Hacker News Reader

Comment by stefan_ | Hacker News Reader

I don't understand, WASM can't use canvas?

Because if you "blit a bunch of pixels to the screen", you don't care about performance regardless.

A complex browser API like canvas requires much more effort to "emulate" in WASI than a simple 2D framebuffer access. I think emulating the Linux framebuffer device is the right first step.

PS: I think there's some confusion about WASM running in browsers, vs WASM running on top of WASI. WASI is all about running WASM outside the browser: https://wasi.dev/

The Linux framebuffer device is a legacy thing which doesn't mesh with the way modern graphics chipsets work. GPUs today are practically glorified sprites engines where a "framebuffer", a "texture" and a "sprite" are essentially one and the same in implementation, and new entities can be created by compositing ("blitting") existing ones with arbitrary 3D transformations, alpha-blending, anti-aliasing etc. You don't want to be limited to a single frame-buffer with pixel-level access and everything being drawn/blitted by software, that would be dog-slow.

It's not about performance but about convenience. Having a way to plot single pixels with the CPU without a lot of boilerplate code to setup a 3D API context, creating textures, vertex buffers, shaders etc etc is a good thing to have in many situations.

That this is not a good way for doing more complex rendering tasks seems quite obvious (e.g. in the long run this cannot be the only API for covering all sorts of rendering, but it happens to be a good sweet spot for getting anything on screen at all, and not having to deal with an overly complex rendering API just to get some 2D image data rendered).

If convenience is what you want, that can be provided by a 2D canvas. This could even support a "soft framebuffer", i.e, a pixel-perfect canvas taking up the full screen, or some well-defined window inside it. But that would not be a low-level rendering API, of course.

gpu.js has this in a really (in js terms) performant way. I love that project.

In almost no situations you want to have software, pixel-based access.

Are we really going back 30 years?

To reinforce on this: is pixel actually a well defined usable unit? as far as I understood many modern monitor often use a definition of pixel quite different from the one of a couple decades ago.

Pretty much the only popular abstraction I’m aware of that most GPUs share (as far as complex graphics operations go) is shader programs. That’s a pretty complex abstraction compared to a framebuffer which is quite frankly good enough for most things.

Reply on news.ycombinator.com