[SLATE] SExpandableArea Image, Hover, etc.

Hey there,

I’m currently trying to create an Editor Plugin and it took me a few hours already just searching the Engine.
My problem is the following:

I want something like the “World” Category Area to expand and collapse.

https://puu.sh/tm9ik/7bd0735aab.png

I searched around a bit and I found an AnswerHUB post that suggested not using the “SDetailCategoryTableRow”, but the “SExpandableArea” Widget. I did that, but now I face the problem of not having any border background to it.

https://puu.sh/tm9nD/15f83a59ce.png

I tried doing this:

.BorderImage( FEditorStyle::GetBrush( "ToolBar.Background" ) )

But it seems to have 0 effect (still not background). The “SDetailCategoryTableRow” has a function that selects an Image based on Expanded or not and Hovered or not, but that’s bound when the Widget is created. That would need me to create my own child of “SExpandableArea”, which I kinda don’t want if not needed.

I searched further and tried to add an “FExpandableAreaStyle”, but although this features “Collapsed” and “Expanded” images, setting them still has no effect and it’s also not using anything for the IsHovered state.

So how would I do that? Do I really need to have my own Child and implement that myself by recreating the Header from scratch?

For now I created a Child of “SExpandableArea” and reimplemented the HeaderWidget with a “SBorder” in front of it.
Then I wrote my own function to select the BackgroundImage, similar to the Details Widget.
Works for now.