[TD]add check for Gui up

src/Mod/TechDraw/App/DrawUtil.cpp

@@ -1887,6 +1887,14 @@ std::string DrawUtil::cleanFilespecBackslash(const std::string& filespec)
     return noBackslash;
 }
 
+//! returns true if the Gui module and its event loop are active.
+bool DrawUtil::isGuiUp()
+{
+    std::string pyCommand{"import FreeCAD\nguiState = FreeCAD.GuiUp"};
+    std::string result{Base::Interpreter().runStringWithKey(pyCommand.c_str(), "guiState", "None")};
+    return  (result == "1");
+}
+
 
 //============================
 // various debugging routines.

src/Mod/TechDraw/App/DrawUtil.h

@@ -271,6 +271,7 @@ public:
 
     static std::string cleanFilespecBackslash(const std::string& filespec);
 
+    static bool isGuiUp();
 
     //debugging routines
     static void dumpVertexes(const char* text, const TopoDS_Shape& s);