libusb backend: respond to DRAIN command only after reading print_fd

Author: ValdikSS

backend/usb-libusb.c

@@ -440,17 +440,6 @@ print_device(const char *uri,		/* I - Device URI */
       if (FD_ISSET(g.wakeup_pipe[0], &input_set))
 	read(g.wakeup_pipe[0], &dummy, 1);
 
-     /*
-      * If drain output has finished send a response...
-      */
-
-      if (g.drain_output && !nfds && !g.print_bytes)
-      {
-	/* Send a response... */
-	g.drain_output = 0;
-	cupsSideChannelWrite(CUPS_SC_CMD_DRAIN_OUTPUT, CUPS_SC_STATUS_OK, NULL, 0, 1.0);
-      }
-
      /*
       * Check if we have print data ready...
       */
@@ -491,6 +480,17 @@ print_device(const char *uri,		/* I - Device URI */
 		(int)g.print_bytes);
       }
 
+     /*
+      * If drain output has finished send a response...
+      */
+
+      if (g.drain_output && !nfds && !g.print_bytes)
+      {
+	/* Send a response... */
+	g.drain_output = 0;
+	cupsSideChannelWrite(CUPS_SC_CMD_DRAIN_OUTPUT, CUPS_SC_STATUS_OK, NULL, 0, 1.0);
+      }
+
       if (g.print_bytes)
       {
 	iostatus = libusb_bulk_transfer(g.printer->handle,