Whether or not to paint a translucent white on top of this surface's blurred background. isSurfacePainted should be true for a typical popup that contains content without any dividers. A popup that requires dividers should set isSurfacePainted to false and then paint its own surface area.
Some popups, like iOS's volume control popup, choose to render a blurred area without any white paint covering it. To achieve this effect, isSurfacePainted should be set to false.
final bool isSurfacePainted