void gtk_text_buffer_set_modified (GtkTextBuffer *self, gboolean setting);
Used to keep track of whether the buffer has been modified since the last time it was saved. Whenever the buffer is saved to disk, call gtk_text_buffer_set_modified (@buffer, FALSE). When the buffer is modified, it will automatically toggled on the modified bit again. When the modified bit flips, the buffer emits a "modified-changed" signal.