Passes an activate event to the cell renderer for possible processing.
Some cell renderers may use events; for example, `GtkCellRendererToggle` toggles when it gets a mouse click.
widget that received the event
widget-dependent string representation of the event location; e.g. for `GtkTreeView`, a string representation of `GtkTreePath`
background area as passed to
cell area as passed to
true if the event was consumed/handled