search.js

let objects = Class({
    get eventTarget() this,
    fooEvents: {
        popupshowing: function onPopupShowing(event) {
            mow.contextEvents.popupshowing.call(mow, event);
        }
    },
    events: {
        popupshowing: function onPopupShowing(event) {
            let menu = DOM(this.menu);
            menu.empty().append(
                template.map(iter(bookmarks.searchEngines, bookmarkcache.keywords),
                    function ([keyword, item])
                        <menuitem xmlns={XUL} xmlns:dactyl={NS}
                                  dactyl:command="search.searchSelection"
                                  label={item.title}
                                  image={item.icon}
                                  keyword={item.keyword}/>));
        }
    }
})();

overlay.overlayWindow(window, {
    objects: objects,
    after: <e4x xmlns={XUL} xmlns:dactyl={NS}>
        <menuitem id="context-searchselect" style="visibility: collapse;">
            <menu id="dactyl-context-search"
                  label="Search Selection"
                  group="selection"
                  class="menu-iconic"><menupopup key="menu" highlight="Events"/></menu>
        </menuitem>
    </e4x>.elements()
});

events.listen(document.getElementById("contentAreaContextMenu"), objects, "fooEvents");

dactyl.commands["search.searchSelection"] = function searchSelection(event) {
    let elem = DOM(event.originalTarget);
    dactyl.open(elem.attr("keyword") + " " + document.popupNode.ownerDocument.defaultView.getSelection(),
                { from: "context-search" });
};

options.get("activate")
       .values["context-search"] = "Context menu search";
options.get("newtab")
       .values["context-search"] = "Context menu search";