diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index a1e8b6f105..dd6e2904e3 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -8,6 +8,39 @@
    2008-12-31 13:59 UTC+0100 Foo Bar (foo.bar foobar.org)
 */
 
+2008-10-11 04:56 UTC+0200 Przemyslaw Czerpak (druzus/at/priv.onet.pl)
+  * harbour/include/hbapigt.h
+  * harbour/source/rtl/gtapi.c
+    + added C functions hb_gtLock() and hb_gtUnlock()
+      They block current GT for other threads
+
+  * harbour/source/rtl/gtfunc.c
+    + added PRG functions hb_gtLock() and hb_gtUnlock()
+      They block current GT for other threads - be careful using them
+      and always unlock locked GT
+
+  * harbour/source/rtl/scroll.c
+    + added HB_SCROLL() function - it works like SCROLL() but supports
+      2 additional parameters: color and erase char. It's stateless and
+      atomic in GT access
+
+  * harbour/source/rtl/tbrowse.prg
+    * use HB_SCROLL() instead of SCROLL(). Now whole TBROWSE class
+      does not depend on other thread screen output and does not
+      set any GT variables except of cursor positioning to active
+      cell when it's enabled
+
+  * harbour/source/rtl/memoedit.prg
+  * harbour/source/rtl/tgetlist.prg
+  * harbour/source/rtl/tlabel.prg
+  * harbour/source/rtl/listbox.prg
+  * harbour/source/rtl/tmenusys.prg
+  * harbour/source/rtl/achoice.prg
+  * harbour/source/rtl/profiler.prg
+  * harbour/source/rtl/teditor.prg
+    * use atomic stateless functions when possible - this code should
+      be checked and updated by some who know it.
+
 2008-10-11 03:24 UTC+0200 Przemyslaw Czerpak (druzus/at/priv.onet.pl)
   * harbour/source/rtl/scrollbr.prg
   * harbour/source/rtl/getsys.prg
diff --git a/harbour/include/hbapigt.h b/harbour/include/hbapigt.h
index 75db998938..a277dad02f 100644
--- a/harbour/include/hbapigt.h
+++ b/harbour/include/hbapigt.h
@@ -142,6 +142,8 @@ typedef struct
 
 extern HB_EXPORT ERRCODE hb_gtInit( HB_FHANDLE hFilenoStdin, HB_FHANDLE hFilenoStdout, HB_FHANDLE hFilenoStderr );
 extern HB_EXPORT ERRCODE hb_gtExit( void );
+extern HB_EXPORT ERRCODE hb_gtLock( void );
+extern HB_EXPORT ERRCODE hb_gtUnlock( void );
 extern HB_EXPORT ERRCODE hb_gtBox( SHORT uiTop, SHORT uiLeft, SHORT uiBottom, SHORT uiRight, BYTE * pbyFrame );
 extern HB_EXPORT ERRCODE hb_gtBoxD( SHORT uiTop, SHORT uiLeft, SHORT uiBottom, SHORT uiRight );
 extern HB_EXPORT ERRCODE hb_gtBoxS( SHORT uiTop, SHORT uiLeft, SHORT uiBottom, SHORT uiRight );
diff --git a/harbour/source/rtl/achoice.prg b/harbour/source/rtl/achoice.prg
index b8561a3f7f..ddc9473724 100644
--- a/harbour/source/rtl/achoice.prg
+++ b/harbour/source/rtl/achoice.prg
@@ -197,7 +197,7 @@ FUNCTION AChoice( nTop, nLeft, nBottom, nRight, acItems, xSelect, xUserFunc, nPo
             ELSE
                DispBegin()
                DispLine( acItems[ nPos ], nTop + ( nPos - nAtTop ), nLeft, Eval( bSelect, alSelect[ nPos ] ), .F., nNumCols )
-               Scroll( nTop, nLeft, nBottom, nRight, ( nNewPos - ( nAtTop + nNumRows - 1 ) ) )
+               hb_scroll( nTop, nLeft, nBottom, nRight, ( nNewPos - ( nAtTop + nNumRows - 1 ) ) )
                nAtTop := nNewPos
                nPos   := Max( nPos, nAtTop + nNumRows - 1 )
                DO WHILE nPos > nNewPos
@@ -237,7 +237,7 @@ FUNCTION AChoice( nTop, nLeft, nBottom, nRight, acItems, xSelect, xUserFunc, nPo
             ELSE
                DispBegin()
                DispLine( acItems[ nPos ], nTop + ( nPos - nAtTop ), nLeft, Eval( bSelect, alSelect[ nPos ] ), .F., nNumCols )
-               Scroll( nTop, nLeft, nBottom, nRight, ( nNewPos - ( nAtTop + nNumRows - 1 ) ) )
+               hb_scroll( nTop, nLeft, nBottom, nRight, ( nNewPos - ( nAtTop + nNumRows - 1 ) ) )
                nAtTop := nNewPos - nNumRows + 1
                nPos   := Max( nPos, nAtTop )
                DO WHILE nPos < nNewPos
diff --git a/harbour/source/rtl/gtapi.c b/harbour/source/rtl/gtapi.c
index 0022a9adff..44f7d15ab6 100644
--- a/harbour/source/rtl/gtapi.c
+++ b/harbour/source/rtl/gtapi.c
@@ -139,6 +139,40 @@ HB_EXPORT ERRCODE hb_gtExit( void )
    return SUCCESS;
 }
 
