We seem to see darkening effects in ST:GEN where raw starlight becomes a soft yellow glow through 10-Fwd and Picard's cabin windows.
However, I don't think we ever see effects as explicit as the "curtain" that falls over the lounge window in Blade Runner, for example.
We see conventional shutters every now and then. In "Mark of Gideon", Kirk's ship has those on some corridor windows. In DS9, the runabout side windows are frequently seen shuttered by mechanical hatches after the first few seasons - allowing TPTB to leave out the costly starfield effect. Presumably, then, if there was a shipwide desire to prevent the use of windows for viewing purposes, such hatches would slam shut, instead of a darkening effect kicking in.
Presumably the hatches aren't markedly stronger than the windows, though, or else we'd see the shutters slam more often in various crises. The hatches are apparently only for blocking the passing of radiation, perhaps chiefly in situations where the ship tries to hide her emissions from an enemy.
(Also, a tiny little hobby foal here: the hatch we see in ST:FC doesn't look like it would close a window. Rather, it closes a hole blocked by a forcefield, in a room apparently dedicated to operating that hole somehow, with assorted consoles and whatnot. It's probably some sort of an access hole for when the ship is docked to a starbase.)
Timo Saloniemi