update

.clangd

@@ -0,0 +1,5 @@
+CompileFlags:
+  Add: 
+    - -DHANDMADE_INTERNAL 
+    - -DHANDMADE_SLOW 
+    - -DHANDMADE_WIN32

misc/build.bat

@@ -14,7 +14,7 @@ cl ^
     -FC                                                             %= Full path of source code file in diagnostics =%^
     -Zi                                                             %= Generate debugger info =%^
     -Fe:handmade.exe ..\src\win32_handmade.cpp                      %= Output filename, input filename =%^
-    user32.lib Gdi32.lib                                            %= Linked libraries =%^
+    user32.lib Gdi32.lib winmm.lib                                  %= Linked libraries =%^
     /link -subsystem:windows,5.1                                    %= Linker stuff =%
 popd
 exit /b

src/handmade.h

@@ -26,7 +26,7 @@
  */
 
 #if HANDMADE_SLOW
-#define Assert(Expression) if (!(Expression)) {*(int *)0 = 0;}
+#define Assert(Expression) if (!(Expression)) {*(volatile int *)0 = 0;}
 #else
 #define Assert(Expression) 
 #endif

src/win32_handmade.cpp

@@ -3,6 +3,7 @@
 #include <Xinput.h>
 #include <dsound.h>
 
+// Local imports
 #include "win32_handmade.h"
 #include "handmade.cpp"
 
@@ -10,6 +11,7 @@ global ATOM HH_CTRLW;
 global bool globalRunning;
 global Win32OffscreenBuffer globalBackBuffer;
 global LPDIRECTSOUNDBUFFER globalSecondaryBuffer;
+global int64 globalPerfCountFrequency;
 
 // XInputGetState
 #define X_INPUT_GET_STATE(name) DWORD WINAPI name(DWORD dwUserIndex, XINPUT_STATE *pState)
@@ -91,6 +93,7 @@ internal void resizeDIBSection(Win32OffscreenBuffer *buffer, int width, int heig
 
     buffer->width = width;
     buffer->height = height;
+    buffer->bytesPerPixel = 4;
 
     buffer->info.bmiHeader.biSize = sizeof(buffer->info.bmiHeader);
     buffer->info.bmiHeader.biWidth = buffer->width;
@@ -351,10 +354,62 @@ internal void win32ProcessPendingMessages(GameControllerInput *keyboardControlle
     }
 }
 
+inline LARGE_INTEGER win32GetWallClock() {
+    LARGE_INTEGER result;
+    QueryPerformanceCounter(&result);
+    return result;
+}
+
+inline real32 win32GetSecondsElapsed(LARGE_INTEGER start, LARGE_INTEGER end) {
+    return (real32)(end.QuadPart - start.QuadPart) / (real32)globalPerfCountFrequency;
+}
+
+//    int monitorRefreshHz = 60;
+//    int gameUpdateHz = monitorRefreshHz / 2;
+
+#define framesOfAudioLatency 3
+#define monitorRefreshHz 60
+#define gameUpdateHz (monitorRefreshHz / 2)
+
+internal void win32DebugDrawVertical(Win32OffscreenBuffer *screenBuffer, int x, int top, int bottom, int32 color) {
+    int pitch = screenBuffer->width*screenBuffer->bytesPerPixel; 
+    uint8 *pixel = (uint8 *)screenBuffer->memory + top * pitch + x*screenBuffer->bytesPerPixel;
+    for (int y = top; y < bottom; y++) {
+        *(uint32 *)pixel = color;
+        pixel += pitch;
+    }
+}
+
+inline void win32DrawSoundBufferMarker(Win32OffscreenBuffer *buffer, Win32SoundOutput *soundOutput, real32 pxPerSoundBufferEntry, int padX, int top, int bottom, DWORD value, uint32 color) {
+    Assert(value < (DWORD)soundOutput->secondaryBufferSize);
+    int x = padX + (int)(pxPerSoundBufferEntry * (real32)value);
+    win32DebugDrawVertical(buffer, x, top, bottom, color);
+}
+
+internal void win32DebugSyncDisplay(Win32OffscreenBuffer *screenBuffer, int markerCount, Win32DebugTimeMarker *markers, Win32SoundOutput *soundOutput, real32 targetSecondsPerFrame) {
+    int padX = 16;
+    int padY = 16;
+
+    int top = padY;
+    int bottom = screenBuffer->height - padY;
+    int renderWidth = screenBuffer->width - 2 *padX;
+
+    real32 pxPerSoundBufferEntry = (real32)renderWidth / (real32)soundOutput->secondaryBufferSize;
+
+    for (int markerIndex = 0; markerIndex < markerCount; markerIndex++) {
+        Win32DebugTimeMarker *thisMarker = &markers[markerIndex];
+        win32DrawSoundBufferMarker(screenBuffer, soundOutput, pxPerSoundBufferEntry, padX, top, bottom, thisMarker->playCursor, 0xFFFFFFFF);
+        win32DrawSoundBufferMarker(screenBuffer, soundOutput, pxPerSoundBufferEntry, padX, top, bottom, thisMarker->writeCursor, 0xFFFF0000);
+    }
+}
+
 int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLine, int commandShow) {
     LARGE_INTEGER performanceFrequencyResult;
     QueryPerformanceFrequency(&performanceFrequencyResult);
-    int64 performanceFrequency = performanceFrequencyResult.QuadPart;
+    globalPerfCountFrequency = performanceFrequencyResult.QuadPart;
+
+    UINT desiredSchedulerMs = 1;
+    bool32 sleepIsGranular = TIMERR_NOERROR == timeBeginPeriod(desiredSchedulerMs);
 