+HB_EXPORT ERRCODE hb_gtLock( void )
+{
+   ERRCODE errCode = FAILURE;
+   PHB_GT pGT;
+
+   HB_TRACE(HB_TR_DEBUG, ("hb_gtLock()"));
+
+   pGT = hb_gt_Base();
+   if( pGT )
+   {
+      if( HB_GTSELF_LOCK( pGT ) )
+         errCode = SUCCESS;
+      hb_gt_BaseFree( pGT );
+   }
+   return errCode;
+}
+
+HB_EXPORT ERRCODE hb_gtUnlock( void )
+{
+   ERRCODE errCode = FAILURE;
+   PHB_GT pGT;
+
+   HB_TRACE(HB_TR_DEBUG, ("hb_gtUnlock()"));
+
+   pGT = hb_gt_Base();
+   if( pGT )
+   {
+      HB_GTSELF_UNLOCK( pGT );
+      errCode = SUCCESS;
+      hb_gt_BaseFree( pGT );
+   }
+   return errCode;
+}
+
 HB_EXPORT int hb_gtReadKey( int iEventMask )
 {
    int iKey = 0;
diff --git a/harbour/source/rtl/gtfunc.c b/harbour/source/rtl/gtfunc.c
index 78cc14a50f..a38243d0a9 100644
--- a/harbour/source/rtl/gtfunc.c
+++ b/harbour/source/rtl/gtfunc.c
@@ -145,3 +145,13 @@ HB_FUNC( HB_GFXTEXT )
                  hb_parni( 5 ) /* nSize  */,
                  hb_parni( 6 ) /* nWidth */ );
 }
+
+HB_FUNC( HB_GTLOCK )
+{
+   hb_retl( hb_gtLock() );
+}
+
+HB_FUNC( HB_GTUNLOCK )
+{
+   hb_gtUnlock();
+}
diff --git a/harbour/source/rtl/listbox.prg b/harbour/source/rtl/listbox.prg
index f9954513cf..82de754605 100644
--- a/harbour/source/rtl/listbox.prg
+++ b/harbour/source/rtl/listbox.prg
@@ -236,6 +236,7 @@ METHOD display() CLASS LISTBOX
    LOCAL cColor4
    LOCAL cColor3
    LOCAL cColorAny
+   LOCAL cColorScrl
    LOCAL nTop := ::nTop
    LOCAL nLeft := ::nLeft
    LOCAL nSize := ::nRight - nLeft + 1
@@ -273,20 +274,26 @@ METHOD display() CLASS LISTBOX
    IF ::lIsOpen
       IF !Empty( cHotBox )
 
