gdash-countdown-clock is a simple Common Lisp + Parenscript web app presenting a countdown clock for the next meeting scheduled in my Google calendar. The calendar agenda is polled via Google's API and published to an ActiveMQ topic. See https://github.com/atgreen/gdash-gcal-poll for the trivial implementation. gdash-countdown-clock listens to that topic and pushes the "Next Meeting" time into the browser via some AJAX magic.
Background colour changes to the webapp at the T-5 and T-2 minute marks are implemented through CSS content. The colour changes are what alerts users to upcoming meetings.
I use gdash-countdown-clock as part of a personal grafana dashboard. It is presented through a grafana HTML text panel with the following content:
<style>
body {
margin: 0;
}
.parent {
display: flex;
flex-direction: column;
min-height: 100vh;
}
.parent .banner {
background: #f00;
width: 100%;
height: 30px;
}
.parent iframe {
background: #000;
border: none;
flex-grow: 1;
}
</style>
<div class="parent">
<iframe src="https://URI-FOR-MY-COUNTDOWN-CLOCK/"></iframe>
</div>
Grafana currently includes a countdown timer vizualization, but the countdown time is static, and defined in the panel definition itself. This was not sufficient for my use case -- alerting me to upcoming meetings.
This project is carrying a local version of cl-stomp, which contains a feature (heart-beat support) that is now upstream, but not currently available via quicklisp.
I hope you find this interesting and useful.
Happy hacking!
AG