OK, for posterity, here’s what I did.

I used MMM-Remote-Control and created a button element that calls a function that issues a get request. Interestingly, when I put the URL in the button code the request was rejected (no cross-origin request allowed) but when after I put the URL in the function it worked.

function toggleCal() {
            var myUrl = "http://mypi.local:8080/remote?action=TOGGLE&module=MMM-CalendarExt";
            console.log("getting " + myUrl)
            var xmlHttp = new XMLHttpRequest();
            xmlHttp.open("GET", myUrl, false); // false for synchronous request
            xmlHttp.send(null);
            return xmlHttp.responseText;
        };

The button code gets mangled here. I had to add spaces

< button onclick="toggleCal()">Calender on/off< /button>

@sdetweil Thanks for the feedback. I thought so. I guess I’ll cook something up with MMM-Remote-Control.

I have a web page with some button elements. The web page is shown via MMM-iFrameReload. How can I generate a notification from that web page? I would like to use MMM-Glance to temporarily hide another module.

Dang! Thanks. On my other screen I have that region and I didn’t replace it at all places! I owe you one.

@Sean thanks for making the effort to test it. I went the same way now. I removed everything and picked a public trash collection calendar (nice idea of yours) - still the same error. (I also commented out the showEmptyView options.)

The error appears locally (RPI3+) as well as in web browsers of all flavors.

Here’s the full config file:

var config = {
    address: "",
    port: 8080,
    ipWhitelist:
        [],
    language: "de",
    timeFormat: 24,
    units: "metric",
    modules: [
        {
            module: 'MMM-CalendarExt',
            position: "top_left", //anywhere. It is not related to real position of view
            classes: "default standard everyone",
            config: { // Read below
                system: {
                    show: ['current', 'upcoming'],
                    locale: 'de',
                    // showEmptyView: 0,
                    fullDayEventLocalize: 1,
                    redrawInterval: 300000, 

                },
                defaultView: {
                    position: 'calendar',
                    positionOrder: -1,
                    overflowRolling: 0,
                    overflowHeight: 0,
                    overflowDuration: 2,
                    timeFormat: 'H:mm',
                    dateFormat: "ddd, D. MMM",
                    fullDayEventDateFormat: "ddd, D. MMM",
                    ellipsis: 0,
                    limit: 20,
                    oneLineEvent: 1,
                },
                views: {
                    current: {
                        title: "Now...",
                        direction: "column",
                        // showEmptyView: 0,
                        useRelative: 0,
                    },
                    upcoming: {
                        title: "Upcoming...",
                        direction: "column",
                        useRelative: 0,
                        overflowHeight: 0,
                        overflowRolling: 0,
                    },
                },
                calendars: [

                    {
                        name: "Trash",
                        symbol: "male",
                        styleName: "style24",
                        url: "https://www.ekm-mittelsachsen.de/de/service-dienstleistungen/entsorgungstermine-abfallkalender/abfallkalender/ical/stadt/4870/year/2019/",
                    },
                ],
            },
        },
    ]

};

/*************** DO NOT EDIT THE LINE BELOW ***************/
if (typeof module !== "undefined") { module.exports = config; }

@Sean yes, I set it to top_left:

{
            module: 'MMM-CalendarExt',
            position: "top_left", //anywhere. It is not related to real position of view
            classes: "default standard everyone",
            config: { // Read below
                system: {
                    show: ['current', 'upcoming'],
                    locale: 'de',
                    showEmptyView: 0,
                    fullDayEventLocalize: 1,
                    redrawInterval: 300000, 
                },
                defaultView: {
                    position: 'calendar',
                    positionOrder: -1,
                    overflowRolling: 0,
                    overflowHeight: 0,
                    overflowDuration: 2,
                    timeFormat: 'H:mm',
                    dateFormat: "ddd, D. MMM",
                    fullDayEventDateFormat: "ddd, D. MMM",
                    ellipsis: 0,
                    limit: 20,
                    oneLineEvent: 1,
                },
                views: {
                    current: {
                        title: "Now...",
                        direction: "column",
                        showEmptyView: 0,
                        useRelative: 0,
                    },
                    upcoming: {
                        title: "Was steht an...",
                        direction: "column",
                        useRelative: 0,
                        overflowHeight: 0,
                        overflowRolling: 0,
                    },
                },
                calendars: [
                    {
                        name: "XXXX",
                        symbol: "male",
                        styleName: "style24",
                        url: "redacted",

                        auth: {
                            user: 'redacted',
                            pass: 'redacted',
                            method: 'basic'
                        }
                    },
                    
                ],

            },
        },

Don’t worry, it’s not urgent.

I successfully use the module on two other screens. I just set up a new one without tweaks and I run into the following error in the console (nothing gets loaded, server-side there are no errors being logged):

Uncaught (in promise) TypeError: hookDom.appendChild is not a function
    at Render.js:590
    at Array.forEach ()
    at Render.drawViews (Render.js:581)
    at Class.getDom (MMM-CalendarExt.js:209)
    at main.js:110
    at new Promise ()
    at updateDom (main.js:109)
    at Object.updateDom (main.js:518)
    at Class.updateDom (module.js:358)
    at Class.draw (MMM-CalendarExt.js:680)

@Sean Is it intentional that the z-index of the artwork (or the Spotify logo) is equal to or higher than whatever the Alert module shows? Alerts do not cover the Spotify module’s content.

Okay, I figured it out. For posterity: one needs to address the specific sub-style:

.ns-alert span.light.dimmed.medium,
.ns-alert span.thin.thin.bright.small {
    font-size: 80px !important;
}

@strawberry-3-141 I am also trying to accomplish bigger alert text. I made the suggested addition to my custom.css but it doesn’t work. What am I missing?