Scrawl-canvas VS yoga

I don't like Typescript because it forces me to think about types and data structures and stuff. Which is a Good Thing because I absolutely have to think about that stuff when working on large codebases with a team of colleagues: without the inline documentation and text editor help TS gives me when working on those codebases I'd be (at least!) 10x slower when refactoring old code or adding new code. And nobody wants to pay a slow developer!

However ... the one place I refuse to use Typescript is in my side project - a JS canvas library. I can justify this because: 1. it's a big codebase, but I know every line of it intimately having spent the last 10 years (re-)writing it; 2. nobody else contributes (and I kinda like it that way); and 3. I keep a close eye on competing canvas libraries and I've watched several of them go through the immense (frustrating!) work of converting their codebases to TS over the past few years and, seriously, I don't need that pain in my not-paid-for life.

Even so, I do maintain a .d.ts file for the library's 'API' (the functions devs would use when building a canvas using my library) because the testing, documentation and autocompletion help it offers is too useful to ignore. It is additional work, but it's just one file[1] and I can live with that.

[1] https://github.com/KaliedaRik/Scrawl-canvas/blob/v8/source/s...

> working with glyphs and iterating them in reverse for RTL is brain-breaking. And line wrapping gets really complicated. It's also the most obscure because nobody has written down everything you need to know in one place

I can confirm this. I've been working on a (much simpler!) text layout engine for my canvas library over the past couple of months and the amount of complexity associated with just stamping some glyphs onto a canvas has left me screaming at my laptop on an almost daily basis. Getting a decent underline was a proud moment!

Question: did you ever find out what algorithm the various browsers are using to calculate how many words can fit on a given line? I'm almost there, except words will occasionally jump between lines when I scale the text. Really annoying!

The PR's still a work in progress, but I've got all the functionality I want in there (shaping lines to fit in non-rectangular containers, styling text, text along a non-straight line, dynamic updates, etc). Just need to test and document it all now ... https://github.com/KaliedaRik/Scrawl-canvas/pull/75

I've got myself organised and prepared a List Of Things To Do[1] to make my 2D Javascript library even better than it already is. Given that I've been working on the library for over 10 years now, and have never before set out such a list, I call this Progress!

[1] https://github.com/KaliedaRik/Scrawl-canvas/discussions/cate...

'Kay, I don't know if this anywhere close to what the OP wants, but this sort of live browser tab manipulation is possible to do using a mix of a a canvas element and the browser's Screen Capture API[1] (plus my JS canvas library, once I merge and publish the changes into its next release[2]).

This solution[3] shows the modified browser tab in a separate browser tab. I've got no idea whether it's possible to do the same sort of trick in the same tab (but probably not). I also have no idea how secure the Screen Capture API is - I'd get very nervous about doing this sort of thing when looking at my bank's online portal!

[1] https://developer.mozilla.org/en-US/docs/Web/API/Screen_Capt...

[2] https://github.com/KaliedaRik/Scrawl-canvas/pull/57

[3] Youtube video of the effect: https://www.youtube.com/watch?v=hCi6LmKMAo0

My canvas library's README[1] has a video embedded in it. FWIW I'm not convinced it adds anything to the library's sales pitch.

[1] https://github.com/KaliedaRik/Scrawl-canvas

> And I’m just mentioning some of the unfixable problems with this approach

I agree that using a canvas instead of leveraging existing accessibility supplied by HTML/CSS/JS and the DOM is an accessibility nightmare.

However, I disagree that canvas accessibility issues are "unfixable". Difficult? Yes. But not unfixable. In my view, the element works best in partnership with its wider environment (HTML/CSS/JS and the DOM), not as a replacement for it. With that in mind, we can start to tackle the accessibility issues you raise - fonts, links, interactions, etc.[1][2]

I have an ambition to one day become intelligent enough to understand/code in Rust, and I'm really glad to see that people are thinking about accessibility as a fundamental part of UIs being developed in Rust.

[1] - Which is what my JS 2d canvas library tries to do: https://scrawl-v8.rikweb.org.uk/

[2] - My thoughts on accessibility, and how I try to fix them using my library: https://scrawl-v8.rikweb.org.uk/learn/eleventh-lesson/

If, however, your company is set on this course, I very strongly suggest you use a canvas library - if only for the MVP. Here's my canvas library (spam alert!) ... even if you don't use it in your product, the library might help give you some ideas on how to overcome some of the responsive, interactive and accessibility issues you'll be facing.

Scrawl-canvas - example and another example (links to code at bottom of each page)

We still wanted to leverage a layout engine that could be performant and easy-to-use. After doing some performance testing with native UIKit, Autolayout, and a few other third-party options, we ended up bringing FlexLayout into the mix, which is a Swift implementation of Facebook’s Yoga layout engine. All RPL components utilize FlexLayout in order to lay out content fast and efficiently. While we’ve enjoyed using it, we’ve found a few touch points to be mindful of. There are some rough edges we’ve found, such as utilizing stack views with subviews that use FlexLayout, that often come at odds with both UIKit and FlexLayout’s layout engines.

We have our own test suite (orginally derived from the test suite of Meta's Yoga layout library [0]) which consists of text fixtures that are small HTML snippets [1] and a test harness [2] that turns those into runnable tests, utilising headless chrome both to parse the HTML and to generate the assertions based on the layout that Chrome renders (so we are effectively comparing our implementation against Chrome). We currently have 686 generated tests (covering both Flexbox and CSS Grid).

We would like to utilise the Web Platform Test suite [3], however these are not in a standard format and many of the tests require JavaScript so we are not currently able to do that.

[0]: https://github.com/facebook/yoga

[1]: https://github.com/DioxusLabs/taffy/tree/main/test_fixtures

[2]: https://github.com/DioxusLabs/taffy/tree/main/scripts/gentes...

[3]: https://github.com/web-platform-tests/wpt/tree/master/css/cs...

The "engine" is built on top of amazing https://www.lwjgl.org/ and https://github.com/bkaradzic/bgfx/, and UI system is baked by https://github.com/memononen/nanovg and https://github.com/facebook/yoga

React Native uses the Yoga engine under the hood, which allows you to use CSS properties to layout your React Native UI in a way that translates really well. Layout in Yoga is limited to Flexbox and absolute/relative positioning, however; there is no CSS grid and no display attribute. This keeps things simpler and more performant, but if developers are accustomed to using other layout techniques on the web, they’ll need to adjust to this new limitation.

PR #246 is super interesting to check out: by fixing the caching strategy, we were able to eliminate an exponential time (with respect to tree depth) performance penalty, and get comparable speeds for flat and deeply nested layouts (something I'd never expected to be possible). Preliminary benchmarks shows us significantly faster than yoga, Meta's C++ library for the same thing, especially on deep trees. Not too shabby for a tiny team of volunteers!

You're going to build the CLI using Ink, a React component-based library for building interactive CLIs. It uses Yoga to build Flexbox layouts in the terminal, so most CSS-like props are available in Ink as well. Ink is simply a React renderer for the terminal, so all the React features are supported. No need to learn a new syntax specific to Ink.

Interesting.

I was thinking that this was going to be a crazy amount of layout engine work, but now I look a little closer it appears the layout work is farmed out to yoga [0] (not trying to take away anything from the effort here). So this project is almost a wrapper around running yoga as a renderer and using SVG as a form of backend target?

I say "appears" because the yoga landing page doesn't do a great job of explaining what it does.

[0] https://github.com/facebook/yoga