Better framepacing - Windows SDL Edition (#330)

* Use high-resolution timer on Win 10

* Better timing for windows

Couldn't figure out that stuff for other compilers, OSes and architectures. sorry

src/graphic/Fast3D/gfx_sdl2.cpp

@@ -42,6 +42,7 @@
 #include "gfx_screen_config.h"
 #ifdef _WIN32
 #include <WTypesbase.h>
+#include <Windows.h>
 #endif
 
 #define GFX_BACKEND_NAME "SDL"
@@ -318,7 +319,12 @@ static void gfx_sdl_init(const char* game_name, const char* gfx_api_name, bool s
 #endif
 
 #ifdef _WIN32
-    timer = CreateWaitableTimer(nullptr, false, nullptr);
+    // Use high-resolution timer by default on Windows 10 (so that NtSetTimerResolution (...) hacks are not needed)
+    timer = CreateWaitableTimerExW(nullptr, nullptr, CREATE_WAITABLE_TIMER_HIGH_RESOLUTION, TIMER_ALL_ACCESS);
+    // Fallback to low resolution timer if unsupported by the OS
+    if (timer == nullptr) {
+        timer = CreateWaitableTimer(nullptr, false, nullptr);
+    }
 #endif
 
     char title[512];
@@ -535,7 +541,11 @@ static inline void sync_framerate_with_timer(void) {
     t = qpc_to_100ns(SDL_GetPerformanceCounter());
 
     const int64_t next = previous_time + 10 * FRAME_INTERVAL_US_NUMERATOR / FRAME_INTERVAL_US_DENOMINATOR;
-    const int64_t left = next - t;
+    int64_t left = next - t;
+#ifdef _WIN32
+    // We want to exit a bit early, so we can busy-wait the rest to never miss the deadline
+    left -= 15000UL;
+#endif
     if (left > 0) {
 #ifndef _WIN32
         const timespec spec = { 0, left * 100 };
@@ -549,6 +559,12 @@ static inline void sync_framerate_with_timer(void) {
 #endif
     }
 
+#ifdef _WIN32
+    do {
+        YieldProcessor(); // TODO: Find a way for other compilers, OSes and architectures
+        t = qpc_to_100ns(SDL_GetPerformanceCounter());
+    } while (t < next);
+#endif
     t = qpc_to_100ns(SDL_GetPerformanceCounter());
     if (left > 0 && t - next < 10000) {
         // In case it takes some time for the application to wake up after sleep,