Day 18 done. FPS enforcing.

sdl_handmade.cpp

@@ -19,6 +19,14 @@
 
 global bool GlobalRunning;
 
+global U64 GlobalPerfCountFrequency;
+
+#define CONTROLLER_LEFT_THUMB_DEADZONE 8000
+#define MAX_CONTROLLERS 4
+SDL_GameController *ControllerHandles[MAX_CONTROLLERS];
+
+global offscreen_buffer GlobalBackbuffer;
+
 internal U32 SafeTruncateUInt64(U64 Value)
 {
 	Assert(Value <= 0xFFFFFFFF);
@@ -105,12 +113,6 @@ sdl_window_dimension SDLGetWindowDimension(SDL_Window *Window)
     return Dimension;
 }
 
-#define CONTROLLER_LEFT_THUMB_DEADZONE 8000
-#define MAX_CONTROLLERS 4
-SDL_GameController *ControllerHandles[MAX_CONTROLLERS];
-
-global offscreen_buffer GlobalBackbuffer;
-
 internal void SDLResizeTexture(offscreen_buffer *Buffer, SDL_Renderer *Renderer, int Width, int Height)
 {
     if(Buffer->Texture)
@@ -295,21 +297,30 @@ internal F32 SDLProcessInputStickValue(F32 Value, S32 DeadZoneThreshold)
     return Result;
 }
 
+#define DEFAULT_REFRESH_RATE 60
 internal S32 SDLGetWindowRefreshRate(SDL_Window *Window)
 {
-    SDL_DisplayMode Mode;
     int DisplayIndex = SDL_GetWindowDisplayIndex(Window);
-    // If we can't find the refresh rate, we'll return this:
-    int DefaultRefreshRate = 60;
+    SDL_DisplayMode Mode;
+
     if(SDL_GetDesktopDisplayMode(DisplayIndex, &Mode) != 0)
-        return DefaultRefreshRate;
+        return DEFAULT_REFRESH_RATE;
     if(Mode.refresh_rate == 0)
-        return DefaultRefreshRate;
+        return DEFAULT_REFRESH_RATE;
     return Mode.refresh_rate;
 }
 
+internal U64 SDLGetWallClock()
+{
+    return SDL_GetPerformanceCounter();
+}
 
-int main(int argc, char *argv[])
+internal F32 SDLGetSecondsElapsed(U64 Start, U64 End)
+{
+    return (F32)(End - Start) / (F32)GlobalPerfCountFrequency;
+}
+
+S32 main(int argc, char *argv[])
 {
     if(SDL_Init(SDL_INIT_VIDEO|SDL_INIT_GAMECONTROLLER|SDL_INIT_AUDIO)) {
         /* TODO: This didn't work . . . */
@@ -320,7 +331,8 @@ int main(int argc, char *argv[])
     SDL_Window *Window = SDL_CreateWindow("Handmade Hero", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 700, 500, SDL_WINDOW_RESIZABLE);
 
     if(Window) {
-        SDL_Renderer *Renderer = SDL_CreateRenderer(Window, -1, 0);
+        //SDL_Renderer *Renderer = SDL_CreateRenderer(Window, -1, 0);
+        SDL_Renderer *Renderer = SDL_CreateRenderer(Window, -1, SDL_RENDERER_PRESENTVSYNC);
         // "Wayland needs an event loop and rendering or it won't function." https://github.com/libsdl-org/SDL/issues/7699#issuecomment-1545684792
         // NOTE: This means that we need to readraw to even resize the window, otherwise the window frame will appear outdated to its actual size.
         // SDL_RenderPresent(Renderer) is enough to display the window.
@@ -368,18 +380,24 @@ int main(int argc, char *argv[])
                 game_input *OldInput = &Input[1];
                 memset(&Input, 0, sizeof(Input));
 
-                U64 PerfCountFrequency = SDL_GetPerformanceFrequency();
+                GlobalPerfCountFrequency = SDL_GetPerformanceFrequency();
+
                 U64 LastCounter;
 #if ARCH_X64 || ARCH_X86
                 U64 LastCycleCount;
 #endif
 
                 while(GlobalRunning) {
-                    LastCounter = SDL_GetPerformanceCounter();
+                    LastCounter = SDLGetWallClock();
+
 #if ARCH_X64 || ARCH_X86
                     LastCycleCount = __rdtsc(); // NOTE: rdtsc reports clock cylces, however it is not meant for really precise profiler work as the value returned is varied.
 #endif                                          // Also, __rdtsc is not available on MacOS ARM; I have not checked MacOS x64.
 
+                    S32 MonitorRefreshHz = SDLGetWindowRefreshRate(Window);
+                    S32 GameUpdateHz = MonitorRefreshHz;
+                    F32 TargetSecondsPerFrame = 1.0f / (F32)GameUpdateHz;
+
                     game_controller_input *OldKeyboardController = GetController(OldInput, 0);
                     game_controller_input *NewKeyboardController = GetController(NewInput, 0);
                     game_controller_input ZeroController = {0};
@@ -466,12 +484,28 @@ int main(int argc, char *argv[])
                     GameUpdateAndRender(&GameMemory, NewInput, &Buffer, &SoundBuffer);
                     SDLFillSoundBuffer(&SoundOutput, BytesToWrite);
 
+                    U64 WorkCounter = SDLGetWallClock();
+                    F32 WorkSecondsElapsed = SDLGetSecondsElapsed(LastCounter, WorkCounter);
+
+                    F32 SecondsElapsedForFrame = WorkSecondsElapsed;
+                    if(SecondsElapsedForFrame < TargetSecondsPerFrame) {
+                        while(SecondsElapsedForFrame < TargetSecondsPerFrame) {
+                            SecondsElapsedForFrame = SDLGetSecondsElapsed(LastCounter, SDLGetWallClock());
+                            SDL_Delay((U32)((TargetSecondsPerFrame - SecondsElapsedForFrame) * 1000.0f));
+                        }
+                    } else {
+                        // TODO: Missed frame rate!
+                        // TODO: Logging.
+                    }
+
+                    U64 EndCounter = SDLGetWallClock();
+
                     SDLDisplayBufferInWindow(GlobalBackbuffer, Window, Renderer);
 
-                    U64 EndCounter = SDL_GetPerformanceCounter();
-                    U64 CounterElapsed = EndCounter - LastCounter;
-                    F64 MSPerFrame = (((1000.0f * (F64)CounterElapsed) / (F64)PerfCountFrequency));
-                    F64 FPS = (F64)PerfCountFrequency / (F64)CounterElapsed;
+                    F64 MSPerFrame = 1000.0f * SDLGetSecondsElapsed(LastCounter, EndCounter);
+                    F64 FPS = 0.0f;
+
+                    LastCounter = EndCounter;
 
 #if ARCH_X64 || ARCH_X86
                     U64 EndCycleCount = __rdtsc();
@@ -482,7 +516,6 @@ int main(int argc, char *argv[])
 #else
                     fprintf(stderr, "%.02f ms/f, %.02f/s\n", MSPerFrame, FPS);
 #endif
-                    LastCounter = EndCounter;
 
                     Swap(game_input *, NewInput, OldInput);
                 }