Earlier quoted context omitted.
Performance of DOM based rendering is very problematic and not unified across browser implementations. Canvas rendering will likely increase the performance of Google Docs, and make the UX more unified across platforms. Google Docs is really an application built on the web platform. HTML DOM rendering was never intended to give developers the control they need to build fully featured high performant applications, we…
I think this is the real reason for the change as well. A few years ago Visual Studio Code underwent a similar change where rendering the terminal moved from using DOM to canvas. I never noticed a huge difference between the two methods but I imagine using canvas gave them a lot more flexibility in addition to being more performant.
I'm perplexed because I don't expect canvas rendering to be faster - or necessarily more flexible - because the web is document-first: HTML and CSS were/are all built-around describing and styling textual content, and computer program source code files are invariably all textual content files. So while browsers all have heavily-optimized fast-paths written in native code for rendering the DOM to the screen with the full flexibility of all of CSS's styling features - so applications switching to canvas rendering will first have to contend with needing to reimplement at least the subset of CSS that they're using for their editor - and it has to run as JavaScript (or WASM?) - and I just don't understand how that could possibly be faster than letting the DOM do its thing.
I appreciate that DOM+CSS rendering is not designed-around monospaced text editing or with specific support for typical text-editor and IDE features which do indeed throw a wrench into the works[1], but I think a much better approach would be to carve-out the cases where the current DOM and rendering model is insufficient or inappropriate for those specific applications' purposes and find a way to solve those problems without resorting to canvas rendering.
That said, is this change because Google wants to use Flutter for a single codebase for Google Docs that would work across iOS, Android, and the web? Flutter does have a HTML+DOM+CSS rendering mode, but it's horrible (literally thousands of empty elements in their hello-world example...)
[1] e.g. a HTML/DOM document is strictly an unidirectional acyclic tree structure, and CSS selectors are also strictly forwards-only (e.g. you cannot have a HTML element that spans other elements, you cannot isolate individual text characters, you cannot select a descendant element to style based on its subsequent siblings, or ancestor's subsequent siblings), and how the render-state of a document is also strictly derived from the DOM and so does not allow for any feedback loops unless you start to use scripts, which means you can't select elements to style based on their computed styles (unlike, for example, WPF+XAML, where you can bind any property to another property - something I think XAML implements horribly...), and I appreciate this makes certain kinds of UI/UX work difficult (if not impossible in some cases), but in the use-case of an editor I just don't see these as being show-stopper issues.