Update LiveWindow to provide continuous telemetry. (#771)

LiveWindow.updateValues() is now called from IterativeRobotBase on every
loop iteration.  Telemetry for all WPILib classes is enabled by default;
it can be disabled for specific classes using LiveWindow.disableTelemetry(),
or all telemetry can be disabled using LiveWindow.disableAllTelemetry().

This necessitated changing the hook methodology into other classes to
be more property-based rather than each class providing multiple functions.
This had the benefit of reducing boilerplate and increasing consistency.

- Remove NamedSendable, add name to Sendable.

- Provide SendableBase abstract class.

- Deprecate LiveWindow addSensor/addActuator interfaces.

- Add LiveWindow support to drive classes.

- Add addChild() helper functions to Subsystem.

- Fix inheritance hierarchy.  Now only sensors inherit from SensorBase.
  Other devices inherit from some combination of SendableBase, ErrorBase, or
  nothing.

wpilibc/src/main/native/cpp/Commands/Subsystem.cpp

@@ -9,6 +9,8 @@
 
 #include "Commands/Command.h"
 #include "Commands/Scheduler.h"
+#include "LiveWindow/LiveWindow.h"
+#include "SmartDashboard/SendableBuilder.h"
 #include "WPIErrors.h"
 
 using namespace frc;
@@ -18,10 +20,11 @@ using namespace frc;
  *
  * @param name the name of the subsystem
  */
-Subsystem::Subsystem(const std::string& name) {
-  m_name = name;
+Subsystem::Subsystem(const llvm::Twine& name) {
+  SetName(name, name);
   Scheduler::GetInstance()->RegisterSubsystem(this);
 }
+
 /**
  * Initialize the default command for this subsystem.
  *
@@ -64,14 +67,6 @@ void Subsystem::SetDefaultCommand(Command* command) {
 
     m_defaultCommand = command;
   }
-  if (m_hasDefaultEntry && m_defaultEntry) {
-    if (m_defaultCommand != nullptr) {
-      m_hasDefaultEntry.SetBoolean(true);
-      m_defaultEntry.SetString(m_defaultCommand->GetName());
-    } else {
-      m_hasDefaultEntry.SetBoolean(false);
-    }
-  }
 }
 
 /**
@@ -87,6 +82,20 @@ Command* Subsystem::GetDefaultCommand() {
   return m_defaultCommand;
 }
 
+/**
+ * Returns the default command name, or empty string is there is none.
+ *
+ * @return the default command name
+ */
+llvm::StringRef Subsystem::GetDefaultCommandName() {
+  Command* defaultCommand = GetDefaultCommand();
+  if (defaultCommand) {
+    return defaultCommand->GetName();
+  } else {
+    return llvm::StringRef();
+  }
+}
+
 /**
  * Sets the current command.
  *
@@ -104,6 +113,20 @@ void Subsystem::SetCurrentCommand(Command* command) {
  */
 Command* Subsystem::GetCurrentCommand() const { return m_currentCommand; }
 
+/**
+ * Returns the current command name, or empty string if no current command.
+ *
+ * @return the current command name
+ */
+llvm::StringRef Subsystem::GetCurrentCommandName() const {
+  Command* currentCommand = GetCurrentCommand();
+  if (currentCommand) {
+    return currentCommand->GetName();
+  } else {
+    return llvm::StringRef();
+  }
+}
+
 /**
  * When the run method of the scheduler is called this method will be called.
  */
@@ -118,41 +141,78 @@ void Subsystem::Periodic() {}
  * avoid that situation.
  */
 void Subsystem::ConfirmCommand() {
-  if (m_currentCommandChanged) {
-    if (m_hasCommandEntry && m_commandEntry) {
-      if (m_currentCommand != nullptr) {
-        m_hasCommandEntry.SetBoolean(true);
-        m_commandEntry.SetString(m_currentCommand->GetName());
-      } else {
-        m_hasCommandEntry.SetBoolean(false);
-      }
-    }
-    m_currentCommandChanged = false;
-  }
+  if (m_currentCommandChanged) m_currentCommandChanged = false;
 }
 
-std::string Subsystem::GetName() const { return m_name; }
-
-std::string Subsystem::GetSmartDashboardType() const { return "Subsystem"; }
-
-void Subsystem::InitTable(std::shared_ptr<nt::NetworkTable> subtable) {
-  if (subtable != nullptr) {
-    m_hasDefaultEntry = subtable->GetEntry("hasDefault");
-    m_defaultEntry = subtable->GetEntry("default");
-    m_hasCommandEntry = subtable->GetEntry("hasCommand");
-    m_commandEntry = subtable->GetEntry("command");
-
-    if (m_defaultCommand != nullptr) {
-      m_hasDefaultEntry.SetBoolean(true);
-      m_defaultEntry.SetString(m_defaultCommand->GetName());
-    } else {
-      m_hasDefaultEntry.SetBoolean(false);
-    }
-    if (m_currentCommand != nullptr) {
-      m_hasCommandEntry.SetBoolean(true);
-      m_commandEntry.SetString(m_currentCommand->GetName());
-    } else {
-      m_hasCommandEntry.SetBoolean(false);
-    }
-  }
+/**
+ * Associate a Sendable with this Subsystem.
+ * Also update the child's name.
+ *
+ * @param name name to give child
+ * @param child sendable
+ */
+void Subsystem::AddChild(const llvm::Twine& name,
+                         std::shared_ptr<Sendable> child) {
+  AddChild(name, *child);
+}
+
+/**
+ * Associate a Sendable with this Subsystem.
+ * Also update the child's name.
+ *
+ * @param name name to give child
+ * @param child sendable
+ */
+void Subsystem::AddChild(const llvm::Twine& name, Sendable* child) {
+  AddChild(name, *child);
+}
+
+/**
+ * Associate a Sendable with this Subsystem.
+ * Also update the child's name.
+ *
+ * @param name name to give child
+ * @param child sendable
+ */
+void Subsystem::AddChild(const llvm::Twine& name, Sendable& child) {
+  child.SetName(GetSubsystem(), name);
+  LiveWindow::GetInstance()->Add(&child);
+}
+
+/**
+ * Associate a {@link Sendable} with this Subsystem.
+ *
+ * @param child sendable
+ */
+void Subsystem::AddChild(std::shared_ptr<Sendable> child) { AddChild(*child); }
+
+/**
+ * Associate a {@link Sendable} with this Subsystem.
+ *
+ * @param child sendable
+ */
+void Subsystem::AddChild(Sendable* child) { AddChild(*child); }
+
+/**
+ * Associate a {@link Sendable} with this Subsystem.
+ *
+ * @param child sendable
+ */
+void Subsystem::AddChild(Sendable& child) {
+  child.SetSubsystem(GetSubsystem());
+  LiveWindow::GetInstance()->Add(&child);
+}
+
+void Subsystem::InitSendable(SendableBuilder& builder) {
+  builder.SetSmartDashboardType("Subsystem");
+
+  builder.AddBooleanProperty(
+      "hasDefault", [=]() { return m_defaultCommand != nullptr; }, nullptr);
+  builder.AddStringProperty("default",
+                            [=]() { return GetDefaultCommandName(); }, nullptr);
+
+  builder.AddBooleanProperty(
+      "hasCommand", [=]() { return m_currentCommand != nullptr; }, nullptr);
+  builder.AddStringProperty("command",
+                            [=]() { return GetCurrentCommandName(); }, nullptr);
 }