The scroll bar in a scroll box does not currently indicate that it is interactable. The UWidgetInteractionComponent::IsOverInteractableWidget() function returns true if it is over a button, but returns false if it is over a scrollbar. Since the scroll bar is actually interactable, it is expected that this would be indicated the same way that it is for a button.

The user that reported this suggested that adding the following code to the public section of the SScrollBar class should resolve the issue:

virtual bool IsInteractable() const override
    return IsEnabled();

He also suggested that all interactable SWidgets should probably override IsInteractable() in the same way.

Steps to Reproduce
  1. Download the attached project.
  2. Associate with your version of Main (project was made using CL 3236017).
  3. Open the project in the Editor.
  4. Start PIE.
  5. Move the mouse over the 3D Widget in the scene.

The on-screen message displays "true" when the mouse is over one of the buttons in the widget, but when the mouse is moved over the scrollbar the message displays "false."

The on-screen message displays "true" both when the mouse is over one of the buttons as well as when it is over the scrollbar.

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ComponentUE - Editor - UI Systems
Affects Versions4.14.14.15
Target Fix4.16
Fix Commit3250738
Main Commit3279775
CreatedDec 15, 2016
ResolvedJan 9, 2017
UpdatedSep 6, 2020