tdf#102139 : prevent the notebookbar from switching to empty tab

Change-Id: I0b463fef98d7597c9b7f22ee84701519a0f2b575
Reviewed-on: https://gerrit.libreoffice.org/33100Reviewed-by: Szymon Kłos <eszkadev@gmail.com>
Tested-by: Szymon Kłos <eszkadev@gmail.com>

include/vcl/tabctrl.hxx

@@ -68,7 +68,7 @@ protected:
     SAL_DLLPRIVATE Rectangle    ImplGetTabRect( sal_uInt16 nPos, long nWidth = -1, long nHeight = -1 );
     SAL_DLLPRIVATE void         ImplChangeTabPage( sal_uInt16 nId, sal_uInt16 nOldId );
     SAL_DLLPRIVATE bool         ImplPosCurTabPage();
-    SAL_DLLPRIVATE void         ImplActivateTabPage( bool bNext );
+    virtual void                ImplActivateTabPage( bool bNext );
     SAL_DLLPRIVATE void         ImplShowFocus();
     SAL_DLLPRIVATE void         ImplDrawItem(vcl::RenderContext& rRenderContext, ImplTabItem* pItem,
                                              const Rectangle& rCurRect, bool bFirstInGroup,
@@ -208,6 +208,7 @@ public:
 protected:
     virtual bool ImplPlaceTabs( long nWidth ) override;
     virtual void ImplPaint(vcl::RenderContext& rRenderContext, const Rectangle& rRect) override;
+    virtual void ImplActivateTabPage( bool bNext ) override;
 
 private:
     bool bLastContextWasSupported;

vcl/source/control/tabctrl.cxx

@@ -2288,6 +2288,39 @@ void NotebookbarTabControl::SetCurPageId( sal_uInt16 nPageId )
         TabControl::SetCurPageId( nPageId );
 }
 
+void NotebookbarTabControl::ImplActivateTabPage( bool bNext )
+{
+    sal_uInt16 nCurPos = GetPagePos( GetCurPageId() );
+
+    if ( bNext && nCurPos + 1 < GetPageCount() )
+    {
+        sal_uInt16 nOldPos = nCurPos;
+        nCurPos++;
+
+        ImplTabItem* pItem = &mpTabCtrlData->maItemList[nCurPos];
+        while ( !pItem->mbEnabled && nCurPos + 1 < GetPageCount())
+        {
+            nCurPos++;
+            pItem = &mpTabCtrlData->maItemList[nCurPos];
+        }
+
+        if ( !pItem->mbEnabled )
+            nCurPos = nOldPos;
+    }
+    else if ( !bNext && nCurPos )
+    {
+        nCurPos--;
+        ImplTabItem* pItem = &mpTabCtrlData->maItemList[nCurPos];
+        while ( nCurPos && !pItem->mbEnabled )
+        {
+            nCurPos--;
+            pItem = &mpTabCtrlData->maItemList[nCurPos];
+        }
+    }
+
+    SelectTabPage( TabControl::GetPageId( nCurPos ) );
+}
+
 sal_uInt16 NotebookbarTabControl::GetHeaderHeight()
 {
     return m_nHeaderHeight;