README.md: add instructions on building and running

README.md

@@ -2,3 +2,100 @@
 
 WirePlumber is a session / policy manager implementation for
 [PipeWire](https://pipewire.org).
+
+# Compiling and Running
+
+## Dependencies
+
+In order to compile WirePlumber you will need:
+
+* GLib >= 2.58
+* PipeWire 0.3 (master)
+
+At the moment, due to heavy development of both PipeWire and WirePlumber,
+it is not always the case that the latest master of WirePlumber works with the
+latest master of PipeWire. The safest PipeWire branch to use with WirePlumber
+master is the `agl-next` branch from
+[my personal clone](https://gitlab.freedesktop.org/gkiagia/pipewire)
+
+## Compilation
+
+WirePlumber uses the meson build system. For compatibility and ease of use,
+though, a Makefile is also provided. The Makefile works only after the initial
+configuration of the project with meson.
+
+Here is the very basic sequence of compiling for the first time:
+```
+$ meson build
+$ make
+```
+
+## Running automated tests
+
+WirePlumber has a few automated tests that you can easily run with:
+
+```
+$ make test
+```
+
+## Running
+
+1. First of all, you will need to run PipeWire. PipeWire itself comes with
+an example session manager that you will need to disable in order to run
+WirePlumber. This can be achieved by editing `src/daemon/pipewire.conf.in`
+on the PipeWire git tree to disable the execution of the session manager:
+
+```
+diff --git a/src/daemon/pipewire.conf.in b/src/daemon/pipewire.conf.in
+index bf64c574..e733e76c 100644
+--- a/src/daemon/pipewire.conf.in
++++ b/src/daemon/pipewire.conf.in
+@@ -24,4 +24,4 @@ load-module libpipewire-module-access
+ load-module libpipewire-module-adapter
+ load-module libpipewire-module-link-factory
+ load-module libpipewire-module-session-manager
+-exec build/src/examples/media-session
++#exec build/src/examples/media-session
+```
+
+2. Second, you will need to run pipewire: in the **pipewire** source tree, do `make run`
+
+3. Without stopping pipewire, in the **wireplumber** source tree, do `make run`
+
+## Testing with an audio client
+
+The easiest way to test that things are working is to start a gstreamer pipeline
+that outputs a test sound to pipewire.
+
+In the **pipewire** source tree, do:
+
+```
+$ make shell
+$ gst-launch-1.0 audiotestsrc ! pwaudiosink
+```
+
+Note that `pwaudiosink` is currently only available in the `agl-next` branch.
+
+## Debugging
+
+The Makefile included with WirePlumber also supports the `gdb` and `valgrind`
+targets. So, instead of `make run` you can do `make gdb` or `make valgrind`
+to do some debugging.
+
+Getting debug messages on the command line is a matter of setting the
+`G_MESSAGES_DEBUG` environment variable as documented in the GLib documentation.
+Usually you can just do:
+
+```
+G_MESSAGES_DEBUG=all make run
+```
+
+Note that this only gives out WirePlumber's debug messages. If you want to also
+see *libpipewire*'s debug messages, then you can also set:
+
+```
+PIPEWIRE_DEBUG=4 G_MESSAGES_DEBUG=all make run
+```
+
+... where `PIPEWIRE_DEBUG` can be set to a value between 1 and 5, with 5 being the
+most verbose and 1 the least verbose.