[glass] Add more widgets (#2947)

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

glass/src/lib/native/cpp/hardware/SpeedController.cpp

@@ -0,0 +1,36 @@
+/*----------------------------------------------------------------------------*/
+/* 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/hardware/SpeedController.h"
+
+#include <imgui.h>
+
+#include "glass/Context.h"
+#include "glass/DataSource.h"
+
+using namespace glass;
+
+void glass::DisplaySpeedController(SpeedControllerModel* m) {
+  // Get duty cycle data from the model and do not display anything if the data
+  // is null.
+  auto dc = m->GetPercentData();
+  if (!dc || !m->Exists()) {
+    ImGui::PushStyleColor(ImGuiCol_Text, IM_COL32(96, 96, 96, 255));
+    ImGui::Text("Unknown SpeedController");
+    ImGui::PopStyleColor();
+    return;
+  }
+
+  // Add button to zero output.
+  if (ImGui::Button("Zero")) m->SetPercent(0.0);
+  ImGui::SameLine();
+
+  // Display a slider for the data.
+  float value = dc->GetValue();
+  ImGui::SetNextItemWidth(ImGui::GetFontSize() * 8);
+  if (dc->SliderFloat("% Output", &value, -1.0f, 1.0f)) m->SetPercent(value);
+}