Implemented:

include/tab.h

@@ -9,29 +9,35 @@
 
 typedef struct tagTAB_ITEM
 {
-	UINT  mask;
-	DWORD	dwState;
-    LPSTR	pszText;
-	INT   cchTextMax;
-    INT	iImage;
-    LPARAM	lParam;
-    RECT   	rect;		/* bounding rectangle of the item */
+  UINT   mask;
+  DWORD  dwState;
+  LPSTR  pszText;
+  INT    cchTextMax;
+  INT    iImage;
+  LPARAM lParam;
+  RECT   rect;    /* bounding rectangle of the item relative to the
+		   * leftmost item (the leftmost item, 0, would have a 
+		   * "left" member of 0 in this rectangle) */
 } TAB_ITEM;
 
 typedef struct tagTAB_INFO
 {
-    UINT	    uNumItem;	/* number of tab items */
-    INT	    nHeight;	/* height of the tab row */
-    HFONT	    hFont;		/* handle to the current font */
-    HCURSOR	hcurArrow;	/* handle to the current cursor */
-	HIMAGELIST  himl;       /* handle to a image list (may be 0) */
-	HWND		hwndToolTip; /* handle to tab's tooltip */
-	UINT		cchTextMax;
-    INT	    iSelected;	/* the currently selected item */
-    INT	    uFocus;		/* item which has the focus */
-    TAB_ITEM	*items;		/* pointer to an array of TAB_ITEM's */
-    RECT	    rect;
-    BOOL	    DoRedraw;	/* flag for redrawing when tab contents is changed*/
+  UINT       uNumItem;        /* number of tab items */
+  INT        tabHeight;       /* height of the tab row */
+  HFONT      hFont;           /* handle to the current font */
+  HCURSOR    hcurArrow;       /* handle to the current cursor */
+  HIMAGELIST himl;            /* handle to a image list (may be 0) */
+  HWND       hwndToolTip;     /* handle to tab's tooltip */
+  UINT       cchTextMax;
+  INT        leftmostVisible; /* Used for scrolling, this member contains
+			       * the index of the first visible item */
+  INT        iSelected;       /* the currently selected item */
+  INT        uFocus;          /* item which has the focus */
+  TAB_ITEM*  items;           /* pointer to an array of TAB_ITEM's */
+  BOOL       DoRedraw;        /* flag for redrawing when tab contents is changed*/
+  BOOL       needsScrolling;  /* TRUE if the size of the tabs is greater than 
+			       * the size of the control */
+  HWND       hwndUpDown;      /* Updown control used for scrolling */
 } TAB_INFO;