     WNDCLASSA windowClass = {};
     windowClass.style = CS_VREDRAW | CS_HREDRAW;
@@ -364,6 +419,8 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
 
     resizeDIBSection(&globalBackBuffer, 1280, 720);
 
+    real32 targetSecondsPerFrame = 1.0f / (real32)gameUpdateHz;
+
     if (RegisterClass(&windowClass)) {
         HWND window = CreateWindowExA(
             NULL,
@@ -388,6 +445,9 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
             GameInput *oldInput = &input[0];
             GameInput *newInput = &input[1];
 
+            int debugTimeMarkerIndex = 0; 
+            Win32DebugTimeMarker debugMarkers[gameUpdateHz / 2] = {};
+
             win32LoadXInput();
 
             // sound test
@@ -396,7 +456,7 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
             soundOutput.runningSampleIndex = 0;
             soundOutput.bytesPerSample = sizeof(int16)*2;
             soundOutput.secondaryBufferSize = soundOutput.samplesPerSecond*soundOutput.bytesPerSample;
-            soundOutput.latencySampleCount = (int)(soundOutput.samplesPerSecond / 15.0f);
+            soundOutput.latencySampleCount = framesOfAudioLatency * (soundOutput.samplesPerSecond / gameUpdateHz);
 
             int16 *samples = (int16*)VirtualAlloc(NULL, soundOutput.secondaryBufferSize, MEM_COMMIT, PAGE_READWRITE);
 
@@ -417,9 +477,13 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
             win32ClearBuffer(&soundOutput);
             globalSecondaryBuffer->Play(0, 0, DSBPLAY_LOOPING);
 
-            LARGE_INTEGER lastCounter;
-            QueryPerformanceCounter(&lastCounter);
+            LARGE_INTEGER lastWorkCounter = win32GetWallClock();
+
             int64 lastCycleCount = __rdtsc();
+
+            bool32 soundIsValid = false;
+            DWORD lastPlayCursor = 0;
+
             while (globalRunning) {
                 GameControllerInput *oldKeyboardController = &oldInput->controllers[0];
                 GameControllerInput *newKeyboardController = &newInput->controllers[0];
@@ -499,15 +563,12 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
                 videoBuffer.height = globalBackBuffer.height;
 
                 // Sound test
-                DWORD playCursor = 0;
-                DWORD writeCursor = 0;
                 DWORD byteToLock = 0;
-                DWORD targetCursor = 0;
+                DWORD targetCursor = lastPlayCursor;
                 DWORD bytesToWrite = 0;
-                bool soundIsValid = true;
-                if (SUCCEEDED(globalSecondaryBuffer->GetCurrentPosition(&playCursor, &writeCursor))) {
+                if (soundIsValid) {
                     byteToLock = (soundOutput.runningSampleIndex*soundOutput.bytesPerSample) % soundOutput.secondaryBufferSize;
-                    targetCursor = (playCursor + soundOutput.latencySampleCount*soundOutput.bytesPerSample) % soundOutput.secondaryBufferSize;
+                    targetCursor = (lastPlayCursor + soundOutput.latencySampleCount*soundOutput.bytesPerSample) % soundOutput.secondaryBufferSize;
                     if (byteToLock == targetCursor) {
                         bytesToWrite = 0;
                     } else if (byteToLock > targetCursor) {
@@ -515,7 +576,6 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
                     } else {
                         bytesToWrite = targetCursor - byteToLock;
                     }
-                    soundIsValid = true;
                 }
 
