Laggy Scrolling in Viewer

[ProfessorCode212]

Scrolling through the Markdown viewer is quite laggy and not as smooth as it should be.

joplin_scoll_issue.mp4

Environment

Joplin version: 1.7.11
Platform: Linux
OS specifics: Linux Mint 19.3, AppImage

Steps to reproduce

1. Open a note.
2. Scroll through the note with the Viewer.

Describe what you expected to happen

Scrolling should be smooth and seamless without 'breaking' in the middle.

[tannercollin]

I'm also having this issue in the full markdown viewer (not only side-by-side). Unfortunately the bug makes this view pretty useless.

Peek.2021-05-19.02-04.mp4

[ProfessorCode212]

@tannercollin It's the same for me as well, although I only showed it using Split View.

[stale]

Hey there, it looks like there has been no activity on this issue recently. Has the issue been fixed, or does it still require the community's attention? This issue may be closed if no further activity occurs. You may comment on the issue and I will leave it open. Thank you for your contributions.

[ProfessorCode212]

I updated to version 2.0.11 and the problem still exists.

[qrsp]

I have the same issue when zooming out the layout, but scrolling smoothly on Actual Size

[tannercollin]

Yup, still a problem on v2.1.7 but only when zoomed in or out. Default zoom (Ctrl+0) fixes the issue, but then everything's too small to read. 👓

[stale]

Hey there, it looks like there has been no activity on this issue recently. Has the issue been fixed, or does it still require the community's attention? This issue may be closed if no further activity occurs. You may comment on the issue and I will leave it open. Thank you for your contributions.

[tannercollin]

Still a problem on v2.1.9.

[tannercollin]

@laurent22 why was the "bug" label removed?

[didaktiik]

I had this scrolling issue since I have started using Joplin. Scrolling becomes laggy often and randomly. I wish the so called "smooth" scrooling could be disabled. You know the old fashioned "jumpy" scrolling which scrolls just 3 lines or so. It's faster as well. Firefox still has the option to turn off the smooth scrolling.

Joplin is the only application I am unable to "force" not to use smooth scrolling. Too bad, I love Joplin otherwise :-)

[stale]

Hey there, it looks like there has been no activity on this issue recently. Has the issue been fixed, or does it still require the community's attention? This issue may be closed if no further activity occurs. You may comment on the issue and I will leave it open. Thank you for your contributions.

[ken1kob]

I analyzed this issue and found a workaround.

As the above reports said, this symptom happens in the Markdown viewer when zoomFactor is not 1. So, users of HD displays may often suffer this symptom.

The following is an example of debug log of this symptom collected when displaying "Welcome to Joplin!" note with 1-level zoom out. To collect this log, I scrolled down the note slowly and tried several mice to confirm there is no hardware malfunctions or operational errors. Each line shows the state of joplin-container-content element for each scroll event.

note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=277.77777099609375
note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=276.66668701171875
note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=277.77777099609375
note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=276.66668701171875
note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=278.8888854980469
note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=277.77777099609375
note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=276.66668701171875
note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=277.77777099609375
note-viewer/index.html: scrollH=2970 clientH=687 scrollTop=276.66668701171875

As you can see, even though I were constantly scrolling down, the values of scrollTop goes up and down and cycles.

Since DOM element's scrollTop is calculated by the upstream (Electron or Chromium) and they are implemented by C++, Joplin cannot interere. So, the symptom is not caused by Joplin.

Such troubles like this symptom have been frequently reported in these years after features about subpixel/zoomFactor are introduced. You can see many open/closed bugs of Chromium here.

A workaround is not difficult. It is enough to calculate scrollTop by yourself. It is the reason the Markdown Editor (CodeMirror), the WYSIWYG editor (TinyMCE) and other popular products are free from this symptom.

Soon, I'll send a pull request fixes the issue.