selection -- a gtk:tree-selection object
mode -- a gtk:tree-model object being viewed
path -- a gtk:tree-path instance of the row in question
selected -- true, if the path is currently selected
result -- true, if the selection state of the row can be toggled

A callback function used by the gtk:tree-selection-set-select-function function to filter whether or not a row may be selected. It is called whenever the selection state of a row might change. A return value of true indicates to selection that it is okay to change the selection.