Add timing window to simulation GUI

This shows the FPGA time and notifier timing, and has buttons to
start/pause/step the simulation.

The GUI also pauses DS new data notifications when paused.  This could be
done globally instead by blocking NotifyNewData at the HAL level?

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

@@ -14,6 +14,7 @@
 #include <imgui.h>
 #include <imgui_internal.h>
 #include <mockdata/DriverStationData.h>
+#include <mockdata/MockHooks.h>
 #include <wpi/Format.h>
 #include <wpi/SmallString.h>
 #include <wpi/StringRef.h>
@@ -328,7 +329,7 @@ static void DriverStationExecute() {
 
   // Send new data every 20 ms (may be slower depending on GUI refresh rate)
   static double lastNewDataTime = 0.0;
-  if ((curTime - lastNewDataTime) > 0.02) {
+  if ((curTime - lastNewDataTime) > 0.02 && !HALSIM_IsTimingPaused()) {
     lastNewDataTime = curTime;
     HALSIM_NotifyDriverStationNewData();
   }
@@ -367,7 +368,7 @@ static void DisplayFMS() {
                          ImGuiInputTextFlags_EnterReturnsTrue)) {
     HALSIM_SetDriverStationMatchTime(matchTime);
     startMatchTime = curTime - matchTime;
-  } else if (!HALSIM_GetDriverStationEnabled()) {
+  } else if (!HALSIM_GetDriverStationEnabled() || HALSIM_IsTimingPaused()) {
     startMatchTime = curTime - matchTime;
   } else if (matchTimeEnabled) {
     HALSIM_SetDriverStationMatchTime(curTime - startMatchTime);

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

@@ -0,0 +1,60 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 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 "TimingGui.h"
+
+#include <cstdio>
+#include <cstring>
+#include <vector>
+
+#include <hal/HALBase.h>
+#include <imgui.h>
+#include <mockdata/MockHooks.h>
+#include <mockdata/NotifierData.h>
+
+#include "HALSimGui.h"
+
+using namespace halsimgui;
+
+static void DisplayTiming() {
+  int32_t status = 0;
+  uint64_t curTime = HAL_GetFPGATime(&status);
+
+  if (ImGui::Button("Run")) HALSIM_ResumeTiming();
+  ImGui::SameLine();
+  if (ImGui::Button("Pause")) HALSIM_PauseTiming();
+  ImGui::SameLine();
+  ImGui::PushButtonRepeat(true);
+  if (ImGui::Button("Step")) {
+    HALSIM_PauseTiming();
+    uint64_t nextTimeout = HALSIM_GetNextNotifierTimeout();
+    if (nextTimeout != UINT64_MAX) HALSIM_StepTiming(nextTimeout - curTime);
+  }
+  ImGui::PopButtonRepeat();
+  ImGui::PushItemWidth(ImGui::GetFontSize() * 4);
+  ImGui::LabelText("FPGA Time", "%.3f", curTime / 1000000.0);
+  ImGui::PopItemWidth();
+
+  static std::vector<HALSIM_NotifierInfo> notifiers;
+  int32_t num = HALSIM_GetNotifierInfo(notifiers.data(), notifiers.size());
+  if (static_cast<uint32_t>(num) > notifiers.size()) {
+    notifiers.resize(num);
+    HALSIM_GetNotifierInfo(notifiers.data(), notifiers.size());
+  }
+  if (num > 0) ImGui::Separator();
+  ImGui::PushItemWidth(ImGui::GetFontSize() * 4);
+  for (int32_t i = 0; i < num; ++i)
+    ImGui::LabelText(notifiers[i].name, "%.3f",
+                     notifiers[i].timeout / 1000000.0);
+  ImGui::PopItemWidth();
+}
+
+void TimingGui::Initialize() {
+  HALSimGui::AddWindow("Timing", DisplayTiming,
+                       ImGuiWindowFlags_AlwaysAutoResize);
+  HALSimGui::SetDefaultWindowPos("Timing", 5, 150);
+}

simulation/halsim_gui/src/main/native/cpp/TimingGui.h

@@ -0,0 +1,17 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+namespace halsimgui {
+
+class TimingGui {
+ public:
+  static void Initialize();
+};
+
+}  // namespace halsimgui

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

@@ -23,6 +23,7 @@
 #include "RoboRioGui.h"
 #include "SimDeviceGui.h"
 #include "SolenoidGui.h"
+#include "TimingGui.h"
 
 using namespace halsimgui;
 
@@ -45,6 +46,7 @@ __declspec(dllexport)
   HALSimGui::Add(RoboRioGui::Initialize);
   HALSimGui::Add(SimDeviceGui::Initialize);
   HALSimGui::Add(SolenoidGui::Initialize);
+  HALSimGui::Add(TimingGui::Initialize);
 
   wpi::outs() << "Simulator GUI Initializing.\n";
   if (!HALSimGui::Initialize()) return 0;