[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/PWMSimGui.cpp

@@ -0,0 +1,119 @@
+/*----------------------------------------------------------------------------*/
+/* 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 "PWMSimGui.h"
+
+#include <glass/hardware/PWM.h>
+
+#include <memory>
+#include <vector>
+
+#include <hal/Ports.h>
+#include <hal/simulation/AddressableLEDData.h>
+#include <hal/simulation/PWMData.h>
+
+#include "HALDataSource.h"
+#include "HALSimGui.h"
+
+using namespace halsimgui;
+
+namespace {
+HALSIMGUI_DATASOURCE_DOUBLE_INDEXED(PWMSpeed, "PWM");
+
+class PWMSimModel : public glass::PWMModel {
+ public:
+  explicit PWMSimModel(int32_t index) : m_index{index}, m_speed{m_index} {}
+
+  void Update() override {}
+
+  bool Exists() override { return HALSIM_GetPWMInitialized(m_index); }
+
+  void SetAddressableLED(int led) { m_led = led; }
+  int GetAddressableLED() const override { return m_led; }
+
+  glass::DataSource* GetSpeedData() override { return &m_speed; }
+
+  void SetSpeed(double val) override { HALSIM_SetPWMSpeed(m_index, val); }
+
+ private:
+  int32_t m_index;
+  int m_led = -1;
+  PWMSpeedSource m_speed;
+};
+
+class PWMsSimModel : public glass::PWMsModel {
+ public:
+  PWMsSimModel() : m_sources(HAL_GetNumPWMChannels()) {}
+
+  void Update() override;
+
+  bool Exists() override { return true; }
+
+  void ForEachPWM(
+      wpi::function_ref<void(glass::PWMModel& model, int index)> func) override;
+
+ private:
+  // indexed by channel
+  std::vector<std::unique_ptr<PWMSimModel>> m_sources;
+};
+}  // namespace
+
+void PWMsSimModel::Update() {
+  const int32_t numPWM = m_sources.size();
+  for (int32_t i = 0; i < numPWM; ++i) {
+    auto& model = m_sources[i];
+    if (HALSIM_GetPWMInitialized(i)) {
+      if (!model) {
+        model = std::make_unique<PWMSimModel>(i);
+      }
+      model->SetAddressableLED(-1);
+    } else {
+      model.reset();
+    }
+  }
+
+  static const int32_t numLED = HAL_GetNumAddressableLEDs();
+  for (int32_t i = 0; i < numLED; ++i) {
+    if (HALSIM_GetAddressableLEDInitialized(i)) {
+      int32_t channel = HALSIM_GetAddressableLEDOutputPort(i);
+      if (channel >= 0 && channel < numPWM && m_sources[channel])
+        m_sources[channel]->SetAddressableLED(i);
+    }
+  }
+}
+
+void PWMsSimModel::ForEachPWM(
+    wpi::function_ref<void(glass::PWMModel& model, int index)> func) {
+  const int32_t numPWM = m_sources.size();
+  for (int32_t i = 0; i < numPWM; ++i) {
+    if (auto model = m_sources[i].get()) {
+      func(*model, i);
+    }
+  }
+}
+
+static bool PWMsAnyInitialized() {
+  static const int32_t num = HAL_GetNumPWMChannels();
+  for (int32_t i = 0; i < num; ++i) {
+    if (HALSIM_GetPWMInitialized(i)) return true;
+  }
+  return false;
+}
+
+void PWMSimGui::Initialize() {
+  HALSimGui::halProvider.Register(
+      "PWM Outputs", PWMsAnyInitialized,
+      [] { return std::make_unique<PWMsSimModel>(); },
+      [](glass::Window* win, glass::Model* model) {
+        win->SetFlags(ImGuiWindowFlags_AlwaysAutoResize);
+        win->SetDefaultPos(910, 20);
+        return glass::MakeFunctionView([=] {
+          glass::DisplayPWMs(static_cast<PWMsSimModel*>(model),
+                             HALSimGui::halProvider.AreOutputsEnabled());
+        });
+      });
+}