Overriding Qt Classes
We had a need to override the QSystemTrayIcon::showMessage() function on mac specifically across multiple projects. The trouble is ensuring that developers use the override function even if they don’t know about it. So:
namespace Moose
{
class QSystemTrayIcon : public ::QSystemTrayIcon
{
public:
void showMessage( const QString& title, const QString& text )
{
//code
}
};
}
#define QSystemTrayIcon Moose::QSystemTrayIcon
Name the file “QSystemTrayIcon” and save it in a directory like QtOverrides. Then add the following to your qmake project file:
CXX = $$CXX -IQtOverrides
Which forces our override directory to be earlier in the include path than the Qt includes.
This method scares me somewhat, due to the define, but I couldn’t see a neater way of doing it.
Now if a developer #includes <QSystemTrayIcon> they will be using our stealth reimplementation.
Of course this method isn’t virtual, but that shouldn’t be a problem, people don’t tend to use QWidgets in a way that requires polymorphism. Well that’s a lie, but most methods are safe, on final-type classes.