Fix (or at least work around) missing messages problem

build/staging/version/BundleInfo.wxi

@@ -1,4 +1,4 @@
 <Include>
   <?define SetupVersionName="Developer Preview 4" ?>
-  <?define SetupVersionNumber="1.0.24018.1804" ?>
+  <?define SetupVersionNumber="1.0.24018.1827" ?>
 </Include>

src/api/Libs/MidiXProc/MidiXProc.cpp

@@ -271,74 +271,76 @@ CMidiXProc::SendMidiMessage(
     PMEMORY_MAPPED_DATA Data = &(m_MidiOut->Data);
 
     do{
-        try
+        // the write position is the last position we have written,
+        // the read position is the last position the driver has read from
+        ULONG writePosition = InterlockedCompareExchange((LONG*)Registers->WritePosition, 0, 0);
+        ULONG readPosition = InterlockedCompareExchange((LONG*)Registers->ReadPosition, 0, 0);
+        ULONG newWritePosition = (writePosition + requiredBufferSize) % Data->BufferSize;
+        ULONG bytesAvailable{ 0 };
+
+        // Calculate the available space in the buffer.
+        if (readPosition <= writePosition)
         {
-            // the write position is the last position we have written,
-            // the read position is the last position the driver has read from
-            ULONG writePosition = InterlockedCompareExchange((LONG*)Registers->WritePosition, 0, 0);
-            ULONG readPosition = InterlockedCompareExchange((LONG*)Registers->ReadPosition, 0, 0);
-            ULONG newWritePosition = (writePosition + requiredBufferSize) % Data->BufferSize;
-            ULONG bytesAvailable{ 0 };
-
-            // Calculate the available space in the buffer.
-            if (readPosition <= writePosition)
+            bytesAvailable = Data->BufferSize - (writePosition - readPosition);
+        }
+        else
+        {
+            bytesAvailable = (readPosition - writePosition);
+        }
+
+        // Note, if we fill the buffer up 100%, then write position == read position,
+        // which is the same as when the buffer is empty and everything in the buffer
+        // would be lost.
+        // Reserve 1 byte so that when the buffer is full the write position will trail
+        // the read position.
+        // Because of this reserve, and the above calculation, the true bytesAvailable 
+        // count can never be 0.
+        assert(bytesAvailable != 0);
+        bytesAvailable--;
+
+        // if there is sufficient space to write the buffer, send it
+        if (bytesAvailable >= requiredBufferSize)
+        {
+            PLOOPEDDATAFORMAT header = (PLOOPEDDATAFORMAT)(((BYTE*)Data->BufferAddress) + writePosition);
+
+            header->ByteCount = Length;
+            CopyMemory((((BYTE*)header) + sizeof(LOOPEDDATAFORMAT)), MidiData, Length);
+
+            // if a position provided is nonzero, use it, otherwise use the current QPC
+            if (Position)
             {
-                bytesAvailable = Data->BufferSize - (writePosition - readPosition);
+                header->Position = Position;
             }
-            else
+            else if (m_OverwriteZeroTimestamp)
             {
-                bytesAvailable = (readPosition - writePosition);
+                LARGE_INTEGER qpc{ 0 };
+                QueryPerformanceCounter(&qpc);
+                header->Position = qpc.QuadPart;
             }
 
-            // Note, if we fill the buffer up 100%, then write position == read position,
-            // which is the same as when the buffer is empty and everything in the buffer
-            // would be lost.
-            // Reserve 1 byte so that when the buffer is full the write position will trail
-            // the read position.
-            // Because of this reserve, and the above calculation, the true bytesAvailable 
-            // count can never be 0.
-            assert(bytesAvailable != 0);
-            bytesAvailable--;
-
-            // if there is sufficient space to write the buffer, send it
-            if (bytesAvailable >= requiredBufferSize)
-            {
-                PLOOPEDDATAFORMAT header = (PLOOPEDDATAFORMAT)(((BYTE*)Data->BufferAddress) + writePosition);
-
-                header->ByteCount = Length;
-                CopyMemory((((BYTE*)header) + sizeof(LOOPEDDATAFORMAT)), MidiData, Length);
-
-                // if a position provided is nonzero, use it, otherwise use the current QPC
-                if (Position)
-                {
-                    header->Position = Position;
-                }
-                else if (m_OverwriteZeroTimestamp)
-                {
-                    LARGE_INTEGER qpc{ 0 };
-                    QueryPerformanceCounter(&qpc);
-                    header->Position = qpc.QuadPart;
-                }
-
-                // update the write position and notify the other side that data is available.
-                InterlockedExchange((LONG*)Registers->WritePosition, newWritePosition);
-                RETURN_LAST_ERROR_IF(FALSE == SetEvent(m_MidiOut->WriteEvent.get()));
+            // update the write position and notify the other side that data is available.
+            InterlockedExchange((LONG*)Registers->WritePosition, newWritePosition);
+            RETURN_LAST_ERROR_IF(FALSE == SetEvent(m_MidiOut->WriteEvent.get()));
 
-                //if (!SetEvent(m_MidiOut->WriteEvent.get()))
-                //{
-                //    LOG_LAST_ERROR();
-                //    RETURN_LAST_ERROR_IF(true);
-                //}
+            //if (!SetEvent(m_MidiOut->WriteEvent.get()))
+            //{
+            //    LOG_LAST_ERROR();
+            //    RETURN_LAST_ERROR_IF(true);
+            //}
 
-                bufferSent = TRUE;
-            }
-            else
-            {
-                // relinquish the remainder of this processing slice and try again on the next
-                Sleep(0);
-            }
+            bufferSent = TRUE;
+        }
+        else
+        {
+            // relinquish the remainder of this processing slice and try again on the next
+            //Sleep(0);
+
+            // if you remove this line, you will get additional send *and* receive failures
+            // if you set it to Sleep(0), you will end up with missing messages if we're 
+            // spammed heavily
+            // If you set it to Sleep(1), there's more jitter, but all messages arrive.
+            Sleep(1);
         }
-        CATCH_LOG();
 
     }while (!bufferSent && --maxRetries > 0);