public void set_fixed_height_from_font (int number_of_rows)
Sets the height of a renderer to explicitly be determined by the “font” and “y_pad” property set on it.
Further changes in these properties do not affect the height, so they must be accompanied by a subsequent call to this function. Using this
function is inflexible, and should really only be used if calculating the size of a cell is too slow (ie, a massive number of cells displayed).
number_of_rows is -1, then the fixed height is unset, and the height is determined by the properties again.
Number of rows of text each cell renderer is allocated, or -1