A display device has display panels forming a single display screen, where each display panel is connected to a display controller which receives display data of a portion of a complete image for display on the display panel. The complete image includes one or more bounded regions of display data. Each display controller receives position information relating to a change in lateral position and/or stacking order position of one or more bounded regions to be displayed at least partly on that display panel. If the display controller does not have knowledge of display data in the bounded region to be displayed on the display panel, it obtains that knowledge from another display controller. The display controller processes the display data for the portion of the complete image utilizing the knowledge obtained, and outputs the processed display data for the portion of the complete image to the corresponding display panel.