Simplify backtrace output

This makes backtrace readable

src/utils/BacktraceManager.cpp

@@ -25,7 +25,7 @@ BacktraceManager::BacktraceManager()
   char** ptr = backtrace_symbols(buffer, ret);
 
   for (int i = 2; i < ret; ++i) {
-    m_lines.push_back(ptr[i]);
+    m_stack_lines.push_back(ptr[i]);
   }
 
   free(ptr);
@@ -35,27 +35,35 @@ std::ostream&
 operator<<(std::ostream& os, const BacktraceManager& btm)
 {
   if (BacktraceManager::s_show) {
-    const std::vector<std::string>& lines = btm.m_lines;
+    const std::vector<std::string>& stack_lines = btm.m_stack_lines;
 
     const std::regex mangled_function(R"%(\(.*\+)%");
-    const int width = std::log10(lines.size()) + 1;
+    const int width = std::log10(stack_lines.size()) + 1;
 
-    for (size_t i_line = 0; i_line < lines.size(); ++i_line) {
-      const auto& line = lines[i_line];
-      os << rang::fg::green << "[" << std::setw(width) << i_line + 1 << '/' << lines.size() << "] " << rang::fg::reset;
+    for (size_t i_stack_line = 0; i_stack_line < stack_lines.size(); ++i_stack_line) {
+      const size_t i_line    = stack_lines.size() - i_stack_line - 1;
+      const auto& stack_line = stack_lines[i_line];
+      os << rang::fg::green << "[" << std::setw(width) << i_line + 1 << '/' << stack_lines.size() << "] "
+         << rang::fg::reset;
       std::smatch matchex;
-      if (std::regex_search(line, matchex, mangled_function)) {
+      if (std::regex_search(stack_line, matchex, mangled_function)) {
         std::string prefix   = matchex.prefix().str();
-        std::string function = line.substr(matchex.position() + 1, matchex.length() - 2);
+        std::string function = stack_line.substr(matchex.position() + 1, matchex.length() - 2);
         std::string suffix   = matchex.suffix().str();
 
-        os << prefix << '(';
+        os << prefix << '\n';
+        os << std::setw(5 + 2 * width) << "from " << '(';
         if (function.size() > 0) {
-          os << rang::style::bold << demangle(function) << rang::style::reset;
+          std::string function_full_name = demangle(function);
+          if (function_full_name.size() > 80) {
+            function_full_name.resize(75);
+            function_full_name += "[...]";
+          }
+          os << rang::style::bold << function_full_name << rang::style::reset;
         }
         os << '+' << suffix << '\n';
       } else {
-        os << line << '\n';
+        os << stack_line << '\n';
       }
     }
   } else {

src/utils/BacktraceManager.hpp

@@ -8,7 +8,7 @@ class BacktraceManager
 {
  private:
   static bool s_show;
-  std::vector<std::string> m_lines;
+  std::vector<std::string> m_stack_lines;
 
  public:
   static void setShow(bool show_backtrace);