Set console code page to CP_UTF8 on Windows if supported.

Previously, we enforced code page 850 for all console input and output,
which breaks with non-western scripts. Since more recent Windows shells
are able to display Unicode properly, this patch now enforces UTF-8 and
falls back to code page 850 only if UTF-8 is unsupported.

Resolves #3049.

Author: phoerious

src/cli/TextStream.cpp

@@ -19,6 +19,9 @@
 
 #include <QProcessEnvironment>
 #include <QTextCodec>
+#ifdef Q_OS_WIN
+#include <windows.h>
+#endif
 
 TextStream::TextStream()
 {
@@ -57,14 +60,27 @@ TextStream::TextStream(const QByteArray& array, QIODevice::OpenMode openMode)
 
 void TextStream::detectCodec()
 {
-    QString codecName = "UTF-8";
+    QString codecName = QTextCodec::codecForLocale()->name();
+    if (codecName == "C") {
+        // Force UTF-8 on *nix systems with a C locale or else Unicode
+        // passwords will only be question marks.
+        codecName = "UTF-8";
+    }
     auto env = QProcessEnvironment::systemEnvironment();
+
 #ifdef Q_OS_WIN
-    if (!env.contains("SHELL")) {
-        // native shell (no Msys or cygwin)
+    codecName = "UTF-8";
+    WINBOOL success = false;
+#ifdef CP_UTF8
+    success = SetConsoleOutputCP(CP_UTF8);
+#endif
+    if (!success && !env.contains("SHELL")) {
+        // Fall back to cp850 if this is Windows without CP_UTF8 and we
+        // are running in a native shell (i.e., no Msys or Cygwin).
         codecName = "Windows-850";
     }
 #endif
+
     codecName = env.value("ENCODING_OVERRIDE", codecName);
     auto* codec = QTextCodec::codecForName(codecName.toLatin1());
     if (codec) {