Fix assigning the wrong monitor when receiving Windows move events (#2266)

Co-authored-by: kas <exactly-one-kas@users.noreply.github.com>

CHANGELOG.md

@@ -39,6 +39,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On iOS, send `RedrawEventsCleared` even if there are no redraw events, consistent with other platforms.
 - **Breaking:** Replaced `Window::with_app_id` and `Window::with_class` with `Window::with_name` on `WindowBuilderExtUnix`.
 - On Wayland and X11, fix window not resizing with `Window::set_inner_size` after calling `Window:set_resizable(false)`.
+- On Windows, fix wrong fullscreen monitors being recognized when handling WM_WINDOWPOSCHANGING messages
 
 # 0.26.1 (2022-01-05)
 

src/platform_impl/windows/event_loop.rs

@@ -56,17 +56,17 @@ use windows_sys::Win32::{
             GIDC_ARRIVAL, GIDC_REMOVAL, GWL_EXSTYLE, GWL_STYLE, GWL_USERDATA, HTCAPTION, HTCLIENT,
             MAPVK_VK_TO_VSC, MINMAXINFO, MSG, MWMO_INPUTAVAILABLE, PM_NOREMOVE, PM_QS_PAINT,
             PM_REMOVE, PT_PEN, PT_TOUCH, QS_ALLEVENTS, RI_KEY_E0, RI_KEY_E1, RI_MOUSE_WHEEL,
-            SC_MINIMIZE, SC_RESTORE, SIZE_MAXIMIZED, SWP_NOACTIVATE, SWP_NOMOVE, SWP_NOZORDER,
+            SC_MINIMIZE, SC_RESTORE, SIZE_MAXIMIZED, SWP_NOACTIVATE, SWP_NOMOVE, SWP_NOSIZE,
-            WHEEL_DELTA, WINDOWPOS, WM_CAPTURECHANGED, WM_CHAR, WM_CLOSE, WM_CREATE, WM_DESTROY,
+            SWP_NOZORDER, WHEEL_DELTA, WINDOWPOS, WM_CAPTURECHANGED, WM_CHAR, WM_CLOSE, WM_CREATE,
-            WM_DPICHANGED, WM_DROPFILES, WM_ENTERSIZEMOVE, WM_EXITSIZEMOVE, WM_GETMINMAXINFO,
+            WM_DESTROY, WM_DPICHANGED, WM_DROPFILES, WM_ENTERSIZEMOVE, WM_EXITSIZEMOVE,
-            WM_INPUT, WM_INPUT_DEVICE_CHANGE, WM_KEYDOWN, WM_KEYUP, WM_KILLFOCUS, WM_LBUTTONDOWN,
+            WM_GETMINMAXINFO, WM_INPUT, WM_INPUT_DEVICE_CHANGE, WM_KEYDOWN, WM_KEYUP, WM_KILLFOCUS,
-            WM_LBUTTONUP, WM_MBUTTONDOWN, WM_MBUTTONUP, WM_MOUSEHWHEEL, WM_MOUSEMOVE,
+            WM_LBUTTONDOWN, WM_LBUTTONUP, WM_MBUTTONDOWN, WM_MBUTTONUP, WM_MOUSEHWHEEL,
-            WM_MOUSEWHEEL, WM_NCCREATE, WM_NCDESTROY, WM_NCLBUTTONDOWN, WM_PAINT, WM_POINTERDOWN,
+            WM_MOUSEMOVE, WM_MOUSEWHEEL, WM_NCCREATE, WM_NCDESTROY, WM_NCLBUTTONDOWN, WM_PAINT,
-            WM_POINTERUP, WM_POINTERUPDATE, WM_RBUTTONDOWN, WM_RBUTTONUP, WM_SETCURSOR,
+            WM_POINTERDOWN, WM_POINTERUP, WM_POINTERUPDATE, WM_RBUTTONDOWN, WM_RBUTTONUP,
-            WM_SETFOCUS, WM_SETTINGCHANGE, WM_SIZE, WM_SYSCHAR, WM_SYSCOMMAND, WM_SYSKEYDOWN,
+            WM_SETCURSOR, WM_SETFOCUS, WM_SETTINGCHANGE, WM_SIZE, WM_SYSCHAR, WM_SYSCOMMAND,
-            WM_SYSKEYUP, WM_TOUCH, WM_WINDOWPOSCHANGED, WM_WINDOWPOSCHANGING, WM_XBUTTONDOWN,
+            WM_SYSKEYDOWN, WM_SYSKEYUP, WM_TOUCH, WM_WINDOWPOSCHANGED, WM_WINDOWPOSCHANGING,
-            WM_XBUTTONUP, WNDCLASSEXW, WS_EX_LAYERED, WS_EX_NOACTIVATE, WS_EX_TOOLWINDOW,
