[wpilibc] Shuffleboard SimpleWidget: Return pointer instead of reference (#4703)

Based on beta test feedback, returning a pointer is more intuitive, as
typically the return value is late bound to an instance variable.

wpilibc/src/main/native/cpp/shuffleboard/ShuffleboardContainer.cpp

@@ -83,7 +83,7 @@ SimpleWidget& ShuffleboardContainer::Add(std::string_view title,
   auto ptr = widget.get();
   m_components.emplace_back(std::move(widget));
   ptr->GetEntry(nt::GetStringFromType(defaultValue.type()))
-      .SetDefault(defaultValue);
+      ->SetDefault(defaultValue);
   return *ptr;
 }
 
@@ -322,7 +322,7 @@ SimpleWidget& ShuffleboardContainer::AddPersistent(
     std::string_view title, const nt::Value& defaultValue) {
   auto& widget = Add(title, defaultValue);
   widget.GetEntry(nt::GetStringFromType(defaultValue.type()))
-      .GetTopic()
+      ->GetTopic()
       .SetPersistent(true);
   return widget;
 }

wpilibc/src/main/native/cpp/shuffleboard/SimpleWidget.cpp

@@ -14,19 +14,19 @@ SimpleWidget::SimpleWidget(ShuffleboardContainer& parent,
                            std::string_view title)
     : ShuffleboardValue(title), ShuffleboardWidget(parent, title), m_entry() {}
 
-nt::GenericEntry& SimpleWidget::GetEntry() {
+nt::GenericEntry* SimpleWidget::GetEntry() {
   if (!m_entry) {
     ForceGenerate();
   }
-  return m_entry;
+  return &m_entry;
 }
 
-nt::GenericEntry& SimpleWidget::GetEntry(std::string_view typeString) {
+nt::GenericEntry* SimpleWidget::GetEntry(std::string_view typeString) {
   if (!m_entry) {
     m_typeString = typeString;
     ForceGenerate();
   }
-  return m_entry;
+  return &m_entry;
 }
 
 void SimpleWidget::BuildInto(std::shared_ptr<nt::NetworkTable> parentTable,

wpilibc/src/main/native/include/frc/shuffleboard/SimpleWidget.h

@@ -27,17 +27,19 @@ class SimpleWidget final : public ShuffleboardWidget<SimpleWidget> {
 
   /**
    * Gets the NetworkTable entry that contains the data for this widget.
-   * The widget owns the entry.
+   * The widget owns the entry; the returned pointer's lifetime is the same as
+   * that of the widget.
    */
-  nt::GenericEntry& GetEntry();
+  nt::GenericEntry* GetEntry();
 
   /**
    * Gets the NetworkTable entry that contains the data for this widget.
-   * The widget owns the entry.
+   * The widget owns the entry; the returned pointer's lifetime is the same as
+   * that of the widget.
    *
    * @param typeString NT type string
    */
-  nt::GenericEntry& GetEntry(std::string_view typeString);
+  nt::GenericEntry* GetEntry(std::string_view typeString);
 
   void BuildInto(std::shared_ptr<nt::NetworkTable> parentTable,
                  std::shared_ptr<nt::NetworkTable> metaTable) override;

wpilibc/src/test/native/cpp/shuffleboard/ShuffleboardInstanceTest.cpp

@@ -25,14 +25,14 @@ TEST(ShuffleboardInstanceTest, PathFluent) {
   NTWrapper ntInst;
   frc::detail::ShuffleboardInstance shuffleboardInst{ntInst.inst};
 
-  auto& entry = shuffleboardInst.GetTab("Tab Title")
-                    .GetLayout("List", "List Layout")
-                    .Add("Data", "string")
-                    .WithWidget("Text View")
-                    .GetEntry();
+  auto entry = shuffleboardInst.GetTab("Tab Title")
+                   .GetLayout("List", "List Layout")
+                   .Add("Data", "string")
+                   .WithWidget("Text View")
+                   .GetEntry();
 
-  EXPECT_EQ("string", entry.GetString("")) << "Wrong entry value";
-  EXPECT_EQ("/Shuffleboard/Tab Title/List/Data", entry.GetTopic().GetName())
+  EXPECT_EQ("string", entry->GetString("")) << "Wrong entry value";
+  EXPECT_EQ("/Shuffleboard/Tab Title/List/Data", entry->GetTopic().GetName())
       << "Entry path generated incorrectly";
 }
 
@@ -40,17 +40,17 @@ TEST(ShuffleboardInstanceTest, NestedLayoutsFluent) {
   NTWrapper ntInst;
   frc::detail::ShuffleboardInstance shuffleboardInst{ntInst.inst};
 
-  auto& entry = shuffleboardInst.GetTab("Tab")
-                    .GetLayout("First", "List")
-                    .GetLayout("Second", "List")
-                    .GetLayout("Third", "List")
-                    .GetLayout("Fourth", "List")
-                    .Add("Value", "string")
-                    .GetEntry();
+  auto entry = shuffleboardInst.GetTab("Tab")
+                   .GetLayout("First", "List")
+                   .GetLayout("Second", "List")
+                   .GetLayout("Third", "List")
+                   .GetLayout("Fourth", "List")
+                   .Add("Value", "string")
+                   .GetEntry();
 
-  EXPECT_EQ("string", entry.GetString("")) << "Wrong entry value";
+  EXPECT_EQ("string", entry->GetString("")) << "Wrong entry value";
   EXPECT_EQ("/Shuffleboard/Tab/First/Second/Third/Fourth/Value",
-            entry.GetTopic().GetName())
+            entry->GetTopic().GetName())
       << "Entry path generated incorrectly";
 }
 
@@ -64,11 +64,11 @@ TEST(ShuffleboardInstanceTest, NestedLayoutsOop) {
   frc::ShuffleboardLayout& third = second.GetLayout("Third", "List");
   frc::ShuffleboardLayout& fourth = third.GetLayout("Fourth", "List");
   frc::SimpleWidget& widget = fourth.Add("Value", "string");
-  auto& entry = widget.GetEntry();
+  auto entry = widget.GetEntry();
 
-  EXPECT_EQ("string", entry.GetString("")) << "Wrong entry value";
+  EXPECT_EQ("string", entry->GetString("")) << "Wrong entry value";
   EXPECT_EQ("/Shuffleboard/Tab/First/Second/Third/Fourth/Value",
-            entry.GetTopic().GetName())
+            entry->GetTopic().GetName())
       << "Entry path generated incorrectly";
 }
 

wpilibcExamples/src/main/cpp/examples/ShuffleBoard/cpp/Robot.cpp

@@ -31,10 +31,10 @@ class Robot : public frc::TimedRobot {
  public:
   void RobotInit() override {
     // Add a widget titled 'Max Speed' with a number slider.
-    m_maxSpeed = &frc::Shuffleboard::GetTab("Configuration")
-                      .Add("Max Speed", 1)
-                      .WithWidget("Number Slider")
-                      .GetEntry();
+    m_maxSpeed = frc::Shuffleboard::GetTab("Configuration")
+                     .Add("Max Speed", 1)
+                     .WithWidget("Number Slider")
+                     .GetEntry();
 
     // Create a 'DriveBase' tab and add the drivetrain object to it.
     frc::ShuffleboardTab& driveBaseTab = frc::Shuffleboard::GetTab("DriveBase");