Retain WS_MAXIMZE when unminmizing a maximized window (#2581)

Co-authored-by: Markus Siglreithmaier <m.siglreith@gmail.com>

CHANGELOG.md

@@ -8,6 +8,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 
 # Unreleased
 
+- On Windows, retain `WS_MAXIMIZE` window style when un-minimizing a maximized window.
 - On Windows, fix left mouse button release event not being sent after `Window::drag_window`.
 - On macOS, run most actions on the main thread, which is strictly more correct, but might make multithreaded applications block slightly more.
 - On macOS, fix panic when getting current monitor without any monitor attached.

examples/window_debug.rs

@@ -51,6 +51,7 @@ fn main() {
                     if minimized {
                         minimized = !minimized;
                         window.set_minimized(minimized);
+                        window.focus_window();
                     }
                 }
                 VirtualKeyCode::V => {

src/platform_impl/windows/event_loop.rs

@@ -1185,7 +1185,6 @@ unsafe fn public_window_callback_inner<T: 'static>(
                     w.set_window_flags_in_place(|f| f.set(WindowFlags::MAXIMIZED, maximized));
                 }
             }
-
             userdata.send_event(event);
             0
         }

src/platform_impl/windows/window_state.rs

@@ -299,7 +299,7 @@ impl WindowFlags {
         self = self.mask();
         new = new.mask();
 
-        let diff = self ^ new;
+        let mut diff = self ^ new;
 
         if diff == WindowFlags::empty() {
             return;
@@ -357,6 +357,8 @@ impl WindowFlags {
                     },
                 );
             }
+
+            diff.remove(WindowFlags::MINIMIZED);
         }
 
         if diff.contains(WindowFlags::CLOSABLE) || new.contains(WindowFlags::CLOSABLE) {