Hi!
Tavmjonh Bah has suggested me to contact you and consult SPPaintServer class refactoring I would like to do.
Currently SPPaintServer contains pattern_new method. Since it directly handles rendering and uses cairo, I think it could be moved outside of SP tree.
My idea is to implement paint server drawing routines in a parallel hierarchy of classes belonging to New Renderer. Image [1] contains the class diagram. Common base for them would be NRPaintServer, containing pure virtual method pattern_new. Concrete NRPaintServer derivatives would contain a reference to corresponding SPTree items and use it while rendering.
To choose an appropriate NRPaintServer for given SPPaintServer I thought about a factory method in NRPaintServer class. Example interfaces and their usage are shown at [2]
The tricky part can be the implementation of NRPaintServer::create method. I have thought about two solutions:
a) using a battery of dynamic_cast if statements like this:
NRPaintServer* NRPaintServer::create(SPPaintServer* ps) {
SPPattern* pattern = dynamic_cast<SPPattern*>ps;
if (pattern != 0) {
return new NRPattern(&pattern);
}
//and so on for gradients
}
b) using double-dispatch strategy. There would be an .cpp file internal class NRPaintServerFactory.
class NRPaintServerFactory {
public:
virtual NRPaintServer* create(SPPaintServer*);
virtual NRPaintServer* create(SPLinearGradient*);
virtual NRPaintServer* create(SPRadialGradient*);
//and so on
}
And NRPaintServer::create implementation would look like this:
NRPaintServer* NRPaintServer::create(SPPaintServer* ps) {
static NRPaintServerFactory *factory = new NRPaintServerFactory;
return factory->create(ps);
}
What are your thoughts about this solution?
Regards,
Tomasz
