sc lok: Make the FmFormView we need for drawinglayer persistent.

Based on Marco Cecchetti's research - thanks! :-)

Change-Id: I579b6c8e54311a679f5d684f7ca1e2d7373d0ec9

sc/source/ui/inc/gridwin.hxx

@@ -38,6 +38,7 @@ namespace sc {
     struct SpellCheckContext;
 }
 
+class FmFormView;
 struct ScTableInfo;
 class ScDPObject;
 class ScCheckListMenuWindow;
@@ -103,6 +104,10 @@ class ScGridWindow : public vcl::Window, public DropTargetHelper, public DragSou
 
     std::unique_ptr<tools::Rectangle> mpAutoFillRect;
 
+    /// LibreOfficeKit needs a persistent FmFormView for tiled rendering,
+    /// otherwise the invalidations from drawinglayer do not work.
+    std::unique_ptr<FmFormView> mpLOKDrawView;
+
     struct MouseEventState;
 
     /**

sc/source/ui/view/gridwin4.cxx

@@ -1191,12 +1191,11 @@ void ScGridWindow::PaintTile( VirtualDevice& rDevice,
 
     // setup the SdrPage so that drawinglayer works correctly
     ScDrawLayer* pModel = pDoc->GetDrawLayer();
-    std::unique_ptr<FmFormView> pDrawView;
     if (pModel)
     {
-        pDrawView.reset(new FmFormView(pModel, &rDevice));
-        pDrawView->ShowSdrPage(pDrawView->GetModel()->GetPage(nTab));
-        aOutputData.SetDrawView( pDrawView.get() );
+        mpLOKDrawView.reset(new FmFormView(pModel, &rDevice));
+        mpLOKDrawView->ShowSdrPage(mpLOKDrawView->GetModel()->GetPage(nTab));
+        aOutputData.SetDrawView(mpLOKDrawView.get());
     }
 
     // draw the content