Gtk.TextIter.prototype.can_insert

function can_insert(default_editability:Boolean):Boolean {
    // Gjs wrapper for gtk_text_iter_can_insert()
}

Considering the default editability of the buffer, and tags that affect editability, determines whether text inserted at iter would be editable. If text inserted at iter would be editable then the user should be allowed to insert text at iter. Gtk.TextBuffer.prototype.insert_interactive uses this function to decide whether insertions are allowed at a given position.