try to find client executable in same directory as argv0

this amkes it easier to ship bundles (e.g. gmsh+getdp)

Common/CommandLine.cpp

@@ -268,6 +268,7 @@ void GetOptions(int argc, char *argv[])
 
 #if defined(HAVE_PARSER)
   if(argc && argv){
+    CTX::instance()->argv0 = std::string(argv[0]);
     // parse session and option file (if argc/argv is not provided skip this
     // step: this is usually what is expected when using Gmsh as a library)
     ParseFile(CTX::instance()->homeDir + CTX::instance()->sessionFileName, true);

Common/Context.h

@@ -79,6 +79,7 @@ class CTX {
   std::string bgmFileName, outputFileName, defaultFileName, tmpFileName;
   std::string sessionFileName, optionsFileName, errorFileName;
   std::string meshStatReportFileName;
+  std::string argv0;
   // the home directory
   std::string homeDir;
   // file history

Fltk/onelabGroup.cpp

@@ -11,6 +11,7 @@
 typedef unsigned long intptr_t;
 #endif
 
+#include <ctype.h>
 #include "GmshMessage.h"
 #include "onelab.h"
 #include "gmshLocalNetworkClient.h"
@@ -864,20 +865,47 @@ static void onelab_choose_executable_cb(Fl_Widget *w, void *data)
 #if defined(WIN32)
   pattern += ".exe";
 #endif
-  const char *old = 0;
-  if(!c->getExecutable().empty()) old = c->getExecutable().c_str();
 
-  if(!w){
-    const char *old = fl_close;
+  std::string exe = "";
+
+  if(!w){ // we entered here automatically because no executable is given
+
+    // try to find an executable automatically (this is really useful for
+    // beginners)
+    if(CTX::instance()->argv0.size()){
+      std::vector<std::string> split = SplitFileName(CTX::instance()->argv0);
+      std::string name = c->getName();
+      for(unsigned int i = 0; i < name.size(); i++)
+        name[i] = tolower(name[i]);
+      std::string path = split[0] + name;
+#if defined(WIN32)
+      path += ".exe";
+#endif
+      if(!StatFile(path)){
+        exe = path;
+        Msg::Info("Automatically found %s executable: %s", c->getName().c_str(),
+                  exe.c_str());
+      }
+    }
+
+    if(exe.empty()){
+      const char *o = fl_close;
       fl_close = "OK";
       fl_message("This appears to be the first time you are trying to run %s.\n\n"
                  "Please select the path to the executable.", c->getName().c_str());
-    fl_close = old;
+      fl_close = o;
+    }
   }
 
+  if(exe.empty()){
+    const char *old = 0;
+    if(c->getExecutable().size()) old = c->getExecutable().c_str();
     std::string title = "Choose location of " + c->getName() + " executable";
-  if(fileChooser(FILE_CHOOSER_SINGLE, title.c_str(), pattern.c_str(), old)){
-    std::string exe = fileChooserGetName(1);
+    if(fileChooser(FILE_CHOOSER_SINGLE, title.c_str(), pattern.c_str(), old))
+      exe = fileChooserGetName(1);
+  }
+
+  if(exe.size()){
     c->setExecutable(exe);
     if(c->getIndex() >= 0 && c->getIndex() < 5)
       opt_solver_executable(c->getIndex(), GMSH_SET, exe);