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Comment by JeanMarcS | Hacker News Reader

Don't know about the code subtilities, but SumatraPDF is a gift for viewing PDF on MS Windows. So big thanks to the author !

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Out of curiosity, what's your use case for it? Years ago I preferred Sumatra/Foxit to Adobe, but every major browser has supported rendering PDFs for at least a decade and I haven't had needed or wanted a dedicated PDF reader in all that time.

Part of why I use SumatraPDF is that it automatically reloads its view when the files change (at least for PDFs, I haven't tested on the other file types it supports).

That's not always desirable though. I'd rather have control over that

You have, via a config. You have no control in a browser.

same here--I can't imagine using latex without this feature. To me it's a beautiful piece of software, the only thing I keep pinned to the taskbar other than wsl shell.

It's smaller, lighter and much faster than launching a web browser to view a PDF. I can configure it to open a new instance for each PDF which is nice if you need to have several docs open at once. Again, nothing that you can't do with a browser and dragging tabs, but I prefer this.

Not only is it faster in opening than a browser and a separation of concerns (documents get their own app, which I can leave with open tabs), it also opens epub, .cbz, and other formats, so I have it installed on all my Windows machines. I eventually open a book.

Not the OP, but my use case is epub books, which it handles flawlessly.

Large PDFs are very slow in browsers. I believe they all use pdf.js (or similar).

firefox uses pdf.js, but chromium uses pdfium and safari uses pdfkit

PDFkit seems similar in that it is JS. Is it also slow?

I just tried a few PDFs in Chromium and PDFium seems to be much better than pdf.js - faster and handles forms more smoothly.

PDFkit seems to be a name a few different things in stuff like node and ruby. I think the Apple PDFkit is probably just wrapping Apple’s in house PDF tech that Preview uses?

It does not seem to have any requirements than JS - browser or Node. There is an online demo that works with Firefox on Linux so not wrapping anything else.

the pdfkit from the first google result doesn't seem to be related to apple's. what happened here is that "pdfkit" is a very generic name (that will tend to show up because people love writing pdf-related software) that also happens to coincide with apple's convention of naming their frameworks something-kit (uikit, appkit, avkit, ...)

> use case

Sumatra excels at read-only. Usually anything to do with PDF is synonymous with slow, bloat, buggy, but Sumatra at just 10Mbytes, managed to feel snappy, fast like a win32 native UI.

Opening a pdf inside a browser feels to me like an application inside an application. My brain can't handle that load. I would rather have the browser to browse the internet and a pdf reader to display pdfs. If I clicked on a link to a pdf, it is _not_ part of the web, and I want the browser to stay out of it. Same goes for Office 360 wanting to documents inside my browser. I don't want it to do that. I have the necessary apps installed for it.

I really would not like to ruin the entire internet for you, but isn't the vast majority of websites these days fully fledged applications, hence applications in application in the sense you mentioned ?

I would argue that a pdf reader is much simpler than multiple very popular webpages nowadays.

> the vast majority of websites these days fully fledged applications

Many apps do exist on the web. Not many of them are very good, PDF is a bit case in point - web struggles to fully implement PDF read/write (partly a complexity thing, partly I'm sure a tactic non-compete with Adobe).

Even more sites still exist that aren't apps, even if a few big sites have stolen people's imaginations...

So two reasons why you don't really want your PDF in the browser (I don't mind much if I'm never going to look at it again but otherwise no I don't want it in my browser).

Even if the first two weren't true, there's still just the fact that, no, PDF is local, web is not. I don't need an internet connection for one, and I don't need to worry about one messing with the other. Sounds like a strange thing to worry about, but browsers do crash, and more importantly browsers are often filled with tabs. You can have many PDFs open but you don't need to keep them all in memory...

I didn't mention any particular sense about application inside an application. I did say how it "feels like to me" and how my brain fails to handle it. There is a clear shift of modes when I click on a link on a website and suddenly the contents of the current browser window are replaced by a pdf with its own back and forward buttons, its own page layout, its own toolbar and so on. If it stopped feeling different like that, I would not even notice it and wouldn't even bother to find out if what I am seeing is a pdf or an html based website.

How do you alt tab to a browser tab with a PDF? How do you change navigation shortcuts when browsers are notoriously bad at such customizations?

Sumatra will reload any PDF that changes while you are viewing it (Adobe locks the file, so you can't change it to begin with). This is incredibly useful when you are writing documentation using a document generating system (like docbook).

in my experience, browser pdf viewers take a loooot more RAM than Sumatra

As I still recalled it's possible to configure an external editor so that when you click on any place on sumatraPDF viewer you can open the source file that is annotated with the clicked position. This is extremely helpful when working with LaTeX documents.

It is not sandboxed.

So one can expect zero day exists and are exploited.

That may not be a feature for you, but it is for attackers.

Does it implement any of the dynamic features in PDF that are vectors for easy attacks like that?

PDF was originally a display-only format.

You don't need any dynamic features in PDF to attack. One of the most famous exploits used a bug in the JBIG2 format to build the attacker's own dynamic feature (basically a virtual machine built from logic operations) to launch an exploit. https://googleprojectzero.blogspot.com/2021/12/a-deep-dive-i...

In fact you have gotten it backwards. The obviously dynamic features in PDF like JavaScript are designed to be dynamic so they receive so much more attention in security. So smart attackers attack the not-obviously-dynamic features in PDF.

Ah, very good point.

Sumatra has more security features than most other readers?

For example, it doesn't support JavaScript. And it doesn't support GoToE.

The text features, both strings and fonts, get sent through HarfBuzz for sanitisation.

How is it not sandboxed?

If you hate it when pdfs won't print because of restrictive permissions... Sumatra.

> I haven't had needed or wanted a dedicated PDF reader in all that time.

OK. Now load 100 PDF's. You will need a dedicated PDF reader unless you don't mind wasting a truckload of RAM. Also, browser PDF readers are generally slower and are not optimal at search/bookmarks/navigation/etc.

I've never needed to load 100 PDFs at once, and honestly I don't imagine I ever will. I guess it might happen for some people, so a dedicated app would be useful for them.

For me, having a separate dedicated app isn't worth it for the benefits you mention, which to me are minor compared to having to install and manage another thing (which, to be fair, I imagine Sumatra to be a very pleasant citizen at compared to Acrobat).

Even just 10 PDFs is leaner than a similar number of bloated web pages.

Documentation particularly is a big one. Then there are books, etc.

Some web pages can still manage to be leaner than a PDF, but as another poster pointed out, a lot of modern web is pretty trash...

opening (and browsing/searching through) a very large PDF is a nightmare in most browsers

I use my browser for most PDFs. But for PDFs that have a lot of vector graphics and are over 50-100mb, the browser viewer is very slow to load and render the pages. Even zooming in on a part of a drawing can take 10-15 seconds in the browser which is pretty disruptive.

Sumatra has no issues with 200mb+ PDFs, or ones with complex drawings.

These are all engineering drawings such as mechanical, electrical, and architectural drawings, so mine might not be a use case everyone has.

> But for PDFs that have a lot of vector graphics and are over 50-100mb

I also have opened Lenovo Thinkpad manuals, hahaha. For those who haven't, it's quite amazing, really: the SVG images are exports of the full CAD model of the laptop without any culling of elements that aren't visible. And I know this because I used to see each indiduad screw be rendered slowly afer the other whenever pdf.js tried to render one of those bad boys.

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