regularize application startup. use Qt's command line parser support

tools/lammps-gui/main.cpp

@@ -14,28 +14,42 @@
 #include "lammpsgui.h"
 
 #include <QApplication>
+#include <QCommandLineOption>
+#include <QCommandLineParser>
+#include <QLocale>
 
 #include <cstdio>
 #include <cstring>
 
+#define stringify(x) myxstr(x)
+#define myxstr(x) #x
+
 int main(int argc, char *argv[])
 {
-    QApplication a(argc, argv);
+    Q_INIT_RESOURCE(lammpsgui);
+    QApplication app(argc, argv);
+    // enforce using the plain ASCII C locale within the GUI.
+    QLocale::setDefault(QLocale::c());
+    QCoreApplication::setOrganizationName("The LAMMPS Developers");
+    QCoreApplication::setOrganizationDomain("lammps.org");
+    QCoreApplication::setApplicationName("LAMMPS-GUI - QT" stringify(QT_VERSION_MAJOR));
+    QCoreApplication::setApplicationVersion(LAMMPS_GUI_VERSION);
+    QCommandLineParser parser;
+    parser.setApplicationDescription(
+        "\nThis is LAMMPS-GUI v" LAMMPS_GUI_VERSION "\n"
+        "\nA graphical editor for LAMMPS input files with syntax highlighting and\n"
+        "auto-completion that can run LAMMPS directly. It has built-in capabilities\n"
+        "for monitoring, visualization, plotting, and capturing console output.");
+    parser.addHelpOption();
+    parser.addVersionOption();
+    parser.addPositionalArgument("file", "The LAMMPS input file to open (optional).");
+    parser.process(app); // this removes known arguments
 
     const char *infile = nullptr;
-    if (argc > 1) {
-        infile = argv[1];
-        if ((strcmp(infile, "-help") == 0) || (strcmp(infile, "-h") == 0)) {
-            printf("This is LAMMPS-GUI version " LAMMPS_GUI_VERSION
-                   " using Qt version " QT_VERSION_STR "\n");
-            printf("Usage: %s [-h|-help|<inputfile>]\n", argv[0]);
-            return 1;
-        }
-    }
-
+    if (argc > 1) infile = argv[1];
     LammpsGui w(nullptr, infile);
     w.show();
-    return QApplication::exec();
+    return app.exec();
 }
 
 // Local Variables: