Yes, of course the "Scrollable" property is checked.
The problem is that when I start the SWT interface, the Scroll of MainBox and also of another tree field with the mouse wheel doesn't work.
For this reason I open this topic, just to understand if it's possibile add the management of this type of event.
I tried it with our demo application and for me it does work.
I have a tree on the left hand side and a MainBox with "Scrollable" set to true. Both, the tree and MainBox show the scrollbars (see attached image). When I focus the tree (click on it) I can use the mousewheel for scrolling. When I focus the MainBox (click on a field for example) the mousewheel scrolls down the mainbox.
Is this similar to your usecase?
Can you check out the project and try to reproduce the problem (add forms, groupboxes, ...)? Currently, the project is working on my machine. Once we have a setup where scrolling does not work anymore, I will try to fix it.