-         nOldRow := Row()
-         nOldCol := Col()
-         cOldColor := SetColor()
-
-         SetColor( hb_ColorIndex( ::cColorSpec, 4 ) )
-         Scroll( nTop, nLeft, ::nBottom, ::nRight )
-         DispBox( nTop, nLeft, ::nBottom, ::nRight, cHotBox )
+         cColorScrl := hb_ColorIndex( ::cColorSpec, 4 )
+         hb_scroll( nTop, nLeft, ::nBottom, ::nRight,,, cColorScrl )
+         hb_dispBox( nTop, nLeft, ::nBottom, ::nRight, cHotBox, cColorScrl )
 
          IF ::oVScroll != NIL
-            ::oVScroll:display()
-         ENDIF
 
-         SetColor( cOldColor )
-         SetPos( nOldRow, nOldCol )
+            /* Is it necessary to save, set and restore color and cursor
+             * position for ::oVScroll:display() or we can remove it?
+             */
+            nOldRow := Row()
+            nOldCol := Col()
+            cOldColor := SetColor()
+            SetColor( cColorScrl )
+
+            ::oVScroll:display()
+
+            SetColor( cOldColor )
+            SetPos( nOldRow, nOldCol )
+
+         ENDIF
 
          nTop++
          nLeft++
diff --git a/harbour/source/rtl/memoedit.prg b/harbour/source/rtl/memoedit.prg
index ed5f781253..0e8b8459ed 100644
--- a/harbour/source/rtl/memoedit.prg
+++ b/harbour/source/rtl/memoedit.prg
@@ -153,16 +153,17 @@ METHOD KeyboardHook( nKey ) CLASS HBMemoEditor
       IF nKey == K_ESC
          IF ::lDirty .AND. Set( _SET_SCOREBOARD )
             cBackScr := SaveScreen( ::nTop, ::nRight - 18, ::nTop, ::nRight )
-            
+
             nRow := Row()
             nCol := Col()
-            @ ::nTop, ::nRight - 18 SAY "Abort Edit? (Y/N)"
-            
+            hb_dispOutAt( ::nTop, ::nRight - 18, "Abort Edit? (Y/N)" )
+            SetPos( ::nTop, ::nRight - 1 )
+
             nYesNoKey := Inkey( 0 )
-            
+
             RestScreen( ::nTop, ::nRight - 18, ::nTop, ::nRight, cBackScr )
             SetPos( nRow, nCol )
-            
+
             IF Upper( Chr( nYesNoKey ) ) == "Y"
                ::lSaved := .F.
                ::lExitEdit := .T.
@@ -238,7 +239,7 @@ METHOD xDo( nStatus ) CLASS HBMemoEditor
    LOCAL nOldRow := ::Row()
    LOCAL nOldCol := ::Col()
    LOCAL nOldCur := SetCursor()
-   
+
    LOCAL xResult := Do( ::xUserFunction, nStatus, ::nRow, ::nCol - 1 )
 
    IF ! ISNUMBER( xResult )
diff --git a/harbour/source/rtl/profiler.prg b/harbour/source/rtl/profiler.prg
index 5bd33938ec..94712a9141 100644
--- a/harbour/source/rtl/profiler.prg
+++ b/harbour/source/rtl/profiler.prg
@@ -149,7 +149,7 @@ PROCEDURE Main()
 
 STATIC PROCEDURE DrawScreen( cTitle )
 
