"update-preview"
signal, and call gtkFileChooserGetPreviewFilename
or
gtkFileChooserGetPreviewUri
on each change. If you can
display a preview of the new file, update your widget and
set the preview active using gtkFileChooserSetPreviewWidgetActive
.
Otherwise, set the preview inactive.gtkFileChooserSetPreviewWidget(object, preview.widget)
object
preview.widget