[glass] Add glass: an application for display of robot data

This reuses many pieces of the current simulation GUI.  The common pieces have
been refactored into the libglass library.

The libglass library is designed to be usable for other standalone data
visualization applications (e.g. viewing data logs).

The name "glass" comes from "glass cockpit", as the application features
several multi-function displays that can be adjusted to display robot
information as needed.

simulation/halsim_gui/src/main/native/cpp/AnalogOutputSimGui.cpp

@@ -0,0 +1,96 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019-2020 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 "AnalogOutputSimGui.h"
+
+#include <glass/hardware/AnalogOutput.h>
+#include <glass/other/DeviceTree.h>
+
+#include <memory>
+#include <vector>
+
+#include <hal/Ports.h>
+#include <hal/simulation/AnalogOutData.h>
+
+#include "HALDataSource.h"
+#include "HALSimGui.h"
+#include "SimDeviceGui.h"
+
+using namespace halsimgui;
+
+namespace {
+HALSIMGUI_DATASOURCE_DOUBLE_INDEXED(AnalogOutVoltage, "AOut");
+
+class AnalogOutputSimModel : public glass::AnalogOutputModel {
+ public:
+  explicit AnalogOutputSimModel(int32_t index)
+      : m_index{index}, m_voltageData{m_index} {}
+
+  void Update() override {}
+
+  bool Exists() override { return HALSIM_GetAnalogOutInitialized(m_index); }
+
+  glass::DataSource* GetVoltageData() override { return &m_voltageData; }
+
+  void SetVoltage(double val) override {
+    HALSIM_SetAnalogOutVoltage(m_index, val);
+  }
+
+ private:
+  int32_t m_index;
+  AnalogOutVoltageSource m_voltageData;
+};
+
+class AnalogOutputsSimModel : public glass::AnalogOutputsModel {
+ public:
+  AnalogOutputsSimModel() : m_models(HAL_GetNumAnalogOutputs()) {}
+
+  void Update() override;
+
+  bool Exists() override { return true; }
+
+  void ForEachAnalogOutput(
+      wpi::function_ref<void(glass::AnalogOutputModel& model, int index)> func)
+      override;
+
+ private:
+  // indexed by channel
+  std::vector<std::unique_ptr<AnalogOutputSimModel>> m_models;
+};
+}  // namespace
+
+void AnalogOutputsSimModel::Update() {
+  for (int32_t i = 0, iend = static_cast<int32_t>(m_models.size()); i < iend;
+       ++i) {
+    auto& model = m_models[i];
+    if (HALSIM_GetAnalogOutInitialized(i)) {
+      if (!model) {
+        model = std::make_unique<AnalogOutputSimModel>(i);
+      }
+    } else {
+      model.reset();
+    }
+  }
+}
+
+void AnalogOutputsSimModel::ForEachAnalogOutput(
+    wpi::function_ref<void(glass::AnalogOutputModel& model, int index)> func) {
+  for (int32_t i = 0, iend = static_cast<int32_t>(m_models.size()); i < iend;
+       ++i) {
+    if (auto model = m_models[i].get()) {
+      func(*model, i);
+    }
+  }
+}
+
+void AnalogOutputSimGui::Initialize() {
+  SimDeviceGui::GetDeviceTree().Add(
+      std::make_unique<AnalogOutputsSimModel>(), [](glass::Model* model) {
+        glass::DisplayAnalogOutputsDevice(
+            static_cast<AnalogOutputsSimModel*>(model));
+      });
+}