-   Scroll()
+   CLEAR SCREEN
 
    @ 0, 0 SAY PadR( cTitle, MaxCol() + 1 ) COLOR "N/W"
 
diff --git a/harbour/source/rtl/scroll.c b/harbour/source/rtl/scroll.c
index e9b5dad899..2b41fea859 100644
--- a/harbour/source/rtl/scroll.c
+++ b/harbour/source/rtl/scroll.c
@@ -108,3 +108,79 @@ HB_FUNC( SCROLL )
                 ( SHORT ) hb_parni( 5 ), /* Defaults to zero on bad type */
                 ( SHORT ) hb_parni( 6 ) ); /* Defaults to zero on bad type */
 }
+
+HB_FUNC( HB_SCROLL )
+{
+   int iMaxRow = hb_gtMaxRow();
+   int iMaxCol = hb_gtMaxCol();
+
+   int iTop;
+   int iLeft;
+   int iBottom;
+   int iRight;
+   int iColor;
+   int iChar;
+
+   /* Enforce limits of (0,0) to (MAXROW(),MAXCOL()) */
+
+   iTop = hb_parni( 1 ); /* Defaults to zero on bad type */
+   if( iTop < 0 )
+      iTop = 0;
+   else if( iTop > iMaxRow )
+      iTop = iMaxRow;
+
+   iLeft = hb_parni( 2 ); /* Defaults to zero on bad type */
+   if( iLeft < 0 )
+      iLeft = 0;
+   else if( iLeft > iMaxCol )
+      iLeft = iMaxCol;
+
+   if( ISNUM( 3 ) )
+   {
+      iBottom = hb_parni( 3 );
+      if( iBottom < 0 )
+         iBottom = 0;
+      else if( iBottom > iMaxRow )
+         iBottom = iMaxRow;
+   }
+   else
+      iBottom = iMaxRow;
+
+   if( ISNUM( 4 ) )
+   {
+      iRight = hb_parni( 4 );
+      if( iRight < 0 )
+         iRight = 0;
+      else if( iRight > iMaxCol )
+         iRight = iMaxCol;
+   }
+   else
+      iRight = iMaxCol;
+
+   if( ISNUM( 7 ) )
+      iColor = hb_parni( 7 );
+   else if( ISCHAR( 7 ) )
+   {
+      iColor = hb_gtColorToN( hb_parc( 7 ) );
+      if( iColor == -1 )
+         iColor = hb_gtColorToN( "W/N" );
+   }
+   else
+      iColor = hb_gtGetClearColor();
+
+   if( ISNUM( 8 ) )
+      iChar = hb_parni( 8 );
+   else if( ISCHAR( 8 ) )
+      iChar = ( UCHAR ) hb_parc( 8 )[0];
+   else
+      iChar = hb_gtGetClearChar();
+
+   hb_gtScrollEx( iTop,
+                  iLeft,
+                  iBottom,
+                  iRight,
+                  ( BYTE ) iColor,
+                  ( BYTE ) iChar,
+                  hb_parni( 5 ), /* Defaults to zero on bad type */
+                  hb_parni( 6 ) ); /* Defaults to zero on bad type */
+}
diff --git a/harbour/source/rtl/tbrowse.prg b/harbour/source/rtl/tbrowse.prg
index 89bc6c4a84..0305fc2ba8 100644
--- a/harbour/source/rtl/tbrowse.prg
+++ b/harbour/source/rtl/tbrowse.prg
@@ -572,7 +572,6 @@ METHOD scrollBuffer( nRows ) CLASS TBROWSE
 
