The Oakland-based supermarket company said its board of directors declared a dividend distribution, to be made Feb. 24, of one common stock purchase on each outstanding share of common. Each right will entitle shareholders to buy a newly issued share at a price of $100. The rights will be exercisable only if a person or group buys 20% or more of the common stock or announces a tender offer that could result in ownership of 30% or more of the stock. The rights will be redeemable by Safeway at 5 cents per right at any time before a 20% position has been acquired. The company said it is not aware of any effort to acquire control of the firm.