fix in panning in WPF, suggested by vdisasm
fix in panning in WPF, suggested by vdisasm

Signed-off-by: Lev Nachmanson <547e21cf4741e0be725f19d6dc4faaf8564c91d1@microsoft.com>

DebajyotiMondal/automatic-graph-layout,DebajyotiMondal/automatic-graph-layout,DebajyotiMondal/automatic-graph-layout,DebajyotiMondal/automatic-graph-layout