    LOCAL nRowCount := ::rowCount
    LOCAL aValues, aColors
-   LOCAL cOldColor
 
    /* Store last scroll value to chose refresh order. [druzus] */
    ::nLastScroll := nRows
@@ -580,11 +579,9 @@ METHOD scrollBuffer( nRows ) CLASS TBROWSE
    IF nRows >= nRowCount .OR. nRows <= -nRowCount
       AFill( ::aCellStatus, .F. )
    ELSE
-      cOldColor := SetColor( ::colorValue( _TBC_CLR_STANDARD ) )
-      Scroll( ::n_Top + ::nHeadHeight + iif( ::lHeadSep, 1, 0 ), ::n_Left, ;
-              ::n_Bottom - ::nFootHeight - iif( ::lFootSep, 1, 0 ), ::n_Right, ;
-              nRows )
-      SetColor( cOldColor )
+      hb_scroll( ::n_Top + ::nHeadHeight + iif( ::lHeadSep, 1, 0 ), ::n_Left, ;
+                 ::n_Bottom - ::nFootHeight - iif( ::lFootSep, 1, 0 ), ::n_Right, ;
+                 nRows,, ::colorValue( _TBC_CLR_STANDARD ) )
       IF nRows > 0
          DO WHILE --nRows >= 0
             aValues := ::aCellValues[ 1 ]
diff --git a/harbour/source/rtl/teditor.prg b/harbour/source/rtl/teditor.prg
index 598bb13f2f..d95188323a 100644
--- a/harbour/source/rtl/teditor.prg
+++ b/harbour/source/rtl/teditor.prg
@@ -405,7 +405,6 @@ METHOD display() CLASS HBEditor
    LOCAL i
    LOCAL nOCol := ::Col()
    LOCAL nORow := ::Row()
-   LOCAL cOldColor
 
    DispBegin()
 
@@ -415,9 +414,7 @@ METHOD display() CLASS HBEditor
 
    // Clear rest of editor window (needed when deleting lines of text)
    IF ::naTextLen < ::nNumRows
-      cOldColor := SetColor( ::cColorSpec )
-      Scroll( ::nTop + ::naTextLen, ::nLeft, ::nBottom, ::nRight )
-      SetColor( cOldColor )
+      hb_scroll( ::nTop + ::naTextLen, ::nLeft, ::nBottom, ::nRight,,, ::cColorSpec )
    ENDIF
 
    ::SetPos( nORow, nOCol )
@@ -470,7 +467,7 @@ METHOD MoveCursor( nKey ) CLASS HBEditor
       ENDIF
       IF ::Row() == ::nBottom
          IF ::nRow < ::naTextLen
-            Scroll( ::nTop, ::nLeft, ::nBottom, ::nRight, 1 )
+            hb_scroll( ::nTop, ::nLeft, ::nBottom, ::nRight, 1 )
             ::nFirstRow++
             ::nRow++
             ::RefreshLine()
@@ -513,7 +510,7 @@ METHOD MoveCursor( nKey ) CLASS HBEditor
       ENDIF
       IF ::Row() == ::nTop
          IF ::nRow > 1
-            Scroll( ::nTop, ::nLeft, ::nBottom, ::nRight, -1 )
+            hb_scroll( ::nTop, ::nLeft, ::nBottom, ::nRight, -1 )
             ::nFirstRow--
             ::nRow--
             ::RefreshLine()
@@ -548,7 +545,7 @@ METHOD MoveCursor( nKey ) CLASS HBEditor
    CASE nKey == K_RIGHT
       IF ::Col() == ::nRight
          IF ::nCol <= iif( ::lWordWrap, ::nWordWrapCol, ::LineLen( ::nRow ) )
-            Scroll( ::nTop, ::nLeft, ::nBottom, ::nRight,, 1 )
+            hb_scroll( ::nTop, ::nLeft, ::nBottom, ::nRight,, 1 )
             ::nFirstCol++
             ::nCol++
             ::RefreshColumn()
@@ -570,7 +567,7 @@ METHOD MoveCursor( nKey ) CLASS HBEditor
    CASE nKey == K_LEFT
       IF ::Col() == ::nLeft
          IF ::nCol > 1
-            Scroll( ::nTop, ::nLeft, ::nBottom, ::nRight,, -1 )
+            hb_scroll( ::nTop, ::nLeft, ::nBottom, ::nRight,, -1 )
             ::nFirstCol--
             ::nCol--
             ::RefreshColumn()
@@ -1026,14 +1023,14 @@ METHOD New( cString, nTop, nLeft, nBottom, nRight, lEditMode, nLineLength, nTabS
    IF ::nFirstCol >  ::LineLen( ::nRow ) + 1
       ::nFirstCol := ::LineLen( ::nRow ) + 1
    ENDIF
-   
+
    IF ( ::nFirstRow + nWndRow ) > ::naTextLen
       DO WHILE ( ::nFirstRow + ( --nWndRow ) ) > ::naTextLen
       ENDDO
    ENDIF
 
