Debunking the belief that Dallas summers have to be survived sealed inside an air-condltfoned house, artist and home furnishings designer Mary Kehoe opens the overscale French doors to her patio, creating an outdoor living room that encourages languorous days. A few years ago, architect Frank Ryburn designed an addition, half of which was a trelllsed-topped patio, to Kehoe’s Highland Park house. Kehoe furnished the room with an easy style that makes It perfect for summer living. A generous old wooden table was planted In the comer and surrounded by pillow-strewn banquettes. Worn, but sturdy country chairs offer more seating If a dinner party grows. During the day Kehoe’s gathering table and chairs provide a base for activities away from the pool. Nothing here Is too precious for damp swimsults or wet feet. An old Kilim rug softens the brick floor beneath an ample Iron chair designed by Kehoe. One plump pillow Is a lure to enjoy a fresh glass of lemonade and a good book any time of day.