fdo#68961: Check visible range during scrolling, and re-paint if necessary.

Change-Id: I47383cc0c4cf0ec48ce621ba5acac33db44ba313

sc/source/ui/inc/tabview.hxx

@@ -208,6 +208,12 @@ private:
 
     void            PaintRangeFinderEntry (ScRangeFindData* pData, SCTAB nTab);
 
+    /**
+     * Check the visible grid area to see if the visible range has changed. If
+     * so, update the stored visible range, and re-paint the grid area.
+     */
+    void UpdateGrid();
+
 protected:
     void            UpdateHeaderWidth( const ScVSplitPos* pWhich = NULL,
                                         const SCROW* pPosY = NULL );

sc/source/ui/view/tabview.cxx

@@ -1236,6 +1236,8 @@ void ScTabView::ScrollX( long nDeltaX, ScHSplitPos eWhich, bool bUpdBars )
         if (pColOutline[eWhich]) pColOutline[eWhich]->ScrollPixel( nDiff );
         if (bUpdBars)
             UpdateScrollBars();
+        else
+            UpdateGrid();
     }
 
     if (nDeltaX==1 || nDeltaX==-1)
@@ -1321,6 +1323,8 @@ void ScTabView::ScrollY( long nDeltaY, ScVSplitPos eWhich, bool bUpdBars )
         if (pRowOutline[eWhich]) pRowOutline[eWhich]->ScrollPixel( nDiff );
         if (bUpdBars)
             UpdateScrollBars();
+        else
+            UpdateGrid();
     }
 
     if (nDeltaY==1 || nDeltaY==-1)

sc/source/ui/view/tabview3.cxx

@@ -2109,6 +2109,19 @@ void ScTabView::PaintRangeFinderEntry (ScRangeFindData* pData, const SCTAB nTab)
     }
 }
 
+void ScTabView::UpdateGrid()
+{
+    if (!aViewData.IsActive())
+        return;
+
+    if (!UpdateVisibleRange())
+        // Visible range hasn't changed. No need to re-paint.
+        return;
+
+    SC_MOD()->AnythingChanged();                // if visible area has changed
+    PaintGrid();
+}
+
 void ScTabView::PaintRangeFinder( long nNumber )
 {
     ScInputHandler* pHdl = SC_MOD()->GetInputHdl( aViewData.GetViewShell() );

sc/source/ui/view/tabview4.cxx

@@ -424,15 +424,7 @@ void ScTabView::UpdateScrollBars()
     }
 
     //      set visible area for online spelling
-
-    if ( aViewData.IsActive() )
-    {
-        if (UpdateVisibleRange())
-        {
-            SC_MOD()->AnythingChanged();                // if visible area has changed
-            PaintGrid();
-        }
-    }
+    UpdateGrid();
 }
 
 #ifndef HDR_SLIDERSIZE