browser-zoom-listener & simple-resize-observer

Did I just do three days worth of work for no reason?

I solved a problem that didn't exist. Instead of walking away from this in shame, I'm going to reflect on it so I feel like my time was at least marginally worthwhile.

Introducing:

• browser-zoom-listener referred to as BZL
• simple-resize-observer referred to as SRO

I read a StackOverflow answer that talked about the issues of too many events being sent. I saw that the author used window.requestAnimationFrame and a dirty flag to debounce excess events so that the callback wasn't called more than it needed to be. I thought it was so clever that I decided to make BZL. BZL was more of a fight against TypeScript and it's exports. I learned a whole lot about the type system so it wasn't entirely pointless. So I finished BZL and published it... a few times because I screwed up. It was some of the best code I had done in a hot minute and I was pleased.

SRO was basically a clone of BZL except it was for the ResizeObserver. I hear someone saying that I should have made an abstraction over the two but

"I've made enough bad code choices to know when to stop abstracting." (and other jokes I tell myself)

I polished up the demo. It even had HLJS! I figured that I'd add a callback counter display for good measure. And yet again, I had forgotten to set the dirty flag. So I set the dirty flag and didn't notice a difference. I was wondering if my code wasn't debouncing correctly. After like two minutes of print debugging, the only conclusion that I could come to was that the animation frames were dispatching events faster than I could trip the debouncing mechanism.

https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserver

ResizeObserver avoids infinite callback loops and cyclic dependencies that are often created when resizing via a callback function. It does this by only processing elements deeper in the DOM in subsequent frames. Implementations should, if they follow the specification, invoke resize events before paint and after layout.

Aaaaand the ResizeObserver invokes events only before paint. Nice one! I solved a problem that didn't exist.

Slightly worried, I went to check BZL. Surely the resize event on Window would be fired every time the inspect element pane was resized too, right? No. First of all, that's the document that's being resized. Not the Window. Ok well, what happens when we resize the Window? Well, you get a lot of events but debouncing them isn't even an issue since all we're looking for is a change in zoom, AKA window.devicePixelRatio.

So what have I learned?

• Check if something is a problem before trying to solve it
• A cool way to debounce events using window.requestAnimationFrame
• TypeScript exports and .d.ts files
• This cursed /// <reference types="path"/> .d.ts import directive
• Rollup's rollup.config.cjs
• A few fields in the package.json

BZL and SRO are still useful, though. Just not enough to be their own modules. I'll stick some TypeScript files in this repo that anyone (probably just me) can just grab and use.