| > Google has proposed a placeElement method that allows you to render HTML and CSS into a canvas I've just read it. Oh, dear ... what an awful proposal! My initial thoughts, reacting to the README at https://github.com/WICG/canvas-place-element > There’s a strong need for better text support on Canvas. [...] This includes not only visual features but also the possibility of supporting the same level of user interaction as the rest of the web Agreed, but ... adding HTML/CSS to a raster (or WebGL etc) image is not the way to do it. I much prefer your idea of incorporating HarfBuzz-like functionality into the canvas/text APIs - especially given that HarfBuzz is included as part of most browsers' code base. I've played with mixing HTML/CSS with canvas in my canvas library. The results are ... interesting[1][4], but (probably) not the ideal solution. Making it easy for developers to build canvas interactions with HTML/events anywhere on the page is much more productive and useful[2]. > There is currently no guarantee that the canvas fallback content currently used for accessibility always matches the rendered content, and such fallback content can be hard to generate. My thinking is that directly reflecting the canvas text back into the DOM is often not useful for people using screen readers. They don't need to hear every number on the chart axis when instead they could be presented with just the measure and range of the axis. If the HTML element rapidly/repeatedly updates its content, it's going to be a very unpleasant experience for the user. I've experimented with this sort of thing in [2], but need feedback from real screenreader users to understand if the solution meets their needs. > Access to live interactive forms, links, editable content with the same quality as the web. This will help to close the app gap with Flash. Flash is dead. Please leave its bones in the crypt. > 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 I only work with 2D canvas, but I can understand the desire here. A different approach might be to convince browser devs to work on improving SVG (and CSS) filters to support WebGL shaders, which can then be used by the canvas? Though Safari still doesn't support using SVG filters in the canvas so maybe convince them first? Playing with filter effects is one of the joys I get from working on my canvas library[3] - but that's got nothing to do with text layout ... except when applying the filter to text, of course![4] [1] - Use stacked DOM artefact corners as pivot points https://scrawl-v8.rikweb.org.uk/demo/dom-015.html [2] - London crime charts https://scrawl-v8.rikweb.org.uk/demo/modules-001.html [3] - A gallery of compound filter effects https://scrawl-v8.rikweb.org.uk/demo/filters-103.html [4] - Editable header text colorizer and animation effect snippets https://scrawl-v8.rikweb.org.uk/demo/snippets-006.html |
I've taken a similar approach to layering canvases with normal HTML (typically the HTML is on top). I don't have a problem logically representing what's painted on the canvas and doing my own hit detection either. Shaders and text shaping in canvas sound a lot more attractive to me than placeElement, but I guess we'll see. I should get around to campaigning for ctx.shapeText and ctx.fillGlyphs but I don't know how much folks care about it.