Add Window::is_maximized method (#1804)

src/platform_impl/windows/window.rs

@@ -385,6 +385,12 @@ impl Window {
         });
     }
 
+    #[inline]
+    pub fn is_maximized(&self) -> bool {
+        let window_state = self.window_state.lock();
+        window_state.window_flags.contains(WindowFlags::MAXIMIZED)
+    }
+
     #[inline]
     pub fn fullscreen(&self) -> Option<Fullscreen> {
         let window_state = self.window_state.lock();

src/platform_impl/windows/window_state.rs

@@ -34,7 +34,7 @@ pub struct WindowState {
     pub current_theme: Theme,
     pub preferred_theme: Option<Theme>,
     pub high_surrogate: Option<u16>,
-    window_flags: WindowFlags,
+    pub window_flags: WindowFlags,
 }
 
 #[derive(Clone)]