Fixed #194: Scan Popup window doesn't get the keyboard focus on Linux.

Tested and verified on recent Unity, Gnome, KDE, LXDE systems.

scanpopup.cc

@@ -752,10 +752,28 @@ void ScanPopup::enterEvent( QEvent * event )
   }
 }
 
+void ScanPopup::requestWindowFocus()
+{
+  // One of the rare, actually working workarounds for requesting a user keyboard focus on X11,
+  // works for Qt::Popup windows, exactly like our Scan Popup (in unpinned state).
+  // Modern window managers actively resist to automatically focus pop-up windows.
+#ifdef Q_WS_X11
+  if ( !ui.pinButton->isChecked() )
+  {
+    QMenu m( this );
+    m.addAction( "" );
+    m.show();
+    m.hide();
+  }
+#endif
+}
+
 void ScanPopup::showEvent( QShowEvent * ev )
 {
   QMainWindow::showEvent( ev );
 
+  QTimer::singleShot(100, this, SLOT( requestWindowFocus() ) );
+  
   if ( groups.size() <= 1 ) // Only the default group? Hide then.
     ui.groupList->hide();
 

scanpopup.hh

@@ -71,6 +71,7 @@ signals:
 #endif
 
 public slots:
+  void requestWindowFocus();
 
   /// Translates the word from the clipboard, showing the window etc.
   void translateWordFromClipboard();