From 913244710ae72d6c5abce219d88bfb5ff4cd809c Mon Sep 17 00:00:00 2001
From: LexiconCode <CasterVoice@protonmail.com>
Date: Wed, 25 Feb 2026 21:11:42 -0600
Subject: [PATCH] Fix playString/playEvents hanging on DNS 16

Fix playString/playEvents hanging on DNS 16 by passing notify=1 in the
extra vtable parameter DNS 16 added to PlayString and PlayEvents.
Without it, PlaybackDone never fires and the message loop blocks
indefinitely.

Adds Dragon version detection at connect time to select the correct
calling convention.
---
 NatlinkSource/DragonCode.cpp | 90 +++++++++++++++++++++++++-----------
 NatlinkSource/DragonCode.h   |  6 +++
 2 files changed, 69 insertions(+), 27 deletions(-)

diff --git a/NatlinkSource/DragonCode.cpp b/NatlinkSource/DragonCode.cpp
index 2152b1ea..2e44b868 100644
--- a/NatlinkSource/DragonCode.cpp
+++ b/NatlinkSource/DragonCode.cpp
@@ -1728,6 +1728,15 @@ BOOL CDragonCode::natConnect( IServiceProvider * pIDgnSite, BOOL bUseThreads )
 		__uuidof(IDgnSREngineControl), (void**)&m_pIDgnSREngineControl );
 	RETURNIFERROR( rc, "ISRCentral::QueryInterface(IDgnSREngineControl)" );
 
+	// Detect Dragon version — DNS 16 has different COM calling conventions.
+	{
+		WORD wMajor = 0, wMinor = 0, wBuild = 0;
+		rc = m_pIDgnSREngineControl->GetVersion(&wMajor, &wMinor, &wBuild);
+		if (SUCCEEDED(rc)) {
+			m_dragonMajorVersion = wMajor;
+		}
+	}
+
 	// get the speech services interfaces
 
 	IDgnSpeechServicesPtr pSpchSvc;
@@ -2015,32 +2024,37 @@ BOOL CDragonCode::playString( const char * pszKeys, DWORD dwFlags )
 	DWORD dwClientCode = ++dwUnique;
 
 	DWORD dwNumUndo=0;
-		
-
-	#ifdef UNICODE
-
-
-	rc = m_pIDgnSSvcOutputEventA->PlayString(
-		pszKeys,	// string to send
-		dwFlags,		// flags
-		0xFFFFFFFF,		// delay (-1 for app specific delay)
-		dwClientCode,	// to identify which WM_PLAYBACK is ours
-		&dwNumUndo );
-
-	int const inputCodePage = CP_UTF8;
-	int const outputCodePage = 1252;
-
-
 
+	if (m_dragonMajorVersion >= 16) {
+		// DNS 16 added a 6th parameter to PlayString that controls whether
+		// the PlaybackDone callback fires.  Passing 0 = fire-and-forget
+		// (no callback), non-zero = notify via PlaybackDone.
+		// The callee does ret 28 (this + 6 params), so we must use raw
+		// vtable calls to avoid ESP corruption with the 5-param header.
+		void** vtable = *(void***)((IUnknown*)m_pIDgnSSvcOutputEvent);
+		void* pfnPlayString = vtable[4];  // slot 4 = PlayString
+		void* pThis = (void*)m_pIDgnSSvcOutputEvent;
+		DWORD* pNumUndo = &dwNumUndo;
+		HRESULT comRc;
+
+		__asm {
+			push 1                    // [5] DWORD dwNotify — non-zero for PlaybackDone
+			push pNumUndo             // [4] DWORD* pNumUndo
+			push dwClientCode         // [3] DWORD dwClientCode
+			push 0xFFFFFFFF           // [2] DWORD dwDelay (-1)
+			push dwFlags              // [1] DWORD dwFlags
+			push pszKeys              // [0] const char* pszKeys
+			push pThis                // this
+			call pfnPlayString
+			mov comRc, eax
+		}
 
