Move help message out of AppInit2

- Solves #1278, attempts to address #1049
- Removes \t's from help message that are removed afterwards anyway
- Moves UI-specific command-line options help to UI code
- Moves "-detachdb" out of #ifdef USE_UPNP

src/qt/bitcoin.cpp

@@ -129,6 +129,53 @@ static void handleRunawayException(std::exception *e)
     exit(1);
 }
 
+/** Help message for Bitcoin-Qt, shown with --help. */
+class HelpMessageBox: public QMessageBox
+{
+public:
+    HelpMessageBox(QWidget *parent = 0);
+
+    void exec();
+private:
+    QString header;
+    QString coreOptions;
+    QString uiOptions;
+};
+#include <QSpacerItem>
+#include <QGridLayout>
+HelpMessageBox::HelpMessageBox(QWidget *parent):
+    QMessageBox(parent)
+{
+    header = tr("Bitcoin-Qt") + " " + tr("version") + " " +
+            QString::fromStdString(FormatFullVersion()) + "\n\n" +
+        tr("Usage:") + "\n" +
+          "  bitcoin-qt [options]                     " + "\n";
+    coreOptions = QString::fromStdString(HelpMessage());
+    uiOptions = tr("UI options") + ":\n" +
+            "  -lang=<lang>           " + tr("Set language, for example \"de_DE\" (default: system locale)") + "\n" +
+            "  -min                   " + tr("Start minimized") + "\n" +
+            "  -splash                " + tr("Show splash screen on startup (default: 1)") + "\n";
+
+    setWindowTitle(tr("Bitcoin-Qt"));
+    setTextFormat(Qt::PlainText);
+    // setMinimumWidth is ignored for QMessageBox so put in nonbreaking spaces to make it wider.
+    QChar em_space(0x2003);
+    setText(header + QString(em_space).repeated(40));
+    setDetailedText(coreOptions + "\n" + uiOptions);
+}
+
+void HelpMessageBox::exec()
+{
+#if defined(WIN32)
+    // On windows, show a message box, as there is no stderr in windowed applications
+    QMessageBox::exec();
+#else
+    // On other operating systems, the expected action is to print the message to the console.
+    QString strUsage = header + "\n" + coreOptions + "\n" + uiOptions;
+    fprintf(stderr, "%s", strUsage.toStdString().c_str());
+#endif
+}
+
 #ifdef WIN32
 #define strncasecmp strnicmp
 #endif
@@ -218,6 +265,15 @@ int main(int argc, char *argv[])
     if (translator.load(lang_territory, ":/translations/"))
         app.installTranslator(&translator);
 
+    // Show help message immediately after parsing command-line options (for "-lang") and setting locale,
+    // but before showing splash screen.
+    if (mapArgs.count("-?") || mapArgs.count("--help"))
+    {
+        HelpMessageBox help;
+        help.exec();
+        return 1;
+    }
+
     QSplashScreen splash(QPixmap(":/images/splash"), 0);
     if (GetBoolArg("-splash", true) && !GetBoolArg("-min"))
     {
@@ -238,7 +294,7 @@ int main(int argc, char *argv[])
 
         BitcoinGUI window;
         guiref = &window;
-        if(AppInit2(argc, argv))
+        if(AppInit2())
         {
             {
                 // Put this in a block, so that the Model objects are cleaned up before