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#pragma once
#include <QObject>
#include <thread>
#include <condition_variable>
#include <utility>
namespace qt_impl_detail {
template<typename t>
struct run_in_thread_traits
{
using type = t;
using ret_type = t&&;
static inline void assign(t& lvalue, t&& rvalue) { lvalue = rvalue; }
static inline ret_type&& pass(ret_type&& val) { return std::move(val); }
template<typename F> static ret_type call(F& fun) { return std::move(fun()); }
};
template<>
struct run_in_thread_traits<void>
{
using type = unsigned char;
using ret_type = void;
static inline void assign(unsigned char&, unsigned char&&) {}
static inline void pass(type&&) {}
template<typename F> static type call(F& fun) { fun(); return type(0); }
};
}
template<typename F>
auto run_in_thread_sync(QObject* obj, F&& fun)
-> typename qt_impl_detail::run_in_thread_traits<decltype(std::forward<F>(fun)())>::ret_type
{
using lock_guard = std::unique_lock<std::mutex>;
std::mutex mtx;
lock_guard guard(mtx);
std::condition_variable cvar;
std::thread::id waiting_thread = std::this_thread::get_id();
using traits = qt_impl_detail::run_in_thread_traits<decltype(std::forward<F>(fun)())>;
typename traits::type ret;
bool skip_wait = false;
{
QObject src;
src.moveToThread(obj->thread());
QObject::connect(&src,
&QObject::destroyed,
obj,
[&]() {
std::thread::id calling_thread = std::this_thread::get_id();
if (waiting_thread == calling_thread)
{
skip_wait = true;
traits::assign(ret, traits::call(fun));
}
else
{
lock_guard guard(mtx);
traits::assign(ret, traits::call(fun));
cvar.notify_one();
}
},
Qt::AutoConnection);
}
if (!skip_wait)
cvar.wait(guard);
return traits::pass(std::move(ret));
}
template<typename F>
void run_in_thread_async(QObject* obj, F&& fun)
{
QObject src;
src.moveToThread(obj->thread());
QObject::connect(&src, &QObject::destroyed, obj, std::move(fun), Qt::AutoConnection);
}
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