Hi all,

I'm applying the Ruler path effect to a 20px line, so that there's a mark every 1px and a major mark every 5px. But when I enter the measurements for the path effect, they don't match up to what they're supposed to be.

I have verified this with the measure tool in the attached screenshot. I'm using Inkscape 1.3.2 on Nobara, a distro based on Fedora.

Let me know if any other information is needed.

Thanks!

Likely this bug: https://gitlab.com/inkscape/inkscape/-/issues/4654

What does it mean that it happens when the path has a transform applied? Does it mean that if I draw a path and move it around, it will also show that LPE bug? Does it happen when I resize the path too?

I discovered this bug when trying to make a circular gauge. I was testing to see how the LPE worked by making the markings of a clock. The effect didn't work if there was no stroke, and it distributed the markings along the circumference. So I enabled stroke and removed fill for the circle and calculated a round marking distance using the formula below.

Mark distance = 2 x pi x radius / number of markings

A clock has 60 markings, so a radius of 21px should make the marking distance as 2.2px. But it didn't match up.

I can confirm that it works properly on Windows. I'll try to make the same drawing in Windows and Linux in separate files and upload here. I'll also try opening and editing the Linux file in Windows, and vice-versa, to see what happens.

IIRC, my quick test seemed to work ok when transforms were set to optimized in the Preferences dialog.

FWIW there is also an extension for dials and gauges: https://inkscape.org/~sincoon/%E2%98%85knob-scale-generator

I checked in Edit > Preferences > Behaviour > Transform and found that it's already set to Optimised for both Windows and Linux. Changing to Preserved does make a difference, but it's still wrong. On my experiment to check the LPE behaviour in both OS, I found that it's not consistent in Windows either.

For a 50px line in Windows, the Measure tool shows that it's 49.8px and the last marking is at 0.89px, even if it's drawn with optimised transform. I drew the line using the Pen tool and made it 50px using the options that come up for the Selector tool. While the the clock looks okay in Windows, the preserved transform behaviour seems to have an extra marking at 3 o'clock.

I also noticed that the marking length is also not consistent. It's clearly visible once you see the files in Inkscape.

I have attached the files made in Windows and Linux. I didn't get time to check them in the other OS yet.

Note that the selector tool controls can display the visual or the geometric measurements. In this case I'd set the controls for geometric in the Preferences. This setting will ignore the stroke thickness.

I see in the Linux version document properties, that the scale is set to 3.77953. I would try starting the test with a document template for screen (or set the units to px and the scale to 1); similar to the Windows document.  The scale making a difference is likely revealing a different bug.

Yeah, that seems to have been the problem. The Scale was set to that number in the Document Properties for the default.svg. I set it to 1 and now they all scale properly.

Now, I just gotta make sure the Windows one doesn't have 1.000001 or something like that. Thanks for the help!