Onyx boox: much worse smoothing when editing existing notes

[Iey4iej3]

Describe the bug

When we edit a note created on a former FOSS Saber version, smoothing of handwriting is much worse

To reproduce

1. Create a note on a previous FOSS version of Saber.
2. Open the note in question under latest Saber with onyxsdk.
3. Edit the note by writing something.

After some seconds of preview, the actual trace on the note is much worse than the preview, extremely non-smooth.

This also happens when we create a new note, but it is notably worse and unsatisfactory for editing preexisting notes created on a previous FOSS version.

Expected behavior

The note is as smooth as the preview.

Saber version

v1.29.0 Google Play (129000)

Device

• Device: Onyx Boox Note Air 3C & Go 10.3
• OS: Android 12

Anything else?

I upload two sba files in a zip file. The "FOSS" file is created on Saber v1.28.2 (F-Droid) and edited by v1.29.0 (Play Store), and the "Play" file is created on v1.29.0 (Play Store). The smoothness of the two notes is visibly different.

https://github.com/user-attachments/files/23699158/saber-debug.zip

Before submitting an issue, please check the following

• I have searched for similar issues (both open and closed) and cannot find a duplicate
• I agree to follow the Code of Conduct

[adil192]

Does the smoothing only happen at low zoom levels? Can you share a screenshot?

[jdkruzr]

for the record I've never had a good experience with Saber with the Go 10.3; it is as if the after-rendering can't keep up with the original trace that it makes and it "drops" a bunch of points in the middle of strokes. my sense is that the Snapdragon 680 just can't keep up. the 3C has the same chip, I think.

ETA: OH MY GOD IT'S FLAWLESS NOW?????? @zinstack625 YOU ARE A GOLDEN GOD, THANK YOU!!!

[Iey4iej3]

Does the smoothing only happen at low zoom levels? Can you share a screenshot?

My zoom level is 1.0x. This only happens under onyxsdk version.

I might produce a screenshot or an sba (if it is possible to export only one page).

[Iey4iej3]

To be more precise, by smoothing, I do not mean it being smoothed during zooming, but (supposed) smoothing of collected data from onyxsdk. That is to say, there is a notable difference between the previewed handwriting and the note.

I upload two sba files in a zip file. The "FOSS" file is created on Saber v1.28.2 (F-Droid) and edited by v1.29.0 (Play Store), and the "Play" file is created on v1.29.0 (Play Store). The smoothness of the two notes is visibly different.

saber-debug.zip

[zinstack625]

Gonna chime in and say that nothing that happens in the preview is related to what happens on the actual note. Code responsible for getting input data is completely independent from what's happening in the onyxsdk overlay and onyxsdk overlay does not report anything to dart.

My guess is 1) the overlay may cause data races in dart callbacks or 2) even make android deprioritize canvas surface and skip calling some of those callbacks due to that surface technically being in the background and not directly interacted with.

If the first is true, then idk, but saber would need deep architectural restructuring, some useless adapters, maybe lots of suffering and some misery to receive stylus data from this overlay and it's very not worth it. A toggle to disable this overlay somewhere in settings would be nice though.

If the second is true, maybe setting the overlay dimensions in dart to 0 could help. I think onyx shenanigans don't care about their actual underlying surfaces, so placing this overlay wherever and making it zero-sized should still keep it working, while android should think that canvas surface is being interacted with

[jdkruzr]

it may or may not be worth noting that Notable also uses the SDK and I don't think it suffers from these issues, but it also doesn't use Dart or Flutter.

[Iey4iej3]

The issue that I encountered might be solvable within Saber, as it is better on newly created notes, but I have to edit notes created on FOSS versions.