by rikroots | 2025-08-03 09:23:56+00:00
Please excuse me for spamming this thread with examples of how my canvas library approaches these issues:

> Use case: Styled, Laid Out Content in Canvas. There’s a strong need for better styled text support in Canvas. Examples include chart components (legend, axes, etc.), rich content boxes in creative tools, and in-game menus.

Single line, unstyled text is relatively easy using the Canvas API. Multiline text is a world-of-pain. Styled text is a completely separate world-of-pain. Underlined text? Same! So that's gives us a problem space of world-of-pain-cubed. Don't talk to me about RTL text, vertical text, CJK punctuation, Thai text ignoring spaces as a word separator, heavily kerned fonts (staring at you, Arabic and Devangari), etc.

Demo: https://scrawl-v8.rikweb.org.uk/demo/canvas-207.html

This demo takes the following html markup and displays it in a truncated circle shape. The styling itself happens in CSS - see here: https://github.com/KaliedaRik/Scrawl-canvas/blob/v8/demo/can...

const westernText = '<span class="underline">Lorem</span> ipsum <b>dolor sit</b> amet, con&shy;sectetur adi&shy;piscing &eacute;lit, sed 
do eius-mod
 <u>tempoj yn&shy;figizqunt</u> ut <span class="stamp-outlined">labore et dolore</span> <span class="green-highlight">magna aliqua.</span> Ut enim ad <span class="bold">minim veniam,</span> quis <span class="letter-spaced">nostrud</span> exercit-ation <span class="strike">ullamco laboris</span> nisi ut aliquip ex ea <span class="make-monospace">"commodo"</span> consequat. Duis <em>(aute irure d&ouml;lor)</em> in reprehenderit &icirc;n <i>voluptate</i> velit &copy;2024 <i>esse &lt;cillum&gt; <b>dolore</b> eu fugiat nulla</i> pariatur. <span class="red">Excepteur sint</span> occaecat &iexcl;cupidatat! <strong>non proident,</strong> <span class="word-spaced">sunt in culpa qui</span> offici&thorn;a deserunt <span class="make-bigger"><span class="green-highlight">mollit</span> anim</span> id est laborum.';

As for the other things I don't want to talk about, see this other demo which attempts to overcome those issues: https://scrawl-v8.rikweb.org.uk/demo/canvas-206.html

> Use case: Accessibility Improvements. There is currently no guarantee that the canvas fallback content currently used for <canvas> accessibility always matches the rendered content, and such fallback content can be hard to generate. With this API, elements drawn into the canvas bitmap will match their corresponding canvas fallback.

I welcome and applaud this focus on making canvas text accessible. However it's not enough (in my highly opinionated opinion) to just reflect the text back into the DOM. People using screen readers probably don't need every number on the Y axis read out to them every time they navigate onto a chart, they probably just need to hear values as they keyboard navigate the chart.

Demo: https://scrawl-v8.rikweb.org.uk/demo/modules-001.html

The canvas element is highly inaccessible - I've tried to detail all the issues that have to be addressed here (again, a highly opinionated take): https://scrawl-v8.rikweb.org.uk/docs/reference/sc-accessibil...

> Use case: Composing HTML Elements with Shaders. A limited set of CSS shaders, such as filter effects, are already available, but there is a desire to use general WebGL shaders with HTML.

We already have a comprehensive set of filter effects available through SVG <filter> elements. They are, however, difficult to compose and have a tendancy to be computationally heavy. WebGL shaders can be fantastic, but face the (current) limit of how many WebGL canvas elements you can include on a page; they're also difficult to compose.

For my library's filter engine, I took inspiration from the SVG approach. Details can be found here: https://scrawl-v8.rikweb.org.uk/docs/reference/sc-filter-eng...

> Use case: HTML Rendering in a 3D Context. 3D aspects of sites and games need to render rich 2D content into surfaces within a 3D scene.

HTML canvas elements are just DOM elements, and can be 3d-rotated like other elements. Interacting with 3d-rotated canvas elements is an interesting problem space.

Classic rotating cube demo: https://scrawl-v8.rikweb.org.uk/demo/dom-008.html

Tracking the mouse over a 3d-rotated canvas element demo: https://scrawl-v8.rikweb.org.uk/demo/dom-013.html