[wokwokwok]

This is a lovely write up, but oh boy... when I see:

> Finally, I proposed that the future of font shaping and drawing/ painting will involve a fully-programmable paradigm.

> Two tongue-in-cheek mis-uses of the HarfBuzz Wasm shaper appeared recently: the Bad Apple font, and llama.ttf. Check them out!

See... the thing about solving problems is that, eventually you realize that any kind of problem can be solved by simply making a platform that can execute arbitrary code.

...and you see it again and again.

Declarative compile definition in make? Why not just make it code and use cmake?

Declarative infra in terraform? Why not just make it code and use pulumi?

Declarative ui? Why not just make it code and use javascript?

Database that holds data? Why not just use stored procedures and do it in code?

The list just goes on and on, and every time you have to roll back to a few important questions:

- Is the domain so complicated you really need arbitrary code execution?

- Are you inventing a new programming language for it?

- How will people program and test for the target?

- How will you manage the security sandbox around it?

It's just such a persuasive idea; can't figure out how to deal with the complexity in configuration? Make it code and push the problem to the user instead!

Sometimes it makes sense. Sometimes it works out.

To be fair, I get it, yes, font layouts are harder than they look, and yes, using WASM as a target solves some of those issues, but I look at llama.ttf and I really have to pause and go...

...really? Does my font need to be able to implement a LLM?

I don't really think it does.

...and even if the problem is really so complex that rendering glyphs requires arbitrary code (I'm not convinced, but I can see the argument), I think you should be doing this in shaders, which already exist, already have a security sandbox and already have an ecosystem of tooling around it.

I think inventing a new programmable font thing is basically inventing a new less functional form of shaders, and it's a decision that everyone involved will come to regret...

[forrestthewoods]

I don't disagree. But I have kind of the opposite take.

I can't count how many times I've seen simple code get turned into a hideously complex declarative language that has serious gaps.

Simple UI library code? Turn it into a custom declarative syntax that is now limited!

Simple build system that works and is debuggable? Turn it into a declarative syntax that can't be debugged and can't handle all the edge cases!

And so on and so forth.

I will admit that the idea of a font programming language sounds genuinely awful to me. So I don't really disagree with your premise. But I'm increasingly annoyed with declarative system when vanilla code is often simpler, more flexible, and more powerful (by necessity). :)

[moonchild]

programmable hinting was already a thing. it's just switching to wasm from a bespoke language

[wokwokwok]

It's still just doing exactly what shaders do, which is crazy.

Explain to me exactly why, other than 'I guess someone already implemented some kind of basic version of it' that you would have to have custom CPU code rendering glyphs instead of a shader rendering SDF's like literally everyone does with shaders already?

It's not a good solution. It's a bad, easy solution.

We have a solution for running arbitrary GPU accelerated graphics instructions; it has a cross platform version with webGPU.

This font thing... looks a lot like 'not invented here' syndrome to me, as an uninvolved spectator.

Why would you chose or want not to use GPU acceleration to render your glyphs?

What 'arbitrary code' does a font need to do that couldn't be implemented in a shader?

Maybe the horse has already bolted, yes, I understand programmable fonts already exist.. but geez, its incomprehensible to me, at least from what I can see.

[vg_head]

> Explain to me exactly why, other than 'I guess someone already implemented some kind of basic version of it' that you would have to have custom CPU code rendering glyphs instead of a shader rendering SDF's like literally everyone does with shaders already?

Shaping is different compared to rendering glyphs themselves. SDF renderers (and other GPU text renderers like Slug) still do shaping on the CPU, not in shaders. Maybe some experiments have been done in this area, but I doubt anyone shapes text directly in the GPU in practice.

Think of it like a function that takes text as input, and returns positions as output. Shaders don't really know anything about text. Sure you could probably implement it if you wanted to, but why would you? I think it would add complexity for no benefit (not even performance).

[moonchild]

lengyel told me he has implemented some sort of hinting on the gpu for slug (i suspect it's not programmable, but didn't ask)

[vg_head]

Very interesting. Honestly I don't know much about hinting, but I suspect the whole shaping stack that Slug supports:

> kerning, ligature replacement, combining diacritical mark placement, and character composition. Slug also supports a number of OpenType features that include stylistic alternates, small caps, oldstyle figures, subscripts, superscripts, case-sensitive punctuation, and fractions.

