How do I detect if a sprite is in the viewport?

I have a scrolling background, a building with window. As the viewport scrolls, windows will come in and out of view of the user. I would like images to appear in the windows every few seconds but only if the windows are in the current viewport. Each window is represented as a sprite on top of the background. How do I detect if the current sprite is within the viewport? Thanks!

I think you can find in documentation.

Its in common condition

"Is on-screen:

True if any part of the object's bounding box is within the screen area. This is not affected by the object's visibility or opacity."

Thank you - that was exactly what I was looking for!