Min: weird zoom behavior in PDF files

[shalva97]

• Min Version: 1.15.0
• Operating system:
  Arch Linux

Expected Behavior

• pressing CTRL + - twice should zoom out twice
• single wheel scroll should zoom

Actual Behavior

• pressing CTRL + - zooms out twice but sometimes it also scrolls the PDF
• single mouse wheel scroll doesnot do anything when holding CTRL

To Reproduce

• scroll to the middle of the PDF then play with zooming, by about 3rd zooming in, the page will scroll up
• slowly scroll the wheel one by one while holding CTRL

[PalmerAL]

This is probably the same root cause as #1207, so I would expect it to be fixed in the next release.

[PalmerAL]

@shalva97 Does this work for you now in the latest release?

[shalva97]

nope... no difference.

sometimes,when zooming in, webpage stays blury. or if it can focus webpage scrolls. but i cannot find and exact steps to reproduce. This is quite random... but almost 75% of the time if i scroll to middle of PDF, wait for pages to load, zoom in, zoom out and it will scroll one page up

pdf i was testing this with

[PalmerAL]

Thanks. I think I have a fix for the scrolling while zooming issue here: 5b5e1fc2de555fecb6d01dd81a9b0f59b2f181e2, but since it only happens inermittently like you mentioned, it's difficult to tell for sure. If you're willing to, it would be great if you could try running Min using the instructions in the readme and seeing if that fixes it for you.

Scrolling while pressing ctrl works for me on a trackpad; I'll try it out on a mouse later.

[shalva97]

wow that is some magical one line fix for random scrolling ;D

okay, mouse scrolling issue left only... and i guess it was bad idea writing 2 issues into one issue....

[PalmerAL]

Yeah, the scroll issue is kind of interesting; that line disables scroll anchoring, which is a Chromium feature that tries to scroll the page so that the content you're looking at stays in the same place as the page changes. I suspect there's a Chromium bug that makes it not work correctly with the PDF viewer, but it isn't necessary there anyway, so it's fine to just disable it.

I can't reproduce the zoom issue with a mouse, but I think it may have to do with how sensitive your scroll wheel is (mine is fairly sensitive). Can you try this:

Right click on the PDF viewer > inspect element > console > paste this code and press enter:

document.addEventListener('wheel', e => console.log(e.deltaX, e.deltaY, e.metaKey, e.ctrlKey, e.deltaMode))

and post the resulting output here?

Also, does the issue happen on normal webpages as well, or just the PDF viewer?

[shalva97]

oh, it actually happens everywhere... here is my logs and it only zooms in if the output is greater than 53.
In firefox it is always -3 and never goes above that

[PalmerAL]

Thanks! This should be fixed by 61429877560451ff7bd0c9928c918685ec70bdcd; if you could test it that would be great.

[Syndamia]

After some testing on my end, I found out that a mouse doesn't create the scroll while zooming issue, not on the newest release or on the newest master.

However, this problem does occur on both newest release and master while using a track pad.

---

Using the wheel event listener that @PalmerAL provided, using a mouse produced similar results to @shalva97's (no numbers were between -53 and 53):

but using the track pad produced different results, the numbers were primarily from around 1 to 15:

Also, the track pad issue is present everywhere, not only on pdf files.

---

I'm not very knowledgeable of the app and chromium, but isn't there a way to allow page scrolling only when the Ctrl key isn't pressed? I feel like that would fix the issue.

[PalmerAL]

@Syndamia I think that might be a different issue? IIUC, the two issues here were:

• The PDF document would sometimes jump by several pages suddenly when zooming. This is a PDF-viewer specific issue that should be fixed.
• If you scrolled too slowly with ctrl, the page would not zoom in (but it should now).

[shalva97]

@PalmerAL both issues are resolved. Perfect. I would say you got a double kill!

should we close this now?

[kodumbeats]

I think so. @Syndamia, could you open a new issue for this trackpad problem?

[Syndamia]

I think that might be a different issue?

Yes, I misunderstood this issue a bit.

could you open a new issue for this trackpad problem?

Yep, it's #1244.