adnauseum

This morning I was configuring an app and it gave me three options for cursor styles: box, underscore and vertical bar.

The vertical bar has always made sense with me—it lives in-between letters, for example: when I see "test|ing" I know that my cursor is in-between the final "t," but before "i." If I type "X" I'll get: "testXing."

By contrast, in this app the box cursor is like this: "test[i]ng" and if I type "X," it's not obvious to me that I'll get "testXing" instead of "testiXng."

I get that this is a matter of preference, but I'm curious to know why underscore and box would be preferable to vertical bar.

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Here's images of the same cursor placement, but different styles:

- Example of vertical bar: https://user-images.githubusercontent.com/24446573/156610316-47df7923-744a-4b14-a23a-ddbac873ba59.png

- Example of underscore: https://user-images.githubusercontent.com/24446573/156610217-120f96f8-2f82-4577-8a02-67458d663841.png

- Example of box: https://user-images.githubusercontent.com/24446573/156609948-4f814ef6-9a30-4cfe-9db7-1ddbe75ec051.png

Every week at work I get a bunch of reminders which I schedule in apps like Slack, Google Calendar, etc. These notifications arrive always within the minute that I scheduled and it always impresses me! Delightful!

I want to learn about how a this type of system is designed. I've searched a lot, but haven't yielded anything about systems that handle scheduled notifications.

Some wonderings: - What is the name given to these types of systems (if any)? - How does one design a system like this? - Are there any open source projects I can learn from?

My work uses Google Calendar. I'm amazed that I always get notifications for meetings on time and in multiple mediums (i.e., email, push notification, etc).

How is a notification system like this built? I've been poking around for time-based event systems, but I don't think that's the right thing to look at.

Finally, how can you scale this? I'm just imagining a ton of distributed cron-y things, but I know that's naive.