Fast vertical scrolling will make the list stuttering while drawing

[Coldzer0]

Hello guys

I was doing some testes with TVirtualStringTree and I found out that when I scroll fast this stuttering happen. At first I thought that it's from my code or some options I changes but when I tested it with the already shipped examples it's the same.

This is noticed if I use the scroll bar with touch scrolling on a laptop or using the mouse to drag the bar down fast.

Here's a screenshot of the problem

I tested the same scenario with normal Delphi TListView with Double Buffering Enabled and it's very smooth. (without the Double Buffering It will have the same problem but not as bad as TVirtualStringTree)

I tested it with Delphi 11 on Windows 10 And Windows 11 (Latest update for both).

Thanks.

[joachimmarder]

We are intensely using the Virtual TreeView control in our applications like TreeSize Professional and never saw this behavior.

Your screenshot seems to be taken from a modified sample project. Can you please attach the full source code of this project? I was unable to replicate the issue here.

[Coldzer0]

Hello @joachimmarder

It's the same sample as in Virtual-TreeView\Demos\Advanced I just compiled it with Delphi 11 And I tested it on Windows 10 , 11 Latest updates

Here's a GIF shows that When testing with a background the stuttering is gone but with the normal one without it, it has it.

[Coldzer0]

And Here's a screenshot from TreeSize

[joachimmarder]

I am indeed seeing temporary scroll artifacts when using the scroll bar instead of the mousewheel (which I usually use when scrolling) in a themed VCL application. I don't see them when the system style is active. Since you have seen those scroll artifacts in a TListView as well, I suspect a problem in the VCL theme code, which has some known issue in repaint / erase-background code.

I have no idea how I could fix this and since it occurs only as a short and temporary problem when not using the mouse wheel, I see it as low priority.