设计一个简单的游戏引擎

kirh_036

xp的好时代，来临力

kirh_036

控帧改为等待信号实现

写了个demo，验证windows下的WaitableTimer和STL sleep_for，结果令人很意外很失望。

源码：

1. #include <Windows.h>
   
2. #include <stdio.h>
   
3. #include <thread>
   
4. #include "SDL.h"
   
5. 
   
6. int main(int argc, char* argv[])
   
7. {
   
8.     uint64_t frequency = SDL_GetPerformanceFrequency();
   
9. #if 1
   
10.     HANDLE waitable_timer = CreateWaitableTimerW(
    
11.         nullptr,
    
12.         TRUE,
    
13.         nullptr);
    
14.     while (waitable_timer)
    
15.     {
    
16.         uint64_t before = SDL_GetPerformanceCounter();
    
17. 
    
18.         LARGE_INTEGER delay;
    
19.         delay.QuadPart = -1E7 / 60;
    
20.         SetWaitableTimer(
    
21.             waitable_timer,
    
22.             &delay,
    
23.             0, nullptr, nullptr, FALSE
    
24.         );
    
25.         WaitForSingleObject(waitable_timer, INFINITE);
    
26. 
    
27.         uint64_t after = SDL_GetPerformanceCounter();
    
28.         printf("call: %lld, real: %llu, error: %lld\n", -delay.QuadPart, after - before, llround(0.L + after - before + delay.QuadPart));
    
29.     }
    
30. #else
    
31.     while (true)
    
32.     {
    
33.         uint64_t before = SDL_GetPerformanceCounter();
    
34. 
    
35.         long long delay = 1E7 / 60;
    
36.         std::this_thread::sleep_for(std::chrono::nanoseconds(delay * 100));
    
37. 
    
38.         uint64_t after = SDL_GetPerformanceCounter();
    
39.         printf("call: %lld, real: %llu, error: %lld\n", delay, after - before, llround(0.L + after - before - delay));
    
40.     }
    
41. #endif
    
42.     return 0;
    
43. }

复制代码

运行结果：
WaitableTimer



STL sleep_for



结论：
WaitableTimer的精度实际上和STL sleep_for一样，都是15ms左右（具体数字取决于操作系统的调度时间片）的粒度。

P.S.：github不好发图，就借楼发了