OnPaint slate MyClippingRect argument has changed ?

I don’t know if the argument MyClippingRect of the OnPaint function in widget has changed.
But in version 4.15, it contains the clipping rect of the widget itself.

Now in version 4.17, it seems to contain the entire screen area.

nt32 SKButton::OnPaint(const FPaintArgs& Args, const FGeometry& AllottedGeometry, const FSlateRect& MyClippingRect, FSlateWindowElementList& OutDrawElements, int32 LayerId, const FWidgetStyle& InWidgetStyle, bool bParentEnabled) const
	FSlateRect rect = MyClippingRect;
	FVector2D size = rect.GetSize();

Is it due to the fact all drawing function, like MakeBox, do not take anymore the ClippingRect ?