DirectSound: Drain the playback buffer when stopping the device.

mini_al.h

@@ -9631,9 +9631,44 @@ mal_result mal_device_main_loop__dsound(mal_device* pDevice)
 
     /* Getting here means the device is being stopped. */
 
-    /* The playback device should be drained before stopping. */
+    /* The playback device should be drained before stopping. All we do is wait until the available bytes is equal to the size of the buffer. */
     if (isPlaybackDeviceStarted) {
-        /* TODO: Drain the playback device. */
+        for (;;) {
+            DWORD availableBytesPlayback = 0;
+            DWORD physicalPlayCursorInBytes;
+            DWORD physicalWriteCursorInBytes;
+            if (FAILED(mal_IDirectSoundBuffer_GetCurrentPosition((mal_IDirectSoundBuffer*)pDevice->dsound.pPlaybackBuffer, &physicalPlayCursorInBytes, &physicalWriteCursorInBytes))) {
+                break;
+            }
+
+            if (physicalPlayCursorInBytes < prevPlayCursorInBytesPlayback) {
+                physicalPlayCursorLoopFlagPlayback = !physicalPlayCursorLoopFlagPlayback;
+            }
+            prevPlayCursorInBytesPlayback  = physicalPlayCursorInBytes;
+
+            if (physicalPlayCursorLoopFlagPlayback == virtualWriteCursorLoopFlagPlayback) {
+                /* Same loop iteration. The available bytes wraps all the way around from the virtual write cursor to the physical play cursor. */
+                if (physicalPlayCursorInBytes <= virtualWriteCursorInBytesPlayback) {
+                    availableBytesPlayback  = (pDevice->playback.internalBufferSizeInFrames*bpfPlayback) - virtualWriteCursorInBytesPlayback;
+                    availableBytesPlayback += physicalPlayCursorInBytes;    /* Wrap around. */
+                } else {
+                    break;
+                }
+            } else {
+                /* Different loop iterations. The available bytes only goes from the virtual write cursor to the physical play cursor. */
+                if (physicalPlayCursorInBytes >= virtualWriteCursorInBytesPlayback) {
+                    availableBytesPlayback = physicalPlayCursorInBytes - virtualWriteCursorInBytesPlayback;
+                } else {
+                    break;
+                }
+            }
+
+            if (availableBytesPlayback >= (pDevice->playback.internalBufferSizeInFrames*bpfPlayback)) {
+                break;
+            }
+
+            mal_sleep(waitTimeInMilliseconds);
+        }
     }
 
     if (pDevice->type == mal_device_type_capture || pDevice->type == mal_device_type_duplex) {