On Windows, fix set_fullscreen early return for Fullscreen::Borderless(None)

CHANGELOG.md

@@ -19,6 +19,7 @@ Unreleased` header.
 - On macOS, fix `refresh_rate_millihertz`.
 - On Wayland, disable Client Side Decorations when `wl_subcompositor` is not supported.
 - On X11, fix `Xft.dpi` detection from Xresources.
+- On Windows, fix consecutive calls to `window.set_fullscreen(Some(Fullscreen::Borderless(None)))` resulting in losing previous window state when eventually exiting fullscreen using `window.set_fullscreen(None)`.
 
 # 0.29.4
 

src/platform_impl/windows/window.rs

@@ -686,9 +686,19 @@ impl Window {
 
         let mut window_state_lock = window_state.lock().unwrap();
         let old_fullscreen = window_state_lock.fullscreen.clone();
-        if window_state_lock.fullscreen == fullscreen {
-            return;
+
+        match (&old_fullscreen, &fullscreen) {
+            // Return if we already are in the same fullscreen mode
+            _ if old_fullscreen == fullscreen => return,
+            // Return if saved Borderless(monitor) is the same as current monitor when requested fullscreen is Borderless(None)
+            (Some(Fullscreen::Borderless(Some(monitor))), Some(Fullscreen::Borderless(None)))
+                if *monitor == monitor::current_monitor(window.0) =>
+            {
+                return
+            }
+            _ => {}
         }
+
         window_state_lock.fullscreen = fullscreen.clone();
         drop(window_state_lock);