AP_DDS: Split external control to its own file

* Improves encapsulation, separates concerns

Signed-off-by: Ryan Friedman <ryanfriedman5410+github@gmail.com>

libraries/AP_DDS/AP_DDS_Client.cpp

@@ -12,7 +12,7 @@
 #include <AP_Arming/AP_Arming.h>
 #include <AP_ExternalControl/AP_ExternalControl_config.h>
 #if AP_EXTERNAL_CONTROL_ENABLED
-#include <AP_ExternalControl/AP_ExternalControl.h>
+#include "AP_DDS_ExternalControl.h"
 #endif
 
 #include "AP_DDS_Client.h"
@@ -480,19 +480,7 @@ void AP_DDS_Client::on_topic(uxrSession* uxr_session, uxrObjectId object_id, uin
 
         subscribe_sample_count++;
 #if AP_EXTERNAL_CONTROL_ENABLED
-        auto *external_control = AP::externalcontrol();
-        if (external_control == nullptr) {
-            break;
-        }
-        /*
-          get commands from ENU to NED frame
-         */
-        Vector3f linear_velocity {
-            float(rx_velocity_control_topic.twist.linear.y),
-            float(rx_velocity_control_topic.twist.linear.x),
-            float(-rx_velocity_control_topic.twist.linear.z) };
-        const float yaw_rate = -rx_velocity_control_topic.twist.angular.z;
-        if (!external_control->set_linear_velocity_and_yaw_rate(linear_velocity, yaw_rate)) {
+        if (!AP_DDS_External_Control::handle_velocity_control(rx_velocity_control_topic)) {
             // TODO #23430 handle velocity control failure through rosout, throttled.
         }
 #endif // AP_EXTERNAL_CONTROL_ENABLED

libraries/AP_DDS/AP_DDS_ExternalControl.cpp

@@ -0,0 +1,24 @@
+#if AP_DDS_ENABLED
+
+#include "AP_DDS_ExternalControl.h"
+
+#include <AP_ExternalControl/AP_ExternalControl.h>
+
+bool AP_DDS_External_Control::handle_velocity_control(geometry_msgs_msg_TwistStamped& cmd_vel)
+{
+    auto *external_control = AP::externalcontrol();
+    if (external_control == nullptr) {
+        return false;
+    }
+
+    // Convert commands from ENU to NED frame
+    Vector3f linear_velocity {
+        float(cmd_vel.twist.linear.y),
+        float(cmd_vel.twist.linear.x),
+        float(-cmd_vel.twist.linear.z) };
+    const float yaw_rate = -cmd_vel.twist.angular.z;
+    return external_control->set_linear_velocity_and_yaw_rate(linear_velocity, yaw_rate);
+}
+
+
+#endif // AP_DDS_ENABLED

libraries/AP_DDS/AP_DDS_ExternalControl.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#if AP_DDS_ENABLED
+#include "geometry_msgs/msg/TwistStamped.h"
+
+class AP_DDS_External_Control
+{
+public:
+    static bool handle_velocity_control(geometry_msgs_msg_TwistStamped& cmd_vel);
+};
+#endif // AP_DDS_ENABLED