void gtk_file_chooser_native_set_cancel_label ( GtkFileChooserNative* self, const char* cancel_label )
Sets the custom label text for the cancel button.
If characters in
label are preceded by an underscore, they are underlined.
If you need a literal underscore character in a label, use “__” (two
underscores). The first underlined character represents a keyboard
accelerator called a mnemonic.
Pressing Alt and that key activates the button.