From b21fa47ec0435cbf96b80a2d3334a904204a5abf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Przemys=C5=82aw=20Czerpak?= <druzus@poczta.onet.pl>
Date: Wed, 10 May 2017 17:21:27 +0200
Subject: [PATCH] 2017-05-10 17:21 UTC+0200 Przemyslaw Czerpak
 (druzus/at/poczta.onet.pl)   * contrib/hbwin/olecore.c     + added functions
 which changes default method of NIL conversion to       OLE variant:         
 __oleVariantNil2Null( [<lNewNil2NullFlag>] ) -> <lPrevNil2NullFlag>       By
 default NIL values passed to foreign OLE code are converted to       VT_EMPTY
 variants. __oleVariantNil2Null( .t. ) changes this behavior       so NIL
 values are converted to VT_NULL variants.     ; Warning: This function was
 added for tests. Looks that it's expected                behavior for
 communication with MS-Excel and allows to use                NIL as default
 parameter value but potentially it may create                problems with
 some custom OLE interfaces so this modification                should be
 widely tested in real life before we change the                default
 behavior.

---
 ChangeLog.txt           | 15 +++++++++++++++
 contrib/hbwin/hbwin.hbx |  1 +
 contrib/hbwin/olecore.c | 32 +++++++++++++++++++++++++++++++-
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/ChangeLog.txt b/ChangeLog.txt
index eb4b78ae50..93213a791a 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -10,6 +10,21 @@
      * Change, ! Fix, % Optimization, + Addition, - Removal, ; Comment
  */
 
+2017-05-10 17:21 UTC+0200 Przemyslaw Czerpak (druzus/at/poczta.onet.pl)
+  * contrib/hbwin/olecore.c
+    + added functions which changes default method of NIL conversion to
+      OLE variant:
+         __oleVariantNil2Null( [<lNewNil2NullFlag>] ) -> <lPrevNil2NullFlag>
+      By default NIL values passed to foreign OLE code are converted to
+      VT_EMPTY variants. __oleVariantNil2Null( .t. ) changes this behavior
+      so NIL values are converted to VT_NULL variants.
+    ; Warning: This function was added for tests. Looks that it's expected
+               behavior for communication with MS-Excel and allows to use
+               NIL as default parameter value but potentially it may create
+               problems with some custom OLE interfaces so this modification
+               should be widely tested in real life before we change the
+               default behavior.
+
 2017-05-10 16:39 UTC+0200 Przemyslaw Czerpak (druzus/at/poczta.onet.pl)
   * contrib/hbwin/olecore.c
     - removed support for VT_DECIMAL and VT_PTR arrays from
diff --git a/contrib/hbwin/hbwin.hbx b/contrib/hbwin/hbwin.hbx
index 18b541cc2e..4b40e41295 100644
--- a/contrib/hbwin/hbwin.hbx
+++ b/contrib/hbwin/hbwin.hbx
@@ -432,6 +432,7 @@ DYNAMIC __oleIsDisp
 DYNAMIC __oleVariantGetType
 DYNAMIC __oleVariantGetValue
 DYNAMIC __oleVariantNew
+DYNAMIC __oleVariantNil2Null
 DYNAMIC __oleVariantNullDate
 DYNAMIC __wapi_DEVMODE_Get
 DYNAMIC __wapi_DEVMODE_New
diff --git a/contrib/hbwin/olecore.c b/contrib/hbwin/olecore.c
index 3014112c26..018788e2ba 100644
--- a/contrib/hbwin/olecore.c
+++ b/contrib/hbwin/olecore.c
@@ -86,6 +86,7 @@ typedef struct
 {
    HRESULT lOleError;
    HB_BOOL fNullDate;
+   HB_BOOL fNil2Null;
    int     iInit;
 } HB_OLEDATA, * PHB_OLEDATA;
 
@@ -93,6 +94,10 @@ static void hb_oleDataInit( void * cargo )
 {
    PHB_OLEDATA pOleData = ( PHB_OLEDATA ) cargo;
 
+   /* default settings: */
+   pOleData->fNullDate = HB_FALSE;
+   pOleData->fNil2Null = HB_FALSE;
+
 #if defined( HB_OS_WIN_CE )
    if( CoInitializeEx( NULL, COINIT_APARTMENTTHREADED ) == S_OK )
 #else
@@ -148,6 +153,17 @@ static HB_BOOL hb_oleGetNullDateFlag( void )
 }
 
 
+static void hb_oleSetNil2NullFlag( HB_BOOL fNil2Null )
+{
+   hb_getOleData()->fNil2Null = fNil2Null;
+}
+
+static HB_BOOL hb_oleGetNil2NullFlag( void )
+{
+   return hb_getOleData()->fNil2Null;
+}
+
+
 static void hb_olecore_init( void * cargo )
 {
    HB_SYMBOL_UNUSED( cargo );
@@ -799,6 +815,7 @@ static void hb_oleItemToVariantRef( VARIANT * pVariant, PHB_ITEM pItem,
       case HB_IT_TIMESTAMP:
       {
          double dDate = hb_itemGetTD( pItem );
+
          if( dDate == 0 && hb_oleGetNullDateFlag() )
          {
             V_VT( pVariant ) = VT_NULL;
@@ -896,6 +913,11 @@ static void hb_oleItemToVariantRef( VARIANT * pVariant, PHB_ITEM pItem,
          }
          break;
 
+      case HB_IT_NIL:
+         if( hb_oleGetNil2NullFlag() )
+            V_VT( pVariant ) = VT_NULL;
+         /* fallthrough */
+
       default:
          if( pVarRef )
          {
@@ -2602,7 +2624,7 @@ HB_FUNC( __OLEVARIANTNEW )
       hb_errRT_OLE( EG_ARG, 1018, 0, NULL, HB_ERR_FUNCNAME, NULL );
 }
 
-/* __oleVariantNullDate( [<lNewNullFlag>] ) -> <lPrevNullFlag> */
+/* __oleVariantNullDate( [<lNewNullDateFlag>] ) -> <lPrevNullDateFlag> */
 HB_FUNC( __OLEVARIANTNULLDATE )
 {
    hb_retl( hb_oleGetNullDateFlag() );
@@ -2610,6 +2632,14 @@ HB_FUNC( __OLEVARIANTNULLDATE )
       hb_oleSetNullDateFlag( hb_parl( 1 ) );
 }
 
+/* __oleVariantNil2Null( [<lNewNil2NullFlag>] ) -> <lPrevNil2NullFlag> */
+HB_FUNC( __OLEVARIANTNIL2NULL )
+{
+   hb_retl( hb_oleGetNil2NullFlag() );
+   if( HB_ISLOG( 1 ) )
+      hb_oleSetNil2NullFlag( hb_parl( 1 ) );
+}
+
 HB_CALL_ON_STARTUP_BEGIN( _hb_olecore_init_ )
    hb_vmAtInit( hb_olecore_init, NULL );
 HB_CALL_ON_STARTUP_END( _hb_olecore_init_ )