package Ġcom . simple mobile tools . draw . interfaces Ċ Ċ interface ĠCanvas Listener Ġ{ ĊĠĠĠ Ġfun Ġtoggle Undo Visibility ( visible : ĠBoolean ) ĊĊĠĠĠ Ġfun Ġtoggle Redo Visibility ( visible : ĠBoolean ) Ċ } Ċ