Show HN: Tetris in a PDF • Hacker News Board

Re: Show HN: Tetris in a PDF

#21

Post by btown » Thu, Jan 09, 2025, 4:21 PM UTC

I, for one, was surprised that Chrome's PDF renderer would allow persistent JS code like this to run - not just limited code in response to user actions, but a real game loop.

But there's a spec for all this and everything! https://www.t10.org/ftp/js_api_reference.pdf (2007) - be warned, the light of Ecma TC39 standardization does not extend to this place.

Chromium's implementation of setInterval for instance (which, in this world, takes a string to evaluate): https://pdfium.googlesource.com/pdfium/+/refs/heads/main/fxj... -> https://pdfium.googlesource.com/pdfium/+/refs/heads/main/fxj...

From a security perspective, they're able to build on top of V8 isolate primitives and Chrome's sandboxing systems - but from the logs, security improvements in PDFium are being continuously developed as recently as the past few weeks! I feel like I've stumbled upon a parallel universe, in the best possible way.

Re: Show HN: Tetris in a PDF

#22

Post by internetter » Thu, Jan 09, 2025, 4:27 PM UTC

Atari Breakout for PDF: https://cdn.jsdelivr.net/gh/osnr/horrifying-pdf-experiments@...

Re: Show HN: Tetris in a PDF

#23

Post by mati365 » Thu, Jan 09, 2025, 4:29 PM UTC

So it's possible to port C compiler to PDF. Compiler is already done https://github.com/Mati365/ts-c-compiler. We can run DOS in PDF basically..

Re: Show HN: Tetris in a PDF

#24

Post by ThomasRinsma » Thu, Jan 09, 2025, 4:31 PM UTC

weinzierl wrote: post #19

"It was a bit tricky to find a union of features that work in both engines [..]" I am curious what the constraints are to make this work and in which environments it does? Does it work in PDF viewers outside the browser? Is there documentation what is available in which environment? What is enabled by default, can be switched on or off?

I barely looked at Adobe Reader so not sure about that one, it definitely does not work with this PDF though, likely because it's not compliant in several ways. Besides that I wouldn't be surprised if it supports all the required JS APIs and more, just possibly behind some permission prompts.

It might work in Foxit as I believe it supports some scripting. Most of the other native PDF renderers are more static, as far as I know. In either case, I was most interested in the browser-native engines, as I always thought of them as more "static"/limited.

As for documentation on specific features: to be honest, I just looked at the implementations of PDF.js and PDFium. Both only support a subset of the "standard" API, likely for security reasons. But PDF.js for example allows changing a field's background color (colored pixels!), and PDFium allows modifying their position/bounding box (I tried a high res color display by moving a row vertically as if it's a scanline, but things become quite laggy).

Re: Show HN: Tetris in a PDF

#25

Post by bowmessage » Thu, Jan 09, 2025, 4:32 PM UTC

mati365 wrote: post #23

So it's possible to port C compiler to PDF. Compiler is already done https://github.com/Mati365/ts-c-compiler . We can run DOS in PDF basically..

Adobe Acrobat DOOM Pro™

Re: Show HN: Tetris in a PDF

#26

Post by anothername12 » Thu, Jan 09, 2025, 4:37 PM UTC

frizlab wrote: post #6

Fortunately this does not work in Safari where the rendering is done natively.

Does not even seem to be a valid PDF according to Preview.app

Re: Show HN: Tetris in a PDF

#27

Post by mati365 » Thu, Jan 09, 2025, 4:43 PM UTC

bowmessage wrote: post #25

mati365 wrote: post #23

So it's possible to port C compiler to PDF. Compiler is already done https://github.com/Mati365/ts-c-compiler . We can run DOS in PDF basically..

Adobe Acrobat DOOM Pro™

What about running Adobe Acrobat in Adobe Acrobat?

Re: Show HN: Tetris in a PDF

#28

Post by GaggiX » Thu, Jan 09, 2025, 4:46 PM UTC

Kinda happy that Evince doesn't start executing JS when opening a PDF.

Re: Show HN: Tetris in a PDF

#29

Post by andrea76 » Thu, Jan 09, 2025, 4:48 PM UTC

mati365 wrote: post #27

bowmessage wrote: post #25

Earlier quoted context omitted.

Adobe Acrobat DOOM Pro™

What about running Adobe Acrobat in Adobe Acrobat?

Can we run Windows 3.1 in protected mode from a PDF?

Re: Show HN: Tetris in a PDF

#30

Post by lxgr » Thu, Jan 09, 2025, 4:48 PM UTC

mati365 wrote: post #23

So it's possible to port C compiler to PDF. Compiler is already done https://github.com/Mati365/ts-c-compiler . We can run DOS in PDF basically..

That's how it inevitably goes with Turing completeness :)

The real achievement here arguably isn't running code (that's provided by the PDF spec and implementations), but managing to hook it up to user input/output in an ergonomic-enough way to play Tetris.