An apparatus comprises an electrowetting display device comprising: a first support plate including: a surface; and a first electrode. The apparatus further comprises a second support plate and a protrusion having a protrusion surface. The protrusion is formed as part of at least one of the first support plate or the second support plate. The protrusion has an elongate shape extending from one to the other of the first or second support plates. At least one memory and computer program instructions are configured to, with at least one processor, control a volume of the first fluid adjoining the protrusion surface and a volume of the first fluid adjoining the surface of the first support plate, by controlling a magnitude of a first voltage applied between the first and second electrodes, and by controlling a magnitude of a second voltage applied between the third and second electrodes.