    // Empty area of screen which will hold editor window
-   Scroll( nTop, nLeft, nBottom, nRight )
+   hb_scroll( nTop, nLeft, nBottom, nRight )
 
    // Set cursor upper left corner
    //::SetPos( ::nTop, ::nLeft )
diff --git a/harbour/source/rtl/tgetlist.prg b/harbour/source/rtl/tgetlist.prg
index 5f96121136..0bb36a995b 100644
--- a/harbour/source/rtl/tgetlist.prg
+++ b/harbour/source/rtl/tgetlist.prg
@@ -187,7 +187,7 @@ METHOD ReadModal() CLASS HBGetList
          cMsgColor := GetClrPair( SetColor(), 1 )
       ENDIF
 
-      Scroll( nMsgRow, nMsgLeft, nMsgRow, nMsgRight )
+      hb_scroll( nMsgRow, nMsgLeft, nMsgRow, nMsgRight )
 
       ::cMsgSaveS := SaveScreen( nMsgRow, nMsgLeft, nMsgRow, nMsgRight )
    ENDIF
diff --git a/harbour/source/rtl/tlabel.prg b/harbour/source/rtl/tlabel.prg
index cc8e2b4c8d..57ff3e96e0 100644
--- a/harbour/source/rtl/tlabel.prg
+++ b/harbour/source/rtl/tlabel.prg
@@ -332,7 +332,7 @@ METHOD SampleLabels() CLASS HBLabelForm
       nGetKey := Inkey( 0 )
       @ Row(), Col() SAY Chr( nGetKey )
       IF Row() == MaxRow()
-         Scroll( 0, 0, MaxRow(), MaxCol(), 1 )
+         hb_scroll( 0, 0, MaxRow(), MaxCol(), 1 )
          @ MaxRow(), 0 SAY ""
       ELSE
          @ Row() + 1, 0 SAY ""
diff --git a/harbour/source/rtl/tmenusys.prg b/harbour/source/rtl/tmenusys.prg
index 00e384d78e..adc88781b6 100644
--- a/harbour/source/rtl/tmenusys.prg
+++ b/harbour/source/rtl/tmenusys.prg
@@ -126,9 +126,9 @@ METHOD Modal( nSelection, nMsgRow, nMsgLeft, nMsgRight, cMsgColor, GetList ) CLA
    LOCAL bKeyBlock
    LOCAL lSubMenu
 
-   ::nOldRow    := Row()  
-   ::nOldCol    := Col()  
-   ::nOldCursor := SetCursor( SC_NONE )  
+   ::nOldRow    := Row()
+   ::nOldCol    := Col()
+   ::nOldCursor := SetCursor( SC_NONE )
 
    ::nMsgRow    := nMsgRow
    ::nMsgLeft   := nMsgLeft
@@ -143,7 +143,7 @@ METHOD Modal( nSelection, nMsgRow, nMsgLeft, nMsgRight, cMsgColor, GetList ) CLA
          ::cMsgColor := GetClrPair( SetColor(), 1 )
       ENDIF
 
-      Scroll( ::nMsgRow, ::nMsgLeft, ::nMsgRow, ::nMsgRight )
+      hb_scroll( ::nMsgRow, ::nMsgLeft, ::nMsgRow, ::nMsgRight )
 
       ::cMsgSaveS := SaveScreen( ::nMsgRow, ::nMsgLeft, ::nMsgRow, ::nMsgRight )
 
@@ -327,7 +327,7 @@ METHOD Modal( nSelection, nMsgRow, nMsgLeft, nMsgRight, cMsgColor, GetList ) CLA
             IF ::oMenu:ClassName() == "POPUPMENU"
                ::oMenu:close()
             ENDIF
-            
+
             nReturn := -1 // Bail out if at the top menu item
             EXIT