[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/RelaySimGui.cpp

@@ -0,0 +1,120 @@
+/*----------------------------------------------------------------------------*/
+/* 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 "RelaySimGui.h"
+
+#include <glass/hardware/Relay.h>
+
+#include <memory>
+#include <vector>
+
+#include <hal/Ports.h>
+#include <hal/simulation/RelayData.h>
+#include <wpigui.h>
+
+#include "HALDataSource.h"
+#include "HALSimGui.h"
+
+using namespace halsimgui;
+
+namespace {
+HALSIMGUI_DATASOURCE_BOOLEAN_INDEXED(RelayForward, "RelayFwd");
+HALSIMGUI_DATASOURCE_BOOLEAN_INDEXED(RelayReverse, "RelayRev");
+
+class RelaySimModel : public glass::RelayModel {
+ public:
+  explicit RelaySimModel(int32_t index)
+      : m_index{index}, m_forward{index}, m_reverse{index} {}
+
+  void Update() override {}
+
+  bool Exists() override {
+    return HALSIM_GetRelayInitializedForward(m_index) ||
+           HALSIM_GetRelayInitializedReverse(m_index);
+  }
+
+  glass::DataSource* GetForwardData() override {
+    return HALSIM_GetRelayInitializedForward(m_index) ? &m_forward : nullptr;
+  }
+  glass::DataSource* GetReverseData() override {
+    return HALSIM_GetRelayInitializedReverse(m_index) ? &m_reverse : nullptr;
+  }
+
+  void SetForward(bool val) override { HALSIM_SetRelayForward(m_index, val); }
+  void SetReverse(bool val) override { HALSIM_SetRelayReverse(m_index, val); }
+
+ private:
+  int32_t m_index;
+  RelayForwardSource m_forward;
+  RelayReverseSource m_reverse;
+};
+
+class RelaysSimModel : public glass::RelaysModel {
+ public:
+  RelaysSimModel() : m_models(HAL_GetNumRelayHeaders()) {}
+
+  void Update() override;
+
+  bool Exists() override { return true; }
+
+  void ForEachRelay(wpi::function_ref<void(glass::RelayModel& model, int index)>
+                        func) override;
+
+ private:
+  // indexed by channel
+  std::vector<std::unique_ptr<RelaySimModel>> m_models;
+};
+}  // namespace
+
+void RelaysSimModel::Update() {
+  for (int32_t i = 0, iend = static_cast<int32_t>(m_models.size()); i < iend;
+       ++i) {
+    auto& model = m_models[i];
+    if (HALSIM_GetRelayInitializedForward(i) ||
+        HALSIM_GetRelayInitializedReverse(i)) {
+      if (!model) {
+        model = std::make_unique<RelaySimModel>(i);
+      }
+    } else {
+      model.reset();
+    }
+  }
+}
+
+void RelaysSimModel::ForEachRelay(
+    wpi::function_ref<void(glass::RelayModel& 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);
+    }
+  }
+}
+
+static bool RelayAnyInitialized() {
+  static const int32_t num = HAL_GetNumRelayHeaders();
+  for (int32_t i = 0; i < num; ++i) {
+    if (HALSIM_GetRelayInitializedForward(i) ||
+        HALSIM_GetRelayInitializedReverse(i))
+      return true;
+  }
+  return false;
+}
+
+void RelaySimGui::Initialize() {
+  HALSimGui::halProvider.Register(
+      "Relays", RelayAnyInitialized,
+      [] { return std::make_unique<RelaysSimModel>(); },
+      [](glass::Window* win, glass::Model* model) {
+        win->SetFlags(ImGuiWindowFlags_AlwaysAutoResize);
+        win->SetDefaultPos(180, 20);
+        return glass::MakeFunctionView([=] {
+          glass::DisplayRelays(static_cast<RelaysSimModel*>(model),
+                               HALSimGui::halProvider.AreOutputsEnabled());
+        });
+      });
+}