message: Add tooltip for event filter text field
diff: @@ -754,8 +754,6 @@ const char *filter_get_keyval_func( const trace_event_t *event, const char *name
  return "";
  }
  -const char *te_compile2( const char *expression, tdop_get_key_func &get_key_func, tdop_get_keyval_func &get_keyval_func );
  -
  bool TraceWin::render()
  {
  ImGui::SetNextWindowSize( ImVec2( 800, 600 ), ImGuiSetCond_FirstUseEver );
  @@ -930,6 +928,24 @@ bool TraceWin::render()
  }
  }
  + if ( ImGui::IsItemHovered() )
  + {
  + std::string tooltip;
  +
  + tooltip += "Event Filter\n\n";
  + tooltip += "Vars: Any field in Info column plus:\n";
  + tooltip += " $name, $comm, $user_comm, $id, $pid, $ts\n";
  + tooltip += "Operators: &&, ||, !=, =, >, >=, <, <=, =~\n\n";
  + tooltip += "Examples:\n";
  + tooltip += " $pid = 4615\n";
  + tooltip += " $ts >= 11.1 && $ts < 12.5\n";
  + tooltip += " $ring_name = 0xffff971e9aa6bdd0\n";
  + tooltip += " $buf =~ \"[Compositor] Warp\"\n";
  + tooltip += " ( $timeline = gfx ) && ( $id < 10 || $id > 100 )";
  +
  + ImGui::SetTooltip( "%s", tooltip.c_str() );
  + }
  +
  ImGui::SameLine();
  if ( ImGui::SmallButton( "Clear Filter" ) )
  m_filtered_events.clear();
  