DRMBackend: Add libliftoff log handler

This serves to attribute the origin of any spurious logging libliftoff
would be doing. Otherwise, it simply writes to stderr, and sometimes
without any hint that it is coming from libliftoff.

Signed-off-by: Samuel Dionne-Riel <[email protected]>

src/Backends/DRMBackend.cpp

@@ -536,6 +536,7 @@ extern GamescopePanelOrientation g_DesiredInternalOrientation;
 extern bool g_bForceDisableColorMgmt;
 
 static LogScope drm_log( "drm" );
+static LogScope liftoff_log_scope( "liftoff" );
 
 static std::unordered_map< std::string, std::string > pnps = {};
 
@@ -1094,6 +1095,27 @@ extern bool env_to_bool(const char *env);
 uint32_t g_uAlwaysSignalledSyncobj = 0;
 int g_nAlwaysSignalledSyncFile = -1;
 
+static void
+gamescope_liftoff_log_handler(enum liftoff_log_priority liftoff_priority, const char *fmt, va_list args)
+{
+	enum LogPriority priority = LOG_DEBUG;
+
+	switch ( liftoff_priority )
+	{
+		case LIFTOFF_ERROR:
+			priority = LOG_ERROR;
+			break;
+		case LIFTOFF_DEBUG:
+			priority = LOG_DEBUG;
+			break;
+		case LIFTOFF_SILENT:
+			priority = LOG_SILENT;
+			break;
+	}
+
+	liftoff_log_scope.vlogf(priority, fmt, args);
+}
+
 bool init_drm(struct drm_t *drm, int width, int height, int refresh)
 {
 	load_pnps();
@@ -1267,8 +1289,9 @@ bool init_drm(struct drm_t *drm, int width, int height, int refresh)
 	std::thread flip_handler_thread( flip_handler_thread_run );
 	flip_handler_thread.detach();
 
-	if ( drm->bUseLiftoff )
-		liftoff_log_set_priority(g_bDebugLayers ? LIFTOFF_DEBUG : LIFTOFF_ERROR);
+	// Set log priority to the max, liftoff_log_scope will filter for us.
+	liftoff_log_set_priority(LIFTOFF_DEBUG);
+	liftoff_log_set_handler(gamescope_liftoff_log_handler);
 
 	hdr_output_metadata sdr_metadata;
 	memset(&sdr_metadata, 0, sizeof(sdr_metadata));