Documentation: clean up

site/user/quick/desktop.md

+Desktop
+=======
+
+Instructions to get started with Skia on desktop systems (Linux, Mac OS X, or Windows).
+
+1.  [Download Skia](/user/download)
+
+    <!--?prettify lang=sh?-->
+
+        git clone 'https://chromium.googlesource.com/chromium/tools/depot_tools.git'
+        export PATH="${PWD}/depot_tools:${PATH}"
+        git clone 'https://skia.googlesource.com/skia.git'
+        cd skia
+
+    (On Windows without git, swap steps 1 and 2)
+
+2.  Install system-specific prerequisites.
+    -   [Linux](/user/quick/linux)
+    -   [Mac OS X](/user/quick/macos)
+    -   [Windows](/user/quick/windows)
+
+3.  Sync dependencies and config.  Build.  Run tests.
+
+    <!--?prettify lang=sh?-->
+
+        python bin/sync-and-gyp
+        ninja -C out/Debug
+        out/Debug/dm
+
+Gyp Options
+-----------
+
+When running `sync-and-gyp`, the `GYP_DEFINES` environment variable can
+be used to change Skia’s compile-time settings, using a
+space-separated list of key=value pairs. For example, to disable both
+the Skia GPU backend and PDF backends, run it as follows:
+
+<!--?prettify lang=sh?-->
+
+    GYP_DEFINES='skia_gpu=0 skia_pdf=0' python bin/sync-and-gyp
+    ninja -C out/Debug
+
+Note: Setting enviroment variables in the Windows CMD.EXE shell [uses a
+different syntax](./windows#env).
+
+You can also set environment variables such as `CC`, `CXX`,
+`CFLAGS`, or `CPPFLAGS` to control how Skia is compiled. For
+example:
+
+<!--?prettify lang=sh?-->
+
+    CC='clang' CXX='clang++' python bin/sync-and-gyp
+    ninja -C out/Debug
+
+The `GYP_GENERATORS` environment variable can be used to set the
+build systems that you want to use (as a comma-separated list).
+The default is `'ninja,msvs-ninja'` on Windows, `'ninja,xcode'` on
+Mac OS X, and just `'ninja'` on Linux.  For example, to generate
+only Ninja files on Mac:
+
+<!--?prettify lang=sh?-->
+
+    GYP_GENERATORS='ninja' python bin/sync-and-gyp
+    ninja -C out/Debug
+
+Finally, the `SKIA_OUT` environment variable can be used to set
+the path for the build directory.  The default is `out` inside the
+top-level Skia source directory.  For example to test Skia with
+two different compilers:
+
+<!--?prettify lang=sh?-->
+
+    CC='clang' CXX='clang++' SKIA_OUT=~/build/skia_clang python bin/sync-and-gyp
+    CC='gcc'   CXX='g++'     SKIA_OUT=~/build/skia_gcc   python bin/sync-and-gyp
+    ninja -C ~/build/skia_clang/Debug
+    ninja -C ~/build/skia_gcc/Debug
+
+Run unit and correctness tests
+------------------------------
+
+[DM](../../dev/testing/testing) ("diamond master") is the Skia test app.
+
+<!--?prettify lang=sh?-->
+
+    ninja -C out/Debug dm
+    out/Debug/dm
+
+Run Skia samples
+----------------
+
+[SampleApp](../sample/sampleapp) is the Skia sample program.
+
+<!--?prettify lang=sh?-->
+
+    ninja -C out/Debug SampleApp
+    out/Debug/SampleApp
+
+Build non-debug binaries
+------------------------
+
+The usual mode you want for testing is Debug mode (`SK_DEBUG` is
+defined, and debug symbols are included in the binary). If you
+would like to build the Release mode:
+
+<!--?prettify lang=sh?-->
+
+    ninja -C out/Release
+
+Performance tests
+-----------------
+
+Build and run nanobench (performance tests). In this case, we will
+build with the "Release" configuration, since we are running
+performance tests.
+
+<!--?prettify lang=sh?-->
+
+    ninja -C out/Release nanobench
+    out/Release/nanobench
+    out/Release/nanobench --skps .../path/to/*.skp
+
+<!-- TODO(mtklein): document nanobench -->
+
+Keeping up to date
+------------------
+
+<!--?prettify lang=sh?-->
+
+    git fetch origin
+    git checkout origin/master
+
+Contribute to Skia
+------------------
+
+[How to use Git and Git-cl to contribute to Skia](/dev/contrib/submit).