[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.

glass/src/lib/native/cpp/WindowManager.cpp

@@ -0,0 +1,107 @@
+/*----------------------------------------------------------------------------*/
+/* 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 "glass/WindowManager.h"
+
+#include <algorithm>
+
+#include <wpi/StringRef.h>
+#include <wpi/raw_ostream.h>
+#include <wpigui.h>
+
+using namespace glass;
+
+WindowManager::WindowManager(const wpi::Twine& iniName)
+    : m_iniSaver{iniName, this} {}
+
+// read/write open state to ini file
+void* WindowManager::IniSaver::IniReadOpen(const char* name) {
+  return m_manager->GetOrAddWindow(name, true);
+}
+
+void WindowManager::IniSaver::IniReadLine(void* entry, const char* lineStr) {
+  static_cast<Window*>(entry)->IniReadLine(lineStr);
+}
+
+void WindowManager::IniSaver::IniWriteAll(ImGuiTextBuffer* out_buf) {
+  const char* typeName = GetTypeName();
+  for (auto&& window : m_manager->m_windows) {
+    window->IniWriteAll(typeName, out_buf);
+  }
+}
+
+Window* WindowManager::AddWindow(wpi::StringRef id,
+                                 wpi::unique_function<void()> display) {
+  auto win = GetOrAddWindow(id, false);
+  if (!win) return nullptr;
+  if (win->HasView()) {
+    wpi::errs() << "GUI: ignoring duplicate window '" << id << "'\n";
+    return nullptr;
+  }
+  win->SetView(MakeFunctionView(std::move(display)));
+  return win;
+}
+
+Window* WindowManager::AddWindow(wpi::StringRef id,
+                                 std::unique_ptr<View> view) {
+  auto win = GetOrAddWindow(id, false);
+  if (!win) return nullptr;
+  if (win->HasView()) {
+    wpi::errs() << "GUI: ignoring duplicate window '" << id << "'\n";
+    return nullptr;
+  }
+  win->SetView(std::move(view));
+  return win;
+}
+
+Window* WindowManager::GetOrAddWindow(wpi::StringRef id, bool duplicateOk) {
+  // binary search
+  auto it = std::lower_bound(
+      m_windows.begin(), m_windows.end(), id,
+      [](const auto& elem, wpi::StringRef s) { return elem->GetId() < s; });
+  if (it != m_windows.end() && (*it)->GetId() == id) {
+    if (!duplicateOk) {
+      wpi::errs() << "GUI: ignoring duplicate window '" << id << "'\n";
+      return nullptr;
+    }
+    return it->get();
+  }
+  // insert before (keeps sort)
+  return m_windows.emplace(it, std::make_unique<Window>(id))->get();
+}
+
+Window* WindowManager::GetWindow(wpi::StringRef id) {
+  // binary search
+  auto it = std::lower_bound(
+      m_windows.begin(), m_windows.end(), id,
+      [](const auto& elem, wpi::StringRef s) { return elem->GetId() < s; });
+  if (it == m_windows.end() || (*it)->GetId() != id) return nullptr;
+  return it->get();
+}
+
+void WindowManager::GlobalInit() {
+  wpi::gui::AddInit([this] { m_iniSaver.Initialize(); });
+  wpi::gui::AddWindowScaler([this](float scale) {
+    // scale default window positions
+    for (auto&& window : m_windows) {
+      window->ScaleDefault(scale);
+    }
+  });
+  wpi::gui::AddLateExecute([this] { DisplayWindows(); });
+}
+
+void WindowManager::DisplayMenu() {
+  for (auto&& window : m_windows) {
+    window->DisplayMenuItem();
+  }
+}
+
+void WindowManager::DisplayWindows() {
+  for (auto&& window : m_windows) {
+    window->Display();
+  }
+}