undefined | Better HN

0 pointsduskwuff5y ago0 comments

PDF is not a stack machine. This is a common misconception.

PostScript was a stack machine with included operators which implemented a set of vector graphics commands. PDF has a similar rendering pipeline, but it renders a set of primitives described directly in the document -- there is no virtual machine involved.

0 comments

zepto5y ago

My understating is that PDF still has a stack machine. Just one that is much simpler.

Having said that, PDF is vastly more complex than it was originally. It can contain forms, JavaScript, audio, video, accessibility metadata, etc.

It’s an extremely complex format.

buckminster5y ago

Yes, but it's easy to generate a valid pdf. You just include the features you need and ignore the rest. It's really hard to transform an arbitrary pdf because you need to handle all the features.

Without further information this is more likely to be an Apple bug because they are doing the harder job.

zepto5y ago

One point: Transforming an already incorrect file into a correct one is the hardest job of all.

Plus some further information:

ABBY has had months to support Big Sur but still haven’t.

That makes it seem like they either don’t care about supporting MacOS users, or they have a very low engineering budget.

Either way, that makes it seem more likely to me that they have a bug, than Apple.

But, regardless of the balance of probabilities, the point is that the original piece blames Apple entirely.

And yet nobody here really seems to dispute the idea that ABBY, a professional PDF generator could be producing a buggy file.

j / k navigate · click thread line to collapse

0 comments

zepto5y ago

My understating is that PDF still has a stack machine. Just one that is much simpler.

Having said that, PDF is vastly more complex than it was originally. It can contain forms, JavaScript, audio, video, accessibility metadata, etc.

It’s an extremely complex format.

buckminster5y ago

Yes, but it's easy to generate a valid pdf. You just include the features you need and ignore the rest. It's really hard to transform an arbitrary pdf because you need to handle all the features.

Without further information this is more likely to be an Apple bug because they are doing the harder job.

zepto5y ago

One point: Transforming an already incorrect file into a correct one is the hardest job of all.

Plus some further information:

ABBY has had months to support Big Sur but still haven’t.

That makes it seem like they either don’t care about supporting MacOS users, or they have a very low engineering budget.

Either way, that makes it seem more likely to me that they have a bug, than Apple.

But, regardless of the balance of probabilities, the point is that the original piece blames Apple entirely.

And yet nobody here really seems to dispute the idea that ABBY, a professional PDF generator could be producing a buggy file.

j / k navigate · click thread line to collapse