RenderWindow::create((sf::WindowHandle) winId());
In my case it worked fine. If you want to use Qt&SFML without implementing everything on your own you can use my library – QSFML. https://github.com/KoczurekK/QSFML (https://github.com/KoczurekK/QSFML)
long long unsigned int is implicitly convertible to long unsigned int (aka unsigned long), it may only show a warning due to potential type narrowing. So unless you want to remove the warning a cast is not needed and when you do use a cast, static_cast should be used.
This test code works fine on Ideone (https://ideone.com/scOwPR).
#include <iostream>
int main() {
unsigned long ul = 10;
long long unsigned int llui = 20;
std::cout << ul << " " << llui << "\n";
ul = llui;
ul = static_cast<long unsigned int>(llui);
std::cout << ul << " " << llui << "\n";
}
My guess is that because there was an issue ("hanging"?) when using an implicit cast or a static_cast, you assumed that this must be the origin of the issue, while it actually might be somewhere else entirely (see also XY Problem (http://xyproblem.info/)). ;)
So what exactly is your problem with an implicit cast?