A method comprising: associating a first graphic context with a first application; associating a second graphic context with a second application; attaching the first graphics context to a first window, to direct to the first window graphics resulting from operation of the first application; attaching the second graphics context to a second window, to direct to the second window graphics resulting from operation of the second application; detaching the first graphics context from the first window; detaching the second graphics context from the second window; attaching the second graphics context to the first window; attaching the first graphics context to the second window; characterized by the steps of: assigning a first identifier to a first display layer, the first window associated with the first layer; assigning a second identifier to a second display layer, the second window associated with the second layer; filling memory locations of a buffer with the first identifier, the memory locations filled with the first identifier corresponding to a display region of the first window which, in turn, corresponds to screen pixels; and filling memory locations of the buffer with the second identifier, the memory locations filled with the second identifier corresponding to a display region of the second window overlapping said display region of the first window at the same screen pixels, whereby said buffer has a plurality of memory locations for each screen pixel. associating a first graphic context with a first application; associating a second graphic context with a second application; attaching the first graphics context to a first window, to direct to the first window graphics resulting from operation of the first application; attaching the second graphics context to a second window, to direct to the second window graphics resulting from operation of the second application; detaching the first graphics context from the first window; detaching the second graphics context from the second window; attaching the second graphics context to the first window; attaching the first graphics context to the second window; characterized by the steps of: assigning a first identifier to a first display layer, the first window associated with the first layer; assigning a second identifier to a second display layer, the second window associated with the second layer; filling memory locations of a buffer with the first identifier, the memory locations filled with the first identifier corresponding to a display region of the first window which, in turn, corresponds to screen pixels; and filling memory locations of the buffer with the second identifier, the memory locations filled with the second identifier corresponding to a display region of the second window overlapping said display region of the first window at the same screen pixels, whereby said buffer has a plurality of memory locations for each screen pixel. assigning a first identifier to a first display layer, the first window associated with the first layer; assigning a second identifier to a second display layer, the second window associated with the second layer; filling memory locations of a buffer with the first identifier, the memory locations filled with the first identifier corresponding to a display region of the first window which, in turn, corresponds to screen pixels; and filling memory locations of the buffer with the second identifier, the memory locations filled with the second identifier corresponding to a display region of the second window overlapping said display region of the first window at the same screen pixels, whereby said buffer has a plurality of memory locations for each screen pixel.