[glass] Add more widgets (#2947)

This adds the following widgets:
- Speed Controller
- Gyroscope
- Command
- Subsystem
- PIDController
- Scheduler

glass/src/libnt/native/cpp/NTGyro.cpp

@@ -0,0 +1,40 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2020 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "glass/networktables/NTGyro.h"
+
+using namespace glass;
+
+NTGyroModel::NTGyroModel(wpi::StringRef path)
+    : NTGyroModel(nt::GetDefaultInstance(), path) {}
+
+NTGyroModel::NTGyroModel(NT_Inst instance, wpi::StringRef path)
+    : m_nt(instance),
+      m_angle(m_nt.GetEntry(path + "/Value")),
+      m_name(m_nt.GetEntry(path + "/.name")),
+      m_angleData("NT_Gyro:" + path),
+      m_nameValue(path.rsplit('/').second) {
+  m_nt.AddListener(m_angle);
+  m_nt.AddListener(m_name);
+  Update();
+}
+
+void NTGyroModel::Update() {
+  for (auto&& event : m_nt.PollListener()) {
+    if (event.entry == m_angle) {
+      if (event.value && event.value->IsDouble())
+        m_angleData.SetValue(event.value->GetDouble());
+    } else if (event.entry == m_name) {
+      if (event.value && event.value->IsString())
+        m_nameValue = event.value->GetString();
+    }
+  }
+}
+
+bool NTGyroModel::Exists() {
+  return m_nt.IsConnected() && nt::GetEntryType(m_angle) != NT_UNASSIGNED;
+}