[myfonj]

I went the rabbit hole of exploring SVG "decimal precision-related" glitches in browser implementations and to my grief I must confirm that there really are blatant cross-browser issues. It's fact that my tests went a bit over-the-top with dimensions -- who would make 1e9 or 1e-9 wide viewBox in real world anyway? -- but since refraining from doing so is not discouraged in the specs, one would expect it would scale (pun intended) at least few orders of magnitude. The results for my particular testcase showed that "safe" range was only between 2e3 and 2e5: [1].

https://myfonj.github.io/tst/SVG-decimal-precision-results.h...

[michaelt]

> who would make 1e9 or 1e-9 wide viewBox in real world anyway?

Back in about 2008 I made an SVG diagram showing the height of various satellite orbits above earth, specifying the SVG at 1:1 scale - making the image 84,000 km wide.

Sadly a load of file viewers choked on it, so I had to settle for a downscaled version. It seems the 'scalable' in 'scalable vector graphics' only goes so far.

[myfonj]

Ha, nice! I secretly hoped someone would mention their real-world usage of "ridiculously" large SVG dimensions, so thanks for the reference!

Your story implies there actually were some viewers that could handle it correctly? Could you recall more details what were they? (My testing was pitifully limited to current browsers only, but I know there must be vast amount of other viewers.)

And if I may ask, did you map one SVG "point" to some length unit (e.g. meter, so getting 84e6 wide wiewBox), or did you assume 90 DPI "pixel" mapping to ~0.2822 mm?

[michaelt]

I've just re-tested, and you're right. This SVG won't display properly with chrome, firefox, inkscape or imagemagick

  <?xml version="1.0" encoding="UTF-8" standalone="no"?>
  <svg width="84000000000mm" height="84000000000mm"
     viewBox="0 0 84000000000mm 84000000000mm"
     version="1.1" id="svg5"
     xmlns="http://www.w3.org/2000/svg"
     xmlns:svg="http://www.w3.org/2000/svg">
    <ellipse
       style="fill:none;stroke:#000000;stroke-width:0.812697;stroke-opacity:1"
       id="path111" cx="42000000000mm" cy="42000000000mm"
       rx="42000000000mm" ry="42000000000mm" />
  </svg>

However the browsers don't crash or run out of memory, so they've got that going for them. And if you embed the image in a web page with <img src='84km.svg' width=1000 height=1000> chromium almost manages to display it.

SVG lets you specify sizes in a bunch of different units, but there's actually a fixed ratio between them - in SVG, 1mm means is 3.78px regardless of your display or printer's DPI.

So I didn't scale mm to SVG's arbitrary length units - but the standard did.

[myfonj]

So at this point we don't know about any viewer capable of handling Earths orbit sized SVG? That's sad.

> However the browsers don't crash or run out of memory

Good news for your sample. Yet in some browsers there prevail some open issues, just the limits are now farther. For example feeding this SVG to my Firefox almost instantly exhausts my RAM and makes the browser window unusable for a while:

    data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg"
     viewBox="-1e11,-1e11,2e11,2e11"><circle r="1e11"/></svg>

I guess for more beefed machines would be necessary to bump exponents slightly higher. It's a known issue [1].

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1864374

[codetrotter]

From looking at the following pages

- https://docs.aspose.com/svg/net/drawing-basics/coordinate-sy...

- https://www.w3.org/TR/SVG2/coords.html

- https://developer.mozilla.org/en-US/docs/Web/SVG/Tutorial/Po...

You can use “cm” and “mm” in SVG.

It will then be up to the viewer program (web browser or which ever program you are using) to make it correct for the DPI of your display.

[nayuki]

I tried to make a daily timeline in SVG where 1 unit = 1 second. There are 86400 seconds in a day. Both Firefox and Chrome did not render the image properly, so I had to scale the numbers down too. What a shame.

[myfonj]

(Missed edit:) I even asked about formalized precision SVG limits on SO: https://stackoverflow.com/q/78692079/540955

[masfuerte]

Also, browsers seem to render svg circular arcs using bezier curves. At high zoom levels there can be quite a discrepancy between the actual curve (drawn using lots of straight line segments, say) and what the browser renders for a circle.

[myfonj]

Do they? I thought this is more issue on the source code side, rather than implementation: this is actually my pet-peeves, that most SVG *authoring tools* never output circular arcs and always use cubic béziers approximations instead. So we nearly ever see real circles or their segments, even though authors use them in their designs all the time.

// Coincidentally played with this test yesterday: https://myfonj.github.io/sandbox.html#%3C!doctype%20html%3E%...

[masfuerte]

It was a few years ago and I'm unable to reproduce it. Circles and circle approximations from straight lines seem to coincide exactly in Firefox and Edge now.

I was generating diagrams using my own code so I'm positive they were circular arcs. Tangents weren't tangent and it took me a while to realise that the problem was the browser rendering something that wasn't quite a circle. I assumed it was a bezier approximation but I didn't verify that. Whatever it was it seems to be fixed.