Fix: MIDI parser — System Real-Time no longer corrupts running status

[sauloverissimo]

Summary

System Real-Time bytes (0xF8–0xFF) can legally appear anywhere in a MIDI byte stream — even between data bytes of a multi-byte message — and must not affect the parser's running status. The current parser handles them inside the ParserEmpty switch case, which means they first trigger a state reset (pstate_ = ParserEmpty) and overwrite incoming_message_ fields. This causes:

1. Channel corruption — a Timing Clock (0xF8) between NoteOn bytes shifts the channel to 8 (since 0xF8 & 0x0F = 8)
2. Lost messages — the in-progress multi-byte message is destroyed
3. SysEx corruption — RT bytes inside SysEx are stored as data instead of being dispatched

This is the root cause of #666 and #665.

The fix

Move System Real-Time handling to the very top of Parse(), before any state modification:

if(byte >= 0xF8)
{
    if(event_out != nullptr)
    {
        MidiEvent rt_event;
        rt_event.type    = SystemRealTime;
        rt_event.channel = 0;
        rt_event.srt_type = static_cast<SystemRealTimeType>(byte & kSystemRealTimeMask);
        *event_out = rt_event;
    }
    return true;
}

Uses a stack-local MidiEvent so pstate_, incoming_message_, and running_status_ are completely untouched. The early return means RT bytes are transparent to the rest of the parser — exactly as the MIDI 1.0 spec requires.

Tests

Added 4 new unit tests covering the scenarios that the existing runningStatSysRealtime test does not:

Test	What it covers
sysRealtimeMidMessage	Clock bytes interleaved within a NoteOn (between status/data0/data1)
sysRealtimeDuringSysEx	Clock byte inside a SysEx message — must not corrupt SysEx data
allSysRealtimeTypes	All 8 RT types (0xF8–0xFF) parse correctly with channel=0
runningStatusPreservedAfterRealtime	Running status NoteOn + RT + channel verification across multiple notes

All 154 tests pass (including the existing runningStatSysRealtime test).

Related

• Closes Midi In Clock not supported #666
• Closes Midi NoteOn Velocity 0 wrong channel #665
• Re-resolves MIDI - Clock messages may interfere with running status implementation #422 (the mid-message case was not covered by the original fix)
• Complements PR Feature: Midi - make it possible to handle 'SystemRealTime' events synchronously #643 (synchronous RT callback) — that PR adds a callback feature at the MidiHandler level, but the underlying parser bug still exists without this fix

[github-actions]

Test Results

154 tests  +4   154 ✅ +4   0s ⏱️ ±0s
  1 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 4ed3992. ± Comparison against base commit 9498417.