I want to create a program/app (not a game) and use Slate widgets displayed in the window which is always on top. Not only on top of other Slate windows but also other native OS windows.
Is it even possible right now in Slate? If so where do I start? If not, can I put widgets in native OS window?
To answer the original question, you can get a slate window to always be on top quite easily. Here is the relevant code when creating a new window.
auto Window = SNew(SWindow)
.Title(LOCTEXT("WindowTitle", "ArchVizTools"))
.IsTopmostWindow(true) // <------ Makes the window always stay on top
.ClientSize(FVector2D(200.0f, 600.0f))
.SupportsMaximize(true)
.SupportsMinimize(false)