column -- a gtk:tree-view-column object
renderer -- a gtk:cell-renderer object that is being rendered by the tree view column
model -- a gtk:tree-model object being rendered
iter -- a gtk:tree-iter object of the current row rendered

A function to set the properties of a cell instead of just using the straight mapping between the cell and the model. This is useful for customizing the cell renderer. For example, a function might get an integer from the tree model, and render it to the "text" attribute of the cell by converting it to its written equivalent. This is set by calling the gtk:tree-view-column-set-cell-data-func function.