glitchy zoom behaviour in PDF viewer

Hi there

I have noticed that the zoom behaviour in the Zotero PDF viewer is rather glitchy, at least on my system, which is a laptop with extra external screen, bluetooth keyboard and wireless mouse. All of these things function perfectly normally with other software.

In particular, using ctrl+mouse wheel to zoom the Zotero PDF viewer, I find that sometimes it responds, and sometimes it does not. When it does not work, I have to release the 'ctrl' key, wait a moment, then press it again, then attempt spinning the mouse wheel again. I think that the main issue comes when combining zoom actions with scroll (up and down) actions. After a no-ctrl mouse wheel spin, if I press ctrl and then spin the mouse wheel again, no event is caught and nothing happens. If I press and release ctrl once before attempting the mouse-zoom, then it works fine.

This issue significantly affects the usability of the Zotero PDF viewer for me, since I am often zooming in and out to examine the details of figures, etc.

Here is my report ID, with all my Zotero version details: 1650466127

  • I have observed a time delay when switching from scrolling to zooming, as detailed in this post:

    Is it the same problem?
  • i think you're right. it looks like it might be more of a delay issue than a ctrl-key issue as I first suspected.
  • @jdpipe @mjthoraval Does it work better if you open a PDF file in Firefox built-in PDF reader (Zotero uses the same reader)?
  • I see the same behaviour in Firefox (both 109.0.1 (64-bit) & 110.0b9 (64-bit)).
    I see the problem even for small text files, so it is not related to the size of the file.
    Adobe Acrobat, Foxit, Edge, ... are all working smoothly without delay for exactly the same PDF files.
    I see the problem with or without external monitors, so it does not seem to be the issue either.

    I see more clearly the time delay by using the Infinite Scroll Wheel of my Logitech mouse (MX Master) and pressing Ctrl during the infinite scroll. The vertical scrolling stops for 1 or 2 seconds after pressing Ctrl, and it then eventually starts zooming if the wheel is still spinning.
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