diff --git a/examples/termcap.cpp b/examples/termcap.cpp
index 4f729329..09b5cb07 100644
--- a/examples/termcap.cpp
+++ b/examples/termcap.cpp
@@ -205,12 +205,16 @@ void tcapString (const std::string& name, const char cap_str[])
 //----------------------------------------------------------------------
 void debug (FApplication& TermApp)
 {
+  const FString& ab_s = TermApp.getAnswerbackString();
+  const FString& sec_da= TermApp.getSecDAString();
+
 #if DEBUG
   std::cout << "\n.------------------- debug -------------------\r\n";
 #if defined(__linux__)
   std::cout << "|               Framebuffer bpp: "
             << TermApp.framebuffer_bpp << "\r\n";
 #endif
+
   std::cout << "| after init_256colorTerminal(): "
             << TermApp.termtype_256color << "\r\n";
   std::cout << "|    after parseAnswerbackMsg(): "
@@ -218,11 +222,11 @@ void debug (FApplication& TermApp)
   std::cout << "|            after parseSecDA(): "
             << TermApp.termtype_SecDA << "\r\n";
 
-  if ( const FString& s = TermApp.getAnswerbackString() )
-    tcapString ("|         The answerback String", s);
+  if ( ab_s.isEmpty() )
+    tcapString ("|         The answerback String", ab_s);
 
-  if (  const FString& s = TermApp.getSecDAString() )
-    tcapString ("|              The SecDA String", s);
+  if ( ab_s.isEmpty() )
+    tcapString ("|              The SecDA String", sec_da);
 
   std::cout << "`------------------- debug -------------------\r\n";
 #endif
diff --git a/examples/ui.cpp b/examples/ui.cpp
index 52c0ba39..c2c94615 100644
--- a/examples/ui.cpp
+++ b/examples/ui.cpp
@@ -1018,7 +1018,7 @@ void MyDialog::cb_view (FWidget*, data_ptr data)
   FString file;
   FMenuItem* item = static_cast<FMenuItem*>(data);
 
-  if ( item && item->getText() )
+  if ( item && ! item->getText().isEmpty() )
     file = item->getText();
   else
     file = FFileDialog::fileOpenChooser (this);
diff --git a/include/final/fstring.h b/include/final/fstring.h
index f656dac2..cded68c5 100644
--- a/include/final/fstring.h
+++ b/include/final/fstring.h
@@ -226,6 +226,7 @@ class FString
     wchar_t  front() const;
     wchar_t  back()  const;
 
+    FString& sprintf (const FString&, ...);
     FString& sprintf (const wchar_t[], ...);
     FString& sprintf (const char[], ...)
 #if defined(__clang__)
diff --git a/src/fbutton.cpp b/src/fbutton.cpp
index 1d30a7b5..9232a553 100644
--- a/src/fbutton.cpp
+++ b/src/fbutton.cpp
@@ -250,10 +250,10 @@ bool FButton::setDown (bool on)
 //----------------------------------------------------------------------
 void FButton::setText (const FString& txt)
 {
-  if ( txt )
-    text = txt;
-  else
+  if ( txt.isNull() )
     text = "";
+  else
+    text = txt;
 
   detectHotkey();
 }
diff --git a/src/fdialog.cpp b/src/fdialog.cpp
index 5461afbe..7c753528 100644
--- a/src/fdialog.cpp
+++ b/src/fdialog.cpp
@@ -1212,7 +1212,7 @@ void FDialog::drawTextBar()
     print (' ');
 
   // Print title bar text
-  if ( tb_text )
+  if ( ! tb_text.isEmpty() )
   {
     if ( length <= getWidth() - MENU_BTN - zoom_btn )
       print (tb_text);
diff --git a/src/ffiledialog.cpp b/src/ffiledialog.cpp
index d97a7d6c..ecb3af74 100644
--- a/src/ffiledialog.cpp
+++ b/src/ffiledialog.cpp
@@ -108,7 +108,7 @@ FFileDialog::FFileDialog ( const FString& dirname
   , dlg_type(type)
   , show_hidden(false)
 {
-  if ( dirname )
+  if ( ! dirname.isNull() )
     setPath(dirname);
 
   init();
diff --git a/src/fmouse.cpp b/src/fmouse.cpp
index adfa720d..f263808f 100644
--- a/src/fmouse.cpp
+++ b/src/fmouse.cpp
@@ -371,11 +371,10 @@ bool FMouseGPM::gpmMouse (bool on)
 
     switch ( gpm_fd )
     {
-      case -1:
+      case -1:  // error
         return false;
 
-      case -2:
-        Gpm_Close();
+      case -2:  // xterm is in use
         return false;
 
       default:
@@ -503,11 +502,11 @@ void FMouseX11::setRawData (char fifo_buf[], int fifo_buf_size)
   for (n = len; n < fifo_buf_size; n++)
     fifo_buf[n - len] = fifo_buf[n];
 
-  n = fifo_buf_size - len - 1;
+  n = fifo_buf_size - len;
 
   // Fill rest with '\0'
   for (; n < fifo_buf_size; n++)
-    fifo_buf[n - len] = '\0';
+    fifo_buf[n] = '\0';
 
   input_data_pending = bool(fifo_buf[0] != '\0');
 }
@@ -1238,8 +1237,6 @@ void FMouseControl::clearEvent()
 #ifdef F_HAVE_LIBGPM
 void FMouseControl::setStdinNo (int file_descriptor)
 {
-
-
   FMouse* mouse = mouse_protocol[FMouse::gpm];
   FMouseGPM* gpm_mouse = static_cast<FMouseGPM*>(mouse);
 
diff --git a/src/fstring.cpp b/src/fstring.cpp
index 5a4882c5..a4883aa5 100644
--- a/src/fstring.cpp
+++ b/src/fstring.cpp
@@ -734,6 +734,27 @@ uInt FString::getUTF8length() const
   return len;
 }
 
