pushBlend
Blends together two images with the given blend mode.
Until the first call to method@Gtk.Snapshot.pop, the bottom image for the blend operation will be recorded. After that call, the top image to be blended will be recorded until the second call to method@Gtk.Snapshot.pop.
Calling this function requires two subsequent calls to method@Gtk.Snapshot.pop.
Parameters
blendMode
blend mode to use