feat: add Window::is_visible (#2169)

* feat: add `Window::is_visible`

* use `Option<bool>`

* update doc

* move it right after `set_visible`

src/platform_impl/android/mod.rs

@@ -543,6 +543,10 @@ impl Window {
 
     pub fn set_visible(&self, _visibility: bool) {}
 
+    pub fn is_visible(&self) -> Option<bool> {
+        None
+    }
+
     pub fn set_resizable(&self, _resizeable: bool) {}
 
     pub fn is_resizable(&self) -> bool {

src/platform_impl/ios/window.rs

@@ -60,6 +60,11 @@ impl Inner {
         }
     }
 
+    pub fn is_visible(&self) -> Option<bool> {
+        warn!("`Window::is_visible` is ignored on iOS");
+        None
+    }
+
     pub fn request_redraw(&self) {
         unsafe {
             if self.gl_or_metal_backed {

src/platform_impl/linux/mod.rs

@@ -321,6 +321,11 @@ impl Window {
         x11_or_wayland!(match self; Window(w) => w.set_visible(visible))
     }
 
+    #[inline]
+    pub fn is_visible(&self) -> Option<bool> {
+        x11_or_wayland!(match self; Window(w) => w.is_visible())
+    }
+
     #[inline]
     pub fn outer_position(&self) -> Result<PhysicalPosition<i32>, NotSupportedError> {
         x11_or_wayland!(match self; Window(w) => w.outer_position())

src/platform_impl/linux/wayland/window/mod.rs

@@ -270,6 +270,11 @@ impl Window {
         // Not possible on Wayland.
     }
 
+    #[inline]
+    pub fn is_visible(&self) -> Option<bool> {
+        None
+    }
+
     #[inline]
     pub fn outer_position(&self) -> Result<PhysicalPosition<i32>, NotSupportedError> {
         Err(NotSupportedError::new())

src/platform_impl/linux/x11/window.rs

@@ -984,6 +984,11 @@ impl UnownedWindow {
         }
     }
 
+    #[inline]
+    pub fn is_visible(&self) -> Option<bool> {
+        None
+    }
+
     fn update_cached_frame_extents(&self) {
         let extents = self
             .xconn

src/platform_impl/macos/window.rs

@@ -502,6 +502,12 @@ impl UnownedWindow {
         }
     }
 
+    #[inline]
+    pub fn is_visible(&self) -> Option<bool> {
+        let is_visible: BOOL = unsafe { msg_send![*self.ns_window, isVisible] };
+        Some(is_visible == YES)
+    }
+
     pub fn request_redraw(&self) {
         AppState::queue_redraw(RootWindowId(self.id()));
     }

src/platform_impl/web/window.rs

@@ -89,6 +89,11 @@ impl Window {
         // Intentionally a no-op
     }
 
+    #[inline]
+    pub fn is_visible(&self) -> Option<bool> {
+        None
+    }
+
     pub fn request_redraw(&self) {
         (self.register_redraw_request)();
     }

src/platform_impl/windows/window.rs

@@ -97,6 +97,11 @@ impl Window {
         });
     }
 
+    #[inline]
+    pub fn is_visible(&self) -> Option<bool> {
+        Some(unsafe { winuser::IsWindowVisible(self.window.0) == 1 })
+    }
+
     #[inline]
     pub fn request_redraw(&self) {
         unsafe {