Portrait image does not drag smoothly

[kwvanderlinde]

Describe the bug

The dragging of the portrait image is not at all smooth. After dragging the mouse, it takes a long time for the portrait position to be changed.

It also seems that new mouse drags preempt responses to previous mouse drags. I.e., the portrait image only tends to move when I've either released the mouse button, or hold the mouse still for a little bit. If I continously drag the image, the position never updates.

Meanwhile, while dragging the image my CPU fan goes wild, suggesting there's a lot of work being done.

To Reproduce
Steps to reproduce the behavior:

1. Open TokenTool
2. Set a portrait image
3. Drag portrait image around.

Expected behavior

The portrait image should closely follow the mouse dragging movements.

Screenshots

TokenTool Info

• Version: 2.2.2
• Install: New

Desktop (please complete the following information):

• OS: Linux Mint
• Version 22.1

Additional context

[Phergus]

I don't see this behavior under Windows 10.

[kwvanderlinde]

I see Windows lag as well, but it's nothing close to what I see on Linux Mint.

Did a little bit of investigating, and it's because of how we generate the preview images. Not sure exactly what detail is to blame, but I'd guess it's all the snapshotting that goes on. Either way, if I disable the preview generation, then drags become very smooth on both Linux and Window.

[Phergus]

Interesting. On my system I see CPU go to about 20% and GPU goes to 40% while dragging. It's a bit stuttery but still completely usable. CPU: i7-11700K GPU: RTX 3060

Sounds like it could and should be improved however.

[kwvanderlinde]

Not sure exactly what detail is to blame, but I'd guess it's all the snapshotting that goes on.

Yep, definitely the snapshots. They're blocking, and we potentially do several of them to generate a single preview. That's fine in itself, but for some reason on Linux it can also prevents a new frame from being shown. I'll just chalk that up to some deficiency in JavaFX's platform support for Linux as it's often not as polished as for other platforms.

There is a callback-based snapshot method that doesn't block. Using that helps a lot and makes TT on Linux feel as smooth as on Windows.