GUI support from Python

Enables experimental support for starting the Netgen GUI from Python
directly.
To use it, just import the gui module:
> import netgen.gui

libsrc/meshing/global.cpp

@@ -27,7 +27,9 @@ namespace netgen
     global_mesh = m;
   }
   
-
+  // true if netgen was started using the netgen executable
+  // false if netgen.gui was imported from python
+  DLL_HEADER bool netgen_executable_started = false;
   
   //  Flags parameters;
   int silentflag = 0;

ng/CMakeLists.txt

@@ -11,11 +11,17 @@ if(USE_GUI)
 
     add_executable(netgen ${netgen_sources})
     target_link_libraries( netgen nglib ${ZLIB_LIBRARIES} ${LIBTOGL} ${TK_LIBRARY} ${TCL_LIBRARY} ${JPEG_LIBRARIES} ${FFMPEG_LIBRARIES} ${X11_X11_LIB} ${OCC_LIBRARIES})
+    add_library(gui SHARED ${netgen_sources} gui.cpp)
+    target_link_libraries( gui nglib ${ZLIB_LIBRARIES} ${LIBTOGL} ${TK_LIBRARY} ${TCL_LIBRARY} ${JPEG_LIBRARIES} ${FFMPEG_LIBRARIES} ${X11_X11_LIB} ${OCC_LIBRARIES})
     if(NOT WIN32)
       target_link_libraries( netgen mesh stlvis stl geom2dvis interface geom2d csg stl visual csgvis )
+      target_link_libraries( gui mesh stlvis stl geom2dvis interface geom2d csg stl visual csgvis )
     endif(NOT WIN32)
 
     install(TARGETS netgen    ${ng_install_dir})
+    install(TARGETS gui  DESTINATION ${PYTHON_PACKAGES_INSTALL_DIR}/netgen)
+    set_target_properties( gui PROPERTIES PREFIX "") # name output file gui.so instead of libgui.so
+
     if(APPLE)
         set_target_properties(netgen PROPERTIES OUTPUT_NAME netgen)
     endif(APPLE)