+//----------------------------------------------------------------------
+FString& FString::sprintf (const FString& format, ...)
+{
+  static const int BUFSIZE = 4096;
+  wchar_t buffer[BUFSIZE];
+  va_list args;
+
+  if ( ! format )
+  {
+    clear();
+    return *this;
+  }
+
+  va_start (args, format);
+  std::vswprintf (buffer, BUFSIZE, format.wc_str(), args);
+  va_end (args);
+
+  _assign (buffer);
+  return *this;
+}
+
 //----------------------------------------------------------------------
 FString& FString::sprintf (const wchar_t format[], ...)
 {
@@ -741,6 +762,12 @@ FString& FString::sprintf (const wchar_t format[], ...)
   wchar_t buffer[BUFSIZE];
   va_list args;
 
+  if ( ! format )
+  {
+    clear();
+    return *this;
+  }
+
   va_start (args, format);
   std::vswprintf (buffer, BUFSIZE, format, args);
   va_end (args);
@@ -758,6 +785,12 @@ FString& FString::sprintf (const char format[], ...)
   int   len;
   va_list args;
 
+  if ( ! format )
+  {
+    clear();
+    return *this;
+  }
+
   buffer = buf;
   va_start (args, format);
   len = vsnprintf (buffer, sizeof(buf), format, args);
diff --git a/src/test/fmouse-test.cpp b/src/test/fmouse-test.cpp
index 194da783..0a63f0d2 100644
--- a/src/test/fmouse-test.cpp
+++ b/src/test/fmouse-test.cpp
@@ -96,7 +96,10 @@ class FMouseTest : public CPPUNIT_NS::TestFixture
     void noArgumentTest();
     void doubleClickTest();
     void workspaceSizeTest();
-
+#ifdef F_HAVE_LIBGPM
+    void gpmMouseTest();
+#endif
+    void x11MouseTest();
 
   private:
     // Adds code needed to register the test suite
@@ -107,6 +110,10 @@ class FMouseTest : public CPPUNIT_NS::TestFixture
     CPPUNIT_TEST (noArgumentTest);
     CPPUNIT_TEST (doubleClickTest);
     CPPUNIT_TEST (workspaceSizeTest);
+#ifdef F_HAVE_LIBGPM
+    CPPUNIT_TEST (gpmMouseTest);
+#endif
+    CPPUNIT_TEST (x11MouseTest);
 
     // End of test suite definition
     CPPUNIT_TEST_SUITE_END();
@@ -221,6 +228,63 @@ void FMouseTest::workspaceSizeTest()
   CPPUNIT_ASSERT ( mouse.getMaxHeight() == 30 );
 }
 
+#ifdef F_HAVE_LIBGPM
+//----------------------------------------------------------------------
+void FMouseTest::gpmMouseTest()
+{
+  FMouseGPM gpm_mouse;
+  CPPUNIT_ASSERT ( ! gpm_mouse.isGpmMouseEnabled() );
+
+  gpm_mouse.setStdinNo(fileno(stdin));
+
+  if ( gpm_mouse.enableGpmMouse() )
+  {
+    CPPUNIT_ASSERT ( gpm_mouse.isGpmMouseEnabled() );
+    timeval tv;
+    FObject::getCurrentTime(&tv);
+    gpm_mouse.processEvent(&tv);
+    CPPUNIT_ASSERT ( ! gpm_mouse.hasEvent() );
+  }
+  else
+    CPPUNIT_ASSERT ( ! gpm_mouse.isGpmMouseEnabled() );
+
+  gpm_mouse.disableGpmMouse();
+  CPPUNIT_ASSERT ( ! gpm_mouse.isGpmMouseEnabled() );
+}
+#endif
+
+//----------------------------------------------------------------------
+void FMouseTest::x11MouseTest()
+{
+  FMouseX11 x11_mouse;
+  CPPUNIT_ASSERT ( ! x11_mouse.hasData() );
+
+  char x11_mouse_data[8] = { 0x1b, '[', 'M', 0x23, 0x50, 0x32, 0x40, 0x40 };
+  x11_mouse.setRawData (x11_mouse_data, 8);
+  CPPUNIT_ASSERT ( x11_mouse.hasData() );
+  CPPUNIT_ASSERT ( x11_mouse.isInputDataPending() );
+
+  timeval tv;
+  FObject::getCurrentTime(&tv);
+  x11_mouse.processEvent (&tv);
+
+  CPPUNIT_ASSERT ( x11_mouse.getPos() == FPoint(48, 18) );
+  CPPUNIT_ASSERT ( x11_mouse.hasEvent() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isLeftButtonPressed() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isLeftButtonReleased() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isLeftButtonDoubleClick() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isRightButtonPressed() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isRightButtonReleased() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isMiddleButtonPressed() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isMiddleButtonReleased() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isShiftKeyPressed() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isControlKeyPressed() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isMetaKeyPressed() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isWheelUp() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isWheelDown() );
+  CPPUNIT_ASSERT ( ! x11_mouse.isMoved() );
+}
+
 
 // Put the test suite in the registry
 CPPUNIT_TEST_SUITE_REGISTRATION (FMouseTest);