sw: tiled rendering, set minimal window size.

Set minimal window size (1,1), so it can trigger
LOK_CALLBACK_INVALIDATE_TILES

Change-Id: If6ef9aeec94b396febd41375b3ce96b1aa1d6115

sw/source/uibase/uno/unotxdoc.cxx

@@ -3157,12 +3157,22 @@ void SwXTextDocument::initializeForTiledRendering()
     SwViewShell* pViewShell = pDoc->getIDocumentLayoutAccess().GetCurrentViewShell();
     pViewShell->setTiledRendering(true);
 
+    if ( pViewShell->GetWin() )
+    {
+        // Check initial window size and set minimal size (1,1)
+        Size aSize( pViewShell->GetWin()->GetOutputSizePixel() );
+        if ( aSize.Width() == 0 || aSize.Height() == 0 )
+            pViewShell->GetWin()->SetOutputSizePixel(Size( std::max( aSize.Width() , long(1)),
+                                                           std::max( aSize.Height(), long(1)) ));
+    }
+
     bool      bBookMode = false;
     sal_Int16 nColumns = 1;
 
     SwView* pView = pDocShell->GetView();
     if (!pView)
         return;
+
     pView->SetViewLayout(nColumns, bBookMode, true);
 
     // Tiled rendering defaults.