Slow editor scrolling

[rtfeldman]

Scrolling in the editor is much slower than expected. Watching the timeline, it appears there's an event handler in the Elm runtime that fires on scroll events, which in turn is triggering repaints.

The relevant (generated) code:

function createHandler(eventName, delegator) {
    var globalListeners = delegator.globalListeners;
    var delegatorTarget = delegator.target;

    return handler

    function handler(ev) {
        var globalHandlers = globalListeners[eventName] || []

        if (globalHandlers.length > 0) {
            var globalEvent = new ProxyEvent(ev);
            globalEvent.currentTarget = delegatorTarget;
            callListeners(globalHandlers, globalEvent)
        }

        findAndInvokeListeners(ev.target, ev, eventName)
    }
}