The primary motivation for the WindowManager Shell (WMShell) library is to effectively scale WindowManager by making it easy™ and safe to create windowing features to fit the needs of various Android products and form factors.
To achieve this, WindowManager separates the policy of managing windows (WMCore) from the presentation of surfaces (WMShell) and provides a minimal interface boundary for the two to communicate.
Currently, the WMShell library is used to drive the windowing experience on handheld (phones & tablets), TV, Auto, Arc++, and Wear to varying degrees.
The core WMShell library code is currently located in the frameworks/base/libs/WindowManager/Shell directory and is included as a part dependency of the host SystemUI apk.
The library can be built directly by running (using go/makepush):
mp :WindowManager-Shell
But this is mainly useful for inspecting the contents of the library or verifying it builds. The various targets can be found in the Shell library's Android.bp file.
Normally, you would build it as a part of the host SystemUI, for example via commandline:
# Phone SystemUI variant mp sysuig # Building Shell & SysUI changes along w/ framework changes mp core services sysuig
Or preferably, if you are making WMShell/SysUI only changes (no other framework changes), then building via go/sysui-studio allows for very quick iteration (one click build and push of SysUI in < 30s).
If you are making framework changes and are using aidegen to set up your platform IDE, make sure to include the appropriate directories to build, for example:
# frameworks/base will include base/libs/WindowManager/Shell and base/packages/SystemUI aidegen frameworks/base \ vendor/<oem>/packages/SystemUI \ ...