Add callback handlers for LiveWindow (#2053)

Fixes #2223

wpilibOldCommands/src/main/java/edu/wpi/first/wpilibj/command/Scheduler.java

@@ -17,6 +17,7 @@ import edu.wpi.first.hal.HAL;
 import edu.wpi.first.networktables.NetworkTableEntry;
 import edu.wpi.first.wpilibj.Sendable;
 import edu.wpi.first.wpilibj.buttons.Trigger.ButtonScheduler;
+import edu.wpi.first.wpilibj.livewindow.LiveWindow;
 import edu.wpi.first.wpilibj.smartdashboard.SendableBuilder;
 import edu.wpi.first.wpilibj.smartdashboard.SendableRegistry;
 
@@ -95,11 +96,20 @@ public final class Scheduler implements Sendable, AutoCloseable {
   private Scheduler() {
     HAL.report(tResourceType.kResourceType_Command, tInstances.kCommand_Scheduler);
     SendableRegistry.addLW(this, "Scheduler");
+    LiveWindow.setEnabledListener(() -> {
+      disable();
+      removeAll();
+    });
+    LiveWindow.setDisabledListener(() -> {
+      enable();
+    });
   }
 
   @Override
   public void close() {
     SendableRegistry.remove(this);
+    LiveWindow.setEnabledListener(null);
+    LiveWindow.setDisabledListener(null);
   }
 
   /**

wpilibOldCommands/src/main/native/cpp/commands/Scheduler.cpp

@@ -20,6 +20,7 @@
 #include "frc/buttons/ButtonScheduler.h"
 #include "frc/commands/Command.h"
 #include "frc/commands/Subsystem.h"
+#include "frc/livewindow/LiveWindow.h"
 #include "frc/smartdashboard/SendableBuilder.h"
 #include "frc/smartdashboard/SendableRegistry.h"
 
@@ -198,9 +199,20 @@ Scheduler::Scheduler() : m_impl(new Impl) {
   HAL_Report(HALUsageReporting::kResourceType_Command,
              HALUsageReporting::kCommand_Scheduler);
   SendableRegistry::GetInstance().AddLW(this, "Scheduler");
+  auto scheduler = frc::LiveWindow::GetInstance();
+  scheduler->enabled = [this] {
+    this->SetEnabled(false);
+    this->RemoveAll();
+  };
+  scheduler->disabled = [this] { this->SetEnabled(true); };
 }
 
-Scheduler::~Scheduler() {}
+Scheduler::~Scheduler() {
+  SendableRegistry::GetInstance().Remove(this);
+  auto scheduler = frc::LiveWindow::GetInstance();
+  scheduler->enabled = nullptr;
+  scheduler->disabled = nullptr;
+}
 
 void Scheduler::Impl::Remove(Command* command) {
   if (!commands.erase(command)) return;