eyCode == 27) { // Escape key
            hideDfnPanel({dfnPanel});
            event.stopPropagation();
            event.preventDefault();
        }
    });

    dfnPanel.dfn = dfn;
    dfn.dfnPanel = dfnPanel;
    return dfnPanel;
}



function hideAllDfnPanels() {
    // Delete the currently-active dfn panel.
    queryAll(".dfn-panel").forEach(dfnPanel=>hideDfnPanel({dfnPanel}));
}

function showDfnPanel(dfn) {
    hideAllDfnPanels(); // Only display one at a time.

    dfn.setAttribute("aria-expanded",