-	#else
+		rc = comRc;
+	} else {
+		// DNS 13/15: standard 5-param COM call
 		rc = m_pIDgnSSvcOutputEvent->PlayString(
-			pszKeys, 	  // string to send
-			dwFlags,	  // flags
-			0xFFFFFFFF,   // delay (-1 for app specific delay)
-			dwClientCode, // to identify which WM_PLAYBACK is ours
-			&dwNumUndo ); // not used (number of backspaces needed to undo)
-	#endif
+			pszKeys, dwFlags, 0xFFFFFFFF, dwClientCode, &dwNumUndo );
+	}
 
 
 	RETURNIFERROR( rc, "IDgnSSvcOutputEvent::PlayString" );
@@ -2586,10 +2600,32 @@ BOOL CDragonCode::playEvents( DWORD dwCount, HOOK_EVENTMSG * pEvents )
 	static DWORD dwUnique = 1;
 	DWORD dwClientCode = ++dwUnique;
 
-	rc = m_pIDgnSSvcOutputEvent->PlayEvents(
-		dwCount, pEvents,
-		0xFFFFFFFF,   	// delay (-1 for app specific delay)
-		dwClientCode ); // to identify which WM_PLAYBACK is ours
+	if (m_dragonMajorVersion >= 16) {
+		// DNS 16 added a 5th parameter to PlayEvents that controls whether
+		// the PlaybackDone callback fires (same as PlayString's 6th param).
+		// The callee does ret 24 (this + 5 params), so raw vtable call needed.
+		void** vtable = *(void***)((IUnknown*)m_pIDgnSSvcOutputEvent);
+		void* pfnPlayEvents = vtable[6];  // slot 6 = PlayEvents
+		void* pThis = (void*)m_pIDgnSSvcOutputEvent;
+		HRESULT comRc;
+
+		__asm {
+			push 1                    // [4] DWORD dwNotify — non-zero for PlaybackDone
+			push dwClientCode         // [3] DWORD dwClientCode
+			push 0xFFFFFFFF           // [2] DWORD dwDelay (-1)
+			push pEvents              // [1] const HOOK_EVENTMSG*
+			push dwCount              // [0] DWORD dwCount
+			push pThis                // this
+			call pfnPlayEvents
+			mov comRc, eax
+		}
+
+		rc = comRc;
+	} else {
+		// DNS 13/15: standard 4-param COM call
+		rc = m_pIDgnSSvcOutputEvent->PlayEvents(
+			dwCount, pEvents, 0xFFFFFFFF, dwClientCode );
+	}
 	RETURNIFERROR( rc, "IDgnSSvcOutputEvent::PlayEvents" );
 
 	// Now we want to wait until the playback finishes or is aborted
diff --git a/NatlinkSource/DragonCode.h b/NatlinkSource/DragonCode.h
index 230073b4..3b1b41ed 100644
--- a/NatlinkSource/DragonCode.h
+++ b/NatlinkSource/DragonCode.h
@@ -28,6 +28,7 @@ class CDragonCode
 	CDragonCode() {
 		m_hMsgWnd = NULL;
 		m_dwKey = 0;
+		m_dragonMajorVersion = 13;
 		m_pBeginCallback = NULL;
 		m_pChangeCallback = NULL;
 		m_pFirstGramObj = NULL;
@@ -189,6 +190,11 @@ class CDragonCode
 	// the key for unregistering our engine sink (a SAPI thing)
 	DWORD m_dwKey;
 
+	// Dragon major version (e.g. 13, 15, 16).  Detected at connect time
+	// via IDgnSREngineControl::GetVersion.  DNS 16 has different COM
+	// calling conventions for PlayString and PlayEvents.
+	DWORD m_dragonMajorVersion;
+
 	// the name of the log file (or en empty string if not known).  We
 	// assume that this will be less than the maximum path and file name
 	// under Windows.