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.
There is no real use for groups in our API. Just use the name of
the file as the default group and be done with it...
Storing multiple groups with this API is problematic because it
forces flushing the file to disk multiple times, one for each group,
and it's just more performant if we use a prefix in the keys
to implement some form of logical separation.
This commit also makes the GKeyFile a temporary object. As we
always load the file from the file system in _load()
and we always replace its contents with a new dictionary in _save(),
there is no point in keeping the keyfile's internal data structures
stored in memory.
Save errors are now also propagated to adhere to the programming
practices of GObject
