
Originally Posted by
TheBlackCat
Because that is the whole point of using a declarative language. With an imperative language like C++, you have to tell the system exactly how to do what you want it to do. With a declarative language you tell the system what you want in the end, and the system figures out the best way to accomplish it. And the latter case is exactly what scenegraph is all about, it knows what the finished product should look like, so it can then figure out exactly how to go about producing that in the most efficient possible way. That is fundamentally impossible with an imperative language like C++, where you have to manually lay out each rendering step.
I guess, theoretically, you could embed a new declarative language inside C++ code, but that really doesn't do what you want it to do, because it still wouldn't be C++, in the end it would still be a new language.
And you can't do it at all with qwidget, since by definition qwidgets have their rendering code inside the class, which is exactly what scenegraph was designed to avoid. So no matter how you implemented the declarative language, you could never use qwidget.