Probably still uses the CPU.

[bsder]

> CPU code rendering glyphs instead of a shader rendering SDF's

1) Because SDFs suck badly (and don't cover the whole field) when you want to render sharp text. SDFs are fine when used in a game where everything is mapped to textures and is in motion at weird angles. SDFs are not fine in a static document which is rendered precisely in 2D.

2) Because GPUs handle "conditional" anything like crap. GPUs can apply a zillion computations as long as those computations apply to everything. The moment you want some of those computations to only apply to these things GPUs fall over in a heap. Every "if" statement wipes out half your throughput.

3) Because "text rendering" is multiple problems all smashed together. Text rendering is vector graphics--taking outlines and rendering them to a pixmap. Text rendering is shaping--taking text and a font and generating outlines. Text rendering is interactive--taking text and putting a selection or caret on it. None of these things parallelize well except maybe vector rendering.

[wokwokwok]

I feel like, looking at the complexity of the programs that can be implemented in shaders (eg. https://dev.epicgames.com/documentation/en-us/unreal-engine/...) that it's unreasonable, bordering on disingenuous to suggest that the GPU pipeline is not capable enough to handle those workloads, or produce pixel perfect outputs.

Be really specific.

What exactly is it that you can't do in a shader, that you can do in a CPU based sandbox, better and faster?

(There are things, sure, like IO, networking, shared memory but I'm struggling to see why you would want any of them in this context)

I'll accept the answer, 'well, maybe you want to render fonts on a toaster with no GPU'; sure... but that having a GPU isn't good enough for you, yeah... nah. I'm not buying that).

[Jasper_]

Vector graphics are really hard to do on a GPU in an efficient manner. The way the data is stored as individual curve segments makes it difficult to parallelize the coverage problem, it's equivalent to a global parse; the best approaches all do some form of parsing of curve data on the CPU, either rasterizing fully on the GPU, or putting it in a structure the GPU can chew on.

But again, this has nothing to do with HarfBuzz or wasm.

[jordo]

https://sluglibrary.com/ - game library used in many engines to do vector graphics and fonts directly on the GPU

[vg_head]

It's more about the nature of the problem, not that you can't do it in shaders. After all, I think you can do pretty much anything in shaders if you try hard enough.

Even if you already have a GPU renderer for glyphs and any other vector data, you still want to know where to actually position the glyphs. And since this is highly dependent on the text itself and your application state (that lies on the CPU), it would actually be pretty difficult to do it directly on the GPU. The shader that you would want should emit positions, but the code to do that won't be easily ported to the GPU. Working with text is not really what shaders are meant for.

[Jasper_]

It has nothing to do with shaders? Despite the name, shaping is not the same thing as a shader, shaping selects and places individual glyphs given a collection of code points.

No part of the rasterizer or renderer is configurable here. As mentioned above, the rasterizer is already programmable with up to two different bespoke stack bytecode languages, but that has nothing to do with shaping through wasm.

[slimsag]

I agree shaders would be a terrible choice for this.

However, the article clearly states there are intentions to move towards much more than just shaping in wasm:

> I proposed that the future of font shaping and drawing/ painting will involve a fully-programmable paradigm.

> Bad Apple will become much easier and faster when we introduce the draw API in Wasm.

> Drawing and painting API will eventually come to HarfBuzz, probably in 2025.

[khaled]

This is still not rasterization, but a way to modify glyph outlines on the fly. How they are rasterized eventually should be mostly unchanged.

[behdad]

Hi. As mentioned, I'll expand on my motivations in a future paper. -behdad

[adrian_b]

While this presentation is extremely interesting, it would have been far more useful if you would have exported this view into a downloadable PDF file, instead of giving access to just this ephemeral preview.

[fyrn_]

You have to shape the text even if you render the glyphs with an SDF or MSDF. You're conflating varius things

[funcDropShadow]

You are missing the point. Finally, it'll be possible to exploit side-channel attacks without using Javascript in the browser. Static HTML+CSS+Fonts websites won't be safe anymore. Yippieee! Finally, there is no reason to allow disabling Javascript anymore.

And you could add backdoors to hacked fonts that are activated by magic spells. Isn't it great.

[nineteen999]

What else are we supposed to do with all these massively multicore CPU's and gigabytes of RAM?