Although class dcpp::shared_device is very similar with std::shared_ptr, and it borrows the idea from std::shared_ptr, but it is not std::shared_ptr. dcpp::shared_device is used to manage underlying device pointer, but it is not used for pointer, it is used for object (std::shared_ptr object is object too).

The std::shared_ptr object can be used as bool checker:

if (object)
	...

And dcpp::shared_device needs to do similar things.

However, dcpp::shared_device is very different from std::shared_ptr. The device validation check is complicated. Checking underlying device is not just like checking a c++ integral value.

To distinguish clearly, operator bool won't be provided.

Instead, an explicit method .has_device() is provided.

c++ example

#include <duckcpp/shared.hpp>
#include <iostream>

namespace my_space
{

class my_application
{
private:
	dcpp::shared_device __device;
public:
	my_application(dcpp::shared_device device__):
		__device{device__}
	{
		// Before leaving constructor, the use count is 3.
	}
public:
	void run()
	{
		if (! __device.has_device())
		{
			throw std::runtime_error{"ERROR: sorry, no device"};
		}
		while (__device.run())
		{
			if (! __device.window_active())
			{
				__device.yield();
				continue;
			}
			__device.scene()->drawAll();
			__device.video()->swapScenes(0xff123456);
		}
	}
	dcpp::int32_kt use_count()
	{
		return __device.use_count();
	}
};

}

int main()
try
{
	dcpp::shared_device device{2560, 1440};
	my_space::my_application app{device};
	std::cout << "Use count: " << device.use_count() << std::endl;	// 2
	std::cout << "Use count: " << app.use_count() << std::endl;	// 2
	if (false)
	{
		device.destroy();
		std::cout << "Use count: " << device.use_count() << std::endl;	// 0
		std::cout << "Use count: " << app.use_count() << std::endl;	// 0
	}
	// If above block is executed, the following run will throw exception.
	app.run();
	return 0;
}
catch (const std::exception & e)
{
	std::cout << e.what() << std::endl;
	return 0;
}

Date

> date
Mon Apr  7 09:22:06 AM UTC 2025

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