wxRect updRect = upd.GetRect();
wxRect updRectInGChars(DeviceCoordsToGraphicalChars(updRect));
// 2. for each row of chars in the update region
wxRect updRect = upd.GetRect();
wxRect updRectInGChars(DeviceCoordsToGraphicalChars(updRect));
// 2. for each row of chars in the update region