A file-filter can be used to restrict the files being shown in a file-chooser. Files can be filtered based on their name (with gtk_file_filter_add_pattern()), on their mime type (with gtk_file_filter_add_mime_type()), or by a custom filter function (with gtk_file_filter_add_custom()).
Filtering by mime types handles aliasing and subclassing of mime types; e.g. a filter for text/plain also matches a file with mime type application/rtf, since application/rtf is a subclass of text/plain. Note that GtkFileFilter allows wildcards for the subtype of a mime type, so you can e.g. filter for image/*.
Normally, filters are used by adding them to a GtkFileChooser, see gtk_file_chooser_add_filter(), but it is also possible to manually use a filter on a file with gtk_file_filter_filter(). Slots: