tdf#111785 Save hatch background color in pptx format.

When exporting to pptx from LO, the background color of
the hatching is preserved. The default background, when no
hatch background is set is transparent.

Change-Id: Ie44c89a9ce54eef49100b3e7b376c27c1a952fcf
Reviewed-on: https://gerrit.libreoffice.org/46098Reviewed-by: Tamás Zolnai <tamas.zolnai@collabora.com>
Tested-by: Tamás Zolnai <tamas.zolnai@collabora.com>

oox/source/export/drawingml.cxx

@@ -1189,9 +1189,26 @@ void DrawingML::WritePattFill( const Reference< XPropertySet >& rXPropSet )
         WriteColor(aHatch.Color);
         mpFS->endElementNS( XML_a , XML_fgClr );
 
-        // In Writer hatching has no background so use white as a default value.
+        sal_uInt32 nColor = COL_WHITE;
+        sal_Int32 nAlpha  = 0;
+        bool isBackgroundFilled = false;
+
+        if ( GetProperty( rXPropSet, "FillBackground" ) )
+        {
+            mAny >>= isBackgroundFilled;
+            if( isBackgroundFilled )
+            {
+                nAlpha = MAX_PERCENT;
+
+                if( GetProperty( rXPropSet, "FillColor" ) )
+                {
+                    mAny >>= nColor;
+                }
+            }
+        }
+
         mpFS->startElementNS( XML_a , XML_bgClr, FSEND );
-        WriteColor(COL_WHITE);
+        WriteColor(nColor, nAlpha);
         mpFS->endElementNS( XML_a , XML_bgClr );
 
         mpFS->endElementNS( XML_a , XML_pattFill );