FileChooser.setPreviewWidget

Sets an application-supplied widget to use to display a custom preview of the currently selected file. To implement a preview, after setting the preview widget, you connect to the #GtkFileChooser::update-preview signal, and call [gtk.file_chooser.FileChooser.getPreviewFilename] or [gtk.file_chooser.FileChooser.getPreviewUri] on each change. If you can display a preview of the new file, update your widget and set the preview active using [gtk.file_chooser.FileChooser.setPreviewWidgetActive]. Otherwise, set the preview inactive.

When there is no application-supplied preview widget, or the application-supplied preview widget is not active, the file chooser will display no preview at all.