This signal is emitted when the preview in a file chooser should be regenerated.
For example, this can happen when the currently selected file changes. You should use this signal if you want your file chooser to have a preview widget.
Once you have installed a preview widget with set_preview_widget , you should update it when this signal is emitted. You can use the functions get_preview_filename or get_preview_uri to get the name of the file to preview. Your widget may not be able to preview all kinds of files; your callback must call set_preview_widget_active to inform the file chooser about whether the preview was generated successfully or not.
Please see the example code in Using a Preview Widget.