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
may display an internally generated preview of the current file or
it may display no preview at all.
Since 2.4
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 may display an internally generated preview of the current file or it may display no preview at all. Since 2.4