+            WM_XBUTTONDOWN, WM_XBUTTONUP, WNDCLASSEXW, WS_EX_LAYERED, WS_EX_NOACTIVATE,
-            WS_EX_TRANSPARENT, WS_OVERLAPPED, WS_POPUP, WS_VISIBLE,
+            WS_EX_TOOLWINDOW, WS_EX_TRANSPARENT, WS_OVERLAPPED, WS_POPUP, WS_VISIBLE,
         },
     },
 };
@@ -980,6 +980,37 @@ unsafe fn public_window_callback_inner<T: 'static>(
                     right: window_pos.x + window_pos.cx,
                     bottom: window_pos.y + window_pos.cy,
                 };
+
+                const NOMOVE_OR_NOSIZE: u32 = SWP_NOMOVE | SWP_NOSIZE;
+
+                let new_rect = if window_pos.flags & NOMOVE_OR_NOSIZE != 0 {
+                    let cur_rect = util::get_window_rect(window)
+                        .expect("Unexpected GetWindowRect failure; please report this error to https://github.com/rust-windowing/winit");
+
+                    match window_pos.flags & NOMOVE_OR_NOSIZE {
+                        NOMOVE_OR_NOSIZE => None,
+
+                        SWP_NOMOVE => Some(RECT {
+                            left: cur_rect.left,
+                            top: cur_rect.top,
+                            right: cur_rect.left + window_pos.cx,
+                            bottom: cur_rect.top + window_pos.cy,
+                        }),
+
+                        SWP_NOSIZE => Some(RECT {
+                            left: window_pos.x,
+                            top: window_pos.y,
+                            right: window_pos.x - cur_rect.left + cur_rect.right,
+                            bottom: window_pos.y - cur_rect.top + cur_rect.bottom,
+                        }),
+
+                        _ => unreachable!(),
+                    }
+                } else {
+                    Some(new_rect)
+                };
+
+                if let Some(new_rect) = new_rect {
                     let new_monitor = MonitorFromRect(&new_rect, MONITOR_DEFAULTTONULL);
                     match fullscreen {
                         Fullscreen::Borderless(ref mut fullscreen_monitor) => {
@@ -989,7 +1020,8 @@ unsafe fn public_window_callback_inner<T: 'static>(
                                     .map(|monitor| new_monitor != monitor.inner.hmonitor())
                                     .unwrap_or(true)
                             {
-                            if let Ok(new_monitor_info) = monitor::get_monitor_info(new_monitor) {
+                                if let Ok(new_monitor_info) = monitor::get_monitor_info(new_monitor)
+                                {
                                     let new_monitor_rect = new_monitor_info.monitorInfo.rcMonitor;
                                     window_pos.x = new_monitor_rect.left;
                                     window_pos.y = new_monitor_rect.top;
@@ -1013,6 +1045,7 @@ unsafe fn public_window_callback_inner<T: 'static>(
                         }
                     }
                 }
+            }
 
             0
         }