These were documented in src/scripts/lib initially because the settings-manager
scripts used to be also there and it made sense to keep them close together.
The intention is to make checks for enabled log topics faster.
Every topic has its own structure that is statically defined in the file
where the logs are printed from. The structure is initialized transparently
when it is first used and it contains all the log level flags for the levels
that this topic should print messages. It is then checked on the wp_log()
macro before printing the message.
Topics from SPA/PipeWire are also handled natively, so messages are printed
directly without checking if the topic is enabled, since the PipeWire and SPA
macros do the checking themselves.
Messages coming from GLib are checked inside the handler.
An internal WpLogFields object is used to manage the state of each log
message, populating all the fields appropriately from the place they
are coming from (wp_log, spa_log, glib log), formatting the message and
then printing it. For printing to the journald, we still use the glib
message handler, converting all the needed fields to GLogField on demand.
That message handler does not do any checks for the topic or the level, so
we can just call it to send the message.
Since the wireplumber configuration has been moved to /usr/share/pipewire, it
does not makes sense to have a different path for the WIREPLUMBER_CONFIG_DIR
environment variable. Therefore, the WIREPLUMBER_CONFIG_DIR environment variable
has been changed to just be an alias of PIPEWIRE_CONFIG_DIR. Finally, Lua
scripts are now installed under /usr/share/wireplumber/scripts instead of
/usr/share/pipewire/scripts as they are a wireplumber feature only.
This adds three meson options to enable or disable building daemon, tools, and modules.
Building the daemon or tools depends on building the modules, and disabling modules without disabling
the other two will result in meson giving an appropriate error.
These new options will let users skip building and installing unneeded items when they are not needed,
e.g. when only using the C API in another application.
After discussing things at the AGL May 2019 F2F meeting
and reflecting on the initial design of WirePlumber,
it became clear that it needed a fresh start.
glib log domains are not like the gstreamer ones, where you can enable
many of them with a wildcard, therefore it is not particularly useful
to have different ones per file
