To use ActiveShade, you must use Nitrous drivers as legacy drivers are not supported. ActiveShade can only be displayed in one window or viewport at a time.
To display ActiveShade in a viewport:
Scanline rendering is not supported in the viewport. To render in Scanline, you must use the free-floating ActiveShade window.
To display a free-floating ActiveShade window:
To zoom and pan in an ActiveShade floating window:
You can zoom in and out and pan the image in the ActiveShade floating window. You can even do this while a scene is rendering.
If you have a three-button mouse, you can use its third button or wheel to zoom and pan:
To update a Scanline ActiveShade floating window after moving an object or changing object geometry: