Display controllers and driving methods related to those in US 2013/0194250. include (a) a display controller having an update buffer, means for removing from the update buffer pixels not requiring updating, and means to ensure that pixels having certain special states are not removed from the update buffer; (b) driving a bistable display wherein, in a pixel undergoing a white-to-white transition and lying adjacent another pixel undergoing a visible transition, there is applied to the pixel balanced pulse pairs and a one top-off pulse; (c) driving a bistable display by overlaying a non-rectangular item over a pre-existing image content and then removing the item, where only pixels in the region of the item perform transitions; and (d) driving a bistable display in which background pixels not undergoing an optical change are refreshed to correct optical state drift.