allow_cursored_context_menu.js

// ==UserScript==
// @name Allow cursored context menu
// @description Allow script to receive right clicks only if the right clicked element's cursor is "context-menu".
// @include http://*
// == usage ==
// set true: opera:config#UserPrefs|Allowscripttoreceiverightclicks
// ==/UserScript==

(function() {
    
    opera.addEventListener('BeforeEvent.contextmenu', function(e) {
        
        const element = e.event.target;
        const allow_context_menu = (function cursored(element) {
            
            if (!element || element.nodeType != 1) {
                return false;
            }
            
            const cursor = document.defaultView.getComputedStyle(element, '').cursor;
            if (cursor == 'context-menu') {
                return true;
            }
            
            return cursored(element.parentNode);
            
        })(element);
        
        if (!allow_context_menu) {
            e.preventDefault();
        }
        
    }, false);
    
})();