                 GameSoundOutputBuffer soundBuffer = {};
@@ -524,23 +584,66 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
                 soundBuffer.samples = samples;
 
                 gameUpdateAndRender(&gameMemory, &videoBuffer, newInput, &soundBuffer);
-
                 if (soundIsValid) {
                     win32FillSoundBuffer(&soundOutput, byteToLock, bytesToWrite, &soundBuffer);
                 }
+
+                real32 secondsElapsedForFrame = win32GetSecondsElapsed(lastWorkCounter, win32GetWallClock());
+                if (secondsElapsedForFrame < targetSecondsPerFrame) {
+                    if (sleepIsGranular) {
+                        DWORD sleepMs = (DWORD)(1000.0f * (targetSecondsPerFrame - secondsElapsedForFrame));
+                        if (sleepMs > 0) {
+                            Sleep(sleepMs);
+                        }
+                    }
+                    while (secondsElapsedForFrame < targetSecondsPerFrame) {
+                        secondsElapsedForFrame = win32GetSecondsElapsed(lastWorkCounter, win32GetWallClock());
+                    }
+                } else {
+                    // logging, MISSED FRAME!
+                }
+
+                lastWorkCounter = win32GetWallClock();
+
+#if HANDMADE_INTERNAL
+                win32DebugSyncDisplay(&globalBackBuffer, ArrayCount(debugMarkers), debugMarkers, &soundOutput, targetSecondsPerFrame);
+#endif
+
                 win32DrawBufferInWindow(&globalBackBuffer, window);
 
-                LARGE_INTEGER endCounter;
-                QueryPerformanceCounter(&endCounter);
+                DWORD playCursor = 0;
+                DWORD writeCursor = 0;
+                if (SUCCEEDED(globalSecondaryBuffer->GetCurrentPosition(&playCursor, &writeCursor))) {
+                    lastPlayCursor = playCursor;
+                    if (!soundIsValid) {
+                        soundOutput.runningSampleIndex = writeCursor / soundOutput.bytesPerSample;
+                        soundIsValid = true;
+                    }
+                } else {
+                    soundIsValid = false;
+                }
+
+#if HANDMADE_INTERNAL
+                {
+                    Assert(debugTimeMarkerIndex < ArrayCount(debugMarkers));
+
+                    Win32DebugTimeMarker *marker = &debugMarkers[debugTimeMarkerIndex++];
+
+                    if (debugTimeMarkerIndex >= ArrayCount(debugMarkers)) {
+                        debugTimeMarkerIndex = 0;
+                    }
+                    
+                    globalSecondaryBuffer->GetCurrentPosition(&marker->playCursor, &marker->writeCursor);
+                }
+#endif
+
+#if 0
+                real64 msElapsed = (real32)(1000.0f*secondsElapsedForFrame) / globalPerfCountFrequency;
+                real64 fps = (real32)(1000.0f*globalPerfCountFrequency/(real32)secondsElapsedForFrame)/1000.0f;
                 int64 endCycleCount = __rdtsc();
                 int64 cyclesElapsed = endCycleCount - lastCycleCount;
                 lastCycleCount = endCycleCount;
-
-                int64 counterElapsed = endCounter.QuadPart - lastCounter.QuadPart;
-                real32 msElapsed = (real32)(1000.0f*counterElapsed) / performanceFrequency;
-                real32 fps = (real32)(1000.0f*performanceFrequency/(real32)counterElapsed)/1000.0f;
-
-                lastCounter = endCounter;
+#endif
 
                 GameInput *temp = newInput;
                 newInput = oldInput; 
@@ -552,6 +655,7 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
     } else {
         // failed
     }
-    return(0);
+
+    return 0;
 }
 

src/win32_handmade.h

@@ -22,3 +22,8 @@ struct Win32SoundOutput {
     real32 tSine;
     int latencySampleCount;
 };
+
+struct Win32DebugTimeMarker {
+    DWORD playCursor;
+    DWORD writeCursor;
+};