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 update-preview
signal, and call gtk_file_chooser_get_preview_filename() or
gtk_file_chooser_get_preview_uri() 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_set_preview_widget_active().
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.
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 update-preview signal, and call gtk_file_chooser_get_preview_filename() or gtk_file_chooser_get_preview_uri() 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_set_preview_widget_active(). 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.