Problems with control "Folder Scrollbar" panel via mouse wheel

[Comrade-komissar]

Describe the bug When you move "Folder Scrollbar" panel with mouse wheel, it displays the movement incorrectly - it shows large movement of slider at first moment, but then it decreases to real value. Also there are problem with the logic of interaction between "Folder Scrollbar" and "Thumbnails" panel, they have opposite directions for control with mouse wheel, although they serve the same function. It lead to problem with navigation at folder.

To Reproduce Steps to reproduce the behavior:

1. Click on 'Panels->Folder Scrollbar'
2. Click on 'Panels->Thumbnails'
3. Place mouse at 'Folder Scrollbar' panel and use mouse wheel to scroll images
4. See incorrect position of slider at 'Folder Scrollbar'

Expected behavior "Folder Scrollbar" and "Thumbnails" panels have same direction for mouse wheel control with mouse wheel. Movement of slider at "Folder Scrollbar" shows correctly.

Desktop (please complete the following information):

• OS: Windows 10 Home
• Version 3.16.1709 [x64]