launch: conditionally start rosbag play or cameras

If argument bag is present, start rosbag replay, otherwise use cams.

launch/aruco_tracking.launch

@@ -3,9 +3,10 @@
 <launch>
   <arg name="rviz_config" default="$(find aruco_tracking)/launch/aruco_config.rviz" />
   <arg name="aruco_params" default="$(find aruco_tracking)/config/aruco_params_extended.yaml" />
+  <arg name="bag" default="" />
 
   <!-- RVIZ -->
-  <node name="rviz" pkg="rviz" type="rviz" args="-d $(arg rviz_config)" />
+  <node name="rviz" pkg="rviz" type="rviz" args="-d $(arg rviz_config)" required="true" />
 
   <group ns="aruco_tracking">
     <arg name="manager_name" value="aruco_manager" />
@@ -34,4 +35,12 @@
     <node name="tracking" pkg="aruco_tracking" type="track_boards.py" output="screen" />
   </group>
 
+  <!-- Either start rosbag play (if argument 'bag' is present) -->
+  <node if="$(eval bool(bag))" name="rosbag_play" pkg="rosbag" type="play" args="-l $(arg bag)" />
+  <!-- or start real cameras -->
+  <group if="$(eval not bag)">
+    <include file="$(dirname)/usb_cam_camhs4.launch" />
+    <include file="$(dirname)/usb_cam_camhs6.launch" />
+  </group>
+
 </launch>
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