ng/gui.cpp

@@ -0,0 +1,222 @@
+#include <mystdlib.h> 
+#include <inctcl.hpp>
+#include <meshing.hpp>
+
+#include "../libsrc/interface/writeuser.hpp"
+#include <pybind11/pybind11.h>
+
+namespace netgen
+{
+  DLL_HEADER extern Flags parameters;
+  DLL_HEADER extern bool netgen_executable_started;
+  DLL_HEADER extern int printmessage_importance;
+}
+
+using netgen::parameters;
+using netgen::ngdir;
+using netgen::verbose;
+using netgen::Array;
+using netgen::RegisterUserFormats;
+
+extern "C" int Ng_ServerSocketManagerInit (int port);
+extern "C" int Ng_ServerSocketManagerRun (void);
+ 
+int Tcl_AppInit(Tcl_Interp * interp);
+
+extern bool nodisplay;
+extern bool shellmode;
+
+void main_gui()
+{
+  if(netgen::netgen_executable_started)
+      return;
+
+  if ( netgen::id == 0 )
+    {
+      cout << "NETGEN-" << PACKAGE_VERSION << endl;
+      
+      cout << "Developed by Joachim Schoeberl at" << endl
+	   << "2010-xxxx Vienna University of Technology" << endl
+	   << "2006-2010 RWTH Aachen University" << endl
+           << "1996-2006 Johannes Kepler University Linz" << endl;
+      
+#ifdef OCCGEOMETRY
+      cout << "Including OpenCascade geometry kernel" << endl;
+#endif
+      
+#ifdef ACIS
+      cout << "Including ACIS geometry kernel" << endl;
+#endif
+
+#ifdef DEBUG
+      cout << "You are running the debug version !" << endl;
+#endif
+
+
+    }
+
+//   netgen::h_argc = argc;
+//   netgen::h_argv = argv;
+
+  if (getenv ("NETGENDIR") && strlen (getenv ("NETGENDIR")))
+    ngdir = getenv ("NETGENDIR");
+  else
+    ngdir = ".";
+  
+  verbose = parameters.GetDefineFlag ("V");
+
+  if (verbose)
+    cout << "NETGENDIR = " << ngdir << endl;
+  
+
+  if ( netgen::id == 0 )
+    {
+      if (parameters.StringFlagDefined ("testout"))      
+        netgen::testout = new ofstream (parameters.GetStringFlag ("testout", "test.out"));
+
+
+      if(parameters.GetDefineFlag("batchmode"))
+        nodisplay = true;
+
+    
+      if(parameters.GetDefineFlag("shellmode"))
+        {
+          nodisplay = true;
+          shellmode = true;
+        }
+
+      Tcl_FindExecutable(NULL);
+
+      // initialize application
+      Tcl_Interp * myinterp = Tcl_CreateInterp ();
+      if (Tcl_AppInit (myinterp) == TCL_ERROR)
+        {
+          cerr << "Exit Netgen due to initialization problem" << endl;
+          exit (1);
+        }
+
+
+
+      // parse tcl-script
+      int errcode;
+
+      bool internaltcl = false;
+      if (shellmode)
+        internaltcl = false;
+  
+      if (verbose)
+        {
+          cout << "Tcl header version = " << TCL_PATCH_LEVEL << endl;
+          Tcl_Eval (myinterp, "puts \"Tcl runtime version = [info patchlevel] \";");
+        }
+
+      if (parameters.GetDefineFlag ("internaltcl"))
+        internaltcl=true;
+      if (parameters.GetDefineFlag ("externaltcl"))
+        internaltcl=false;
+
+ 
+
+      if (internaltcl)
+        {
+          if (verbose)
+            cout << "using internal Tcl-script" << endl;
+      
+          // connect to one string 
+          extern const char * ngscript[];
+          const char ** hcp = ngscript;
+          int len = 0;
+          while (*hcp)
+            len += strlen (*hcp++); 
+
+          char * tr1 = new char[len+1];
+          *tr1 = 0;
+          hcp = ngscript;
+      
+          char * tt1 = tr1;
+          while (*hcp)
+            {
+              strcat (tt1, *hcp); 
+              tt1 += strlen (*hcp++);
+            }
+      
+          errcode = Tcl_Eval (myinterp, tr1);
+          delete [] tr1;
+        }
+
+      else
+
+        {
+          string startfile = ngdir + "/ng.tcl";
+      
+          if (verbose)
+            cout << "Load Tcl-script from " << startfile << endl;
+      
+          errcode = Tcl_EvalFile (myinterp, (char*)startfile.c_str());
+        }
+
+      if (errcode)
+        {
+          cout << "Error in Tcl-Script:" << endl;
+          // cout << "result = " << myinterp->result << endl;
+          cout << "result = " << Tcl_GetStringResult (myinterp) << endl;
+          // cout << "in line " << myinterp->errorLine << endl;
+
+          cout << "\nMake sure to set environment variable NETGENDIR to directory containing ng.tcl" << endl;
+          exit (1);
+        }
+
+
+      // lookup user file formats and insert into format list:
+      Array<const char*> userformats;
+      Array<const char*> extensions;
+      RegisterUserFormats (userformats, extensions);
+
+      ostringstream fstr;
+      
+      tcl_const char * exportft = Tcl_GetVar (myinterp, "exportfiletype", 0);
+      for (int i = 1; i <= userformats.Size(); i++)
+	{
+	  fstr << ".ngmenu.file.filetype add radio -label \"" 
+	       << userformats.Get(i) << "\" -variable exportfiletype\n";
+	  fstr << "lappend meshexportformats { {" << userformats.Get(i) << "} {" << extensions.Get(i) << "} }\n";
+	}
+
+      Tcl_Eval (myinterp, (char*)fstr.str().c_str());
+      Tcl_SetVar (myinterp, "exportfiletype", exportft, 0);
+
+
+      // start event-loop
+      Tk_MainLoop();
+      Tcl_DeleteInterp (myinterp); 
+//       Tcl_Exit(0);
+    }
+}
+
+
+
+extern "C" int Ng_Init (Tcl_Interp * interp);
+extern "C" int Ng_Vis_Init (Tcl_Interp * interp);
+
+extern "C" void Ng_TclCmd(string);
+
+struct GuiThread {
+    std::thread t;
+    ~GuiThread() {
+        Ng_TclCmd(".ngmenu.file invoke \"Quit\";");
+        if(netgen::printmessage_importance>2)
+          cout << "waiting for GUI to finish..." << endl;
+        t.join();
+    }
+};
+
+static GuiThread gui_thread;
+
+PYBIND11_PLUGIN(gui) {
+  pybind11::module m("gui", "pybind gui");
+    gui_thread.t = std::thread([]() 
+                {
+                  main_gui();
+                });
+  return m.ptr();
+}

ng/ngappinit.cpp

@@ -34,6 +34,7 @@ namespace netgen
 namespace netgen
 {
   Flags parameters;
+  DLL_HEADER extern bool netgen_executable_started;
 }
  
 
@@ -70,6 +71,7 @@ bool shellmode = false;
 
 int main(int argc, char ** argv)
 {
+  netgen::netgen_executable_started = true;
 
 #ifdef PARALLEL
   int mpi_required = MPI_THREAD_MULTIPLE;