How usable is Qt without its preprocessing step?

Question

I think it\'s unreasonable for a library to require preprocessing of my source code with a special tool. That said, several people have recommended the Qt library to me for cros

Answer 1

If you just need to connect to signals coming from Qt objects, a hack solution is to utilize existing QT objects that have public or protected virtual slots that match the signature of the signal you want to connect to. You can subclass the QT object and re-implement the virtual slot as a proxy to perform whatever action you need to when the QT signal is emitted. E.g.,

class SignalProxy : public QWidget
{
public:
  SignalProxy() {}

  void setVisible( bool isVisible )
  {
     // Do whatever you want to do when the signal is emitted.
  }
};


// code to connect the signal, e.g., to a QWebView object
SignalProxy proxy;
QWebView webview;
QObject::connect( &webview, SIGNAL(loadFinished(bool)),
        &proxy, SLOT(setVisible(bool)) );

It's not pretty but it gets the job done. If you were really intent on doing without the MOC you could probably locate existing Qt objects to use as proxies for just about any signal signature you need, e.g., the QAbstract... classes have lots of virtual slots, and you could hide all that nastiness in a library that provides a boost signals or tr1::function<> style API for connecting to QT signals.

Calling slots on QT objects is less of a concern than receiving signals, since you can generally invoke the slot method directly.