[PATCH BlueZ] mpris-proxy: Line-buffer stdout

[Seonggon Cho <jmsmg1@me.com>]

mpris-proxy reports adapter and player changes with printf() but never
flushes stdout. When it runs as a service (tools/mpris-proxy.service)
stdout is a pipe to the journal, so glibc fully buffers it and nothing
is written until 4 KiB have accumulated or the process exits.

On a system whose Bluetooth adapter went away and came back every two
minutes, the "Bluetooth Adapter /org/bluez/hci0 removed" and "... found"
messages reached the journal in bursts of exactly 100 lines (about
4096 bytes), all carrying the timestamp of the flush rather than of the
event, i.e. up to about 80 minutes late.

Set stdout to line buffered at startup, as bt_shell_init() already does,
so every message reaches the journal with an accurate timestamp.

Assisted-by: Claude:claude-fable-5-1
---
 tools/mpris-proxy.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/mpris-proxy.c b/tools/mpris-proxy.c
index 1d7a421e9..4a8dd71e2 100644
--- a/tools/mpris-proxy.c
+++ b/tools/mpris-proxy.c
@@ -2954,6 +2954,10 @@ int main(int argc, char *argv[])
 	guint owner_watch, properties_watch, signal_watch;
 	struct sigaction sa;
 
+	/* stdout is a pipe to the journal when running as a service, so make
+	 * it line buffered to get the messages out as they happen. */
+	setlinebuf(stdout);
+
 	context = g_option_context_new(NULL);
 	g_option_context_add_main_entries(context, options, NULL);
 
-- 
2.55.0