Explicitly name window size constant

separating out and committing pieces in an old WIP. Don't know what
specifically prompted this change.

src/bin/vrtue.rs

@@ -9,9 +9,10 @@ extern crate piston;
 extern crate piston_window;
 
 use self::piston::input::{Button, ButtonArgs, Input, Key};
-use self::piston_window::{PistonWindow, Window, WindowSettings};
+use self::piston_window::{PistonWindow, Size, Window, WindowSettings};
 use std::env;
 
+const WINDOW_SIZE: Size = Size { width: 1024, height: 1024 };
 
 pub fn main() {
   env_logger::init().expect("env logger");
@@ -21,7 +22,7 @@ pub fn main() {
   };
 
   let mut window: PistonWindow =
-    WindowSettings::new("Hello, Britannia!", [1024; 2])
+    WindowSettings::new("Hello, Britannia!", WINDOW_SIZE)
         .exit_on_esc(true)
         .vsync(vr.is_none())  // Let VR throttle framerate, if available
         .build().expect("Building Window");