cairo:push-group-with-content (cr content)

cr -- a cairo:context-t instance
content -- a cairo:content-t value indicating the type of group that will be created

Temporarily redirects drawing to an intermediate surface known as a group. The redirection lasts until the group is completed by a call to the cairo:pop-group or cairo:pop-group-to-source function. These calls provide the result of any drawing to the group as a pattern, either as an explicit object, or set as the source pattern.

The ability to control the content type is the only distinction between this function and the cairo:push-group function which you should see for a more detailed description of group rendering.