3d Viewer Shadow link to Sun Lamp

Is it possible to link a light source (sun) to generate shadows in the viewer? I refer to the shadows of the "shading" menu of the 3d viewer.

I propose two possible ways to integrate it:

• A selector in the shading menu of the 3d viewer as currently the selectors of Blender 2.79 with the keyboard shortcut "E" (the eyedropper).
• A checkbox in the preferences of the sun type lights. (use for shadows in 3d viewer)

(I hope Google has done a good job with my English)