[glass] Add NetworkTables Log window (#2997)

This moves NetworkTable log messages out of the console (which is hidden on some platforms).

glass/src/lib/native/cpp/other/Log.cpp

@@ -0,0 +1,70 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "glass/other/Log.h"
+
+#include <imgui.h>
+#include <wpi/raw_ostream.h>
+
+using namespace glass;
+
+void LogData::Clear() {
+  m_buf.clear();
+  m_lineOffsets.clear();
+  m_lineOffsets.push_back(0);
+}
+
+void LogData::Append(const wpi::Twine& msg) {
+  if (m_lineOffsets.size() >= m_maxLines) {
+    Clear();
+  }
+
+  size_t oldSize = m_buf.size();
+  wpi::raw_vector_ostream os{m_buf};
+  msg.print(os);
+  for (size_t newSize = m_buf.size(); oldSize < newSize; ++oldSize) {
+    if (m_buf[oldSize] == '\n') {
+      m_lineOffsets.push_back(oldSize + 1);
+    }
+  }
+}
+
+void glass::DisplayLog(LogData* data, bool autoScroll) {
+  if (data->m_buf.empty()) {
+    return;
+  }
+  ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(0, 0));
+  const char* buf = data->m_buf.data();
+  const char* bufEnd = buf + data->m_buf.size();
+  ImGuiListClipper clipper;
+  clipper.Begin(data->m_lineOffsets.size());
+  while (clipper.Step()) {
+    for (size_t lineNum = clipper.DisplayStart;
+         lineNum < static_cast<size_t>(clipper.DisplayEnd); lineNum++) {
+      const char* lineStart = buf + data->m_lineOffsets[lineNum];
+      const char* lineEnd = (lineNum + 1 < data->m_lineOffsets.size())
+                                ? (buf + data->m_lineOffsets[lineNum + 1] - 1)
+                                : bufEnd;
+      ImGui::TextUnformatted(lineStart, lineEnd);
+    }
+  }
+  clipper.End();
+  ImGui::PopStyleVar();
+
+  if (autoScroll && ImGui::GetScrollY() >= ImGui::GetScrollMaxY()) {
+    ImGui::SetScrollHereY(1.0f);
+  }
+}
+
+void LogView::Display() {
+  if (ImGui::BeginPopupContextItem()) {
+    ImGui::Checkbox("Auto-scroll", &m_autoScroll);
+    if (ImGui::Selectable("Clear")) {
+      m_data->Clear();
+    }
+    ImGui::EndPopup();
+  }
+
+  DisplayLog(m_data, m_autoScroll);
+}