skia golden master images (or GMs) and programmed samples that allow interaction. In addition, the Viewer is used to debug and understand different parts of the Skia system: 4 5* Observe rendering performance - placing the Viewer in stats mode displays average frame times. 6* Try different rendering methods - it's possible to cycle among the three rendering methods: raster, OpenGL and Vulkan (on supported platforms). You can use this with stats mode to see the effect that the different rendering methods have on drawing performance. 7* Display and manipulate your own pictures. 8 9Some slides require resources stored outside the program. These resources are stored in the `<skia-path>/resources` directory. 10 11Linux, Macintosh and Windows 12---------------------------- 13 14The Viewer can be built using the regular GN build process, e.g. 15 16 bin/gn gen out/Release --args='is_debug=false' 17 ninja -C out/Release/viewer 18 19To load resources in the desktop Viewers, use the `--resourcePath` option: 20 21 <skia-path>/out/Release/viewer --resourcePath <skia-path>/resources 22 23Similarly, `--skps <skp-file-path>` will load any `.skp` files in that directory for display within the Viewer. 24 25Other useful command-line options: using `--match <pattern>` will load only SKPs or slides matching that name; using `--slide <name>` will launch at that slide; and you can start up with a particular rendering method by using `--backend`, i.e., `--backend sw`, `--backend gl`, or `--backend vk`. 26 27The desktop Viewers are controlled using the keyboard and mouse: left (←) and right (→) arrows to move from slide to slide; up (↑) and down (↓) arrows to zoom in and out; clicking and dragging will translate. Other display options and a slide picker can be found in the Tools UI, which can be toggled by hitting the spacebar. 28 29Key | Action 30-----------------------------|------------- 31← → | Move between the slides 32↑ ↓ | Zoom in / out 33d | Change render methods among raster, OpenGL and Vulkan 34s | Display rendering times and graph 35Space | Toggle display of Tools UI 36 37Android 38------- 39 40To build Viewer as an Android App, you will need the 41[Android SDK](https://developer.android.com/studio/#command-tools) installed and your `ANDROID_HOME` environment variable set. 42 43 mkdir ~/android-sdk 44 ( cd ~/android-sdk; unzip ~/Downloads/sdk-tools-*.zip ) 45 yes | ~/android-sdk/tools/bin/sdkmanager --licenses 46 export ANDROID_HOME=~/android-sdk # Or wherever you installed the Android SDK. 47 48The Viewer APK must be built by gradle which can be invoked on the command line 49with the following script: 50 51 platform_tools/android/bin/android_build_app -C <out_dir> viewer 52 53where `<out_dir>` is the ninja out directory for android (e.g., `out/arm64`) 54that you want to use to build the app. Upon completion of the script the APK 55can be found at `<out_dir>/viewer.apk` 56 57To load resources in the Android Viewer place them in 58`/data/local/tmp/resources`; to load SKPs place them in `/data/local/tmp/skps`. 59 60Swiping left and right will switch slides, pinch-zoom will zoom in and out, and 61display options are available in the UI. 62 63iOS 64--- 65 66The viewer is not yet fully supported on iOS, but can be used to display 67individual slides on a device by launching via `ios-deploy` with the `--match` 68or `--slide` command-line options. The viewer will automatically bundle the 69`resources` directory in the top-level Skia directory, and will bundle an 70`skps` directory if also placed in the Skia directory. 71