Improve fullscreen window monitor switching on Windows

CHANGELOG.md

@@ -23,6 +23,8 @@
 - On Wayland, add support for set_cursor_visible and set_cursor_grab.
 - On Wayland, fixed DeviceEvents for relative mouse movement is not always produced
 - On Wayland, add support for set_cursor_icon.
+- On Windows, disable monitor change keyboard shortcut while in exclusive fullscreen.
+- On Windows, ensure that changing a borderless fullscreen window's monitor via keyboard shortcuts keeps the window fullscreen on the new monitor.
 
 # 0.20.0 Alpha 3 (2019-08-14)
 

src/platform_impl/windows/event_loop.rs

@@ -54,13 +54,14 @@ use crate::{
         },
         drop_handler::FileDropHandler,
         event::{self, handle_extended_keys, process_key_params, vkey_to_winit_vkey},
+        monitor,
         raw_input::{get_raw_input_data, get_raw_mouse_button_state},
         util,
         window::adjust_size,
         window_state::{CursorFlags, WindowFlags, WindowState},
         wrap_device_id, WindowId, DEVICE_ID,
     },
-    window::WindowId as RootWindowId,
+    window::{WindowId as RootWindowId, Fullscreen},
 };
 
 type GetPointerFrameInfoHistory = unsafe extern "system" fn(
@@ -982,6 +983,48 @@ unsafe extern "system" fn public_window_callback<T>(
             commctrl::DefSubclassProc(window, msg, wparam, lparam)
         }
 
+        winuser::WM_WINDOWPOSCHANGING => {
+            let mut window_state = subclass_input.window_state.lock();
+            if let Some(ref mut fullscreen) = window_state.fullscreen {
+                let window_pos = &mut *(lparam as *mut winuser::WINDOWPOS);
+                let new_rect = RECT {
+                    left: window_pos.x,
+                    top: window_pos.y,
+                    right: window_pos.x + window_pos.cx,
+                    bottom: window_pos.y + window_pos.cy,
+                };
+                let new_monitor = winuser::MonitorFromRect(&new_rect, winuser::MONITOR_DEFAULTTONULL);
+                match fullscreen {
+                    Fullscreen::Borderless(ref mut fullscreen_monitor) => {
+                        if new_monitor != fullscreen_monitor.inner.hmonitor() && new_monitor != ptr::null_mut() {
+                            if let Ok(new_monitor_info) = monitor::get_monitor_info(new_monitor) {
+                                let new_monitor_rect = new_monitor_info.rcMonitor;
+                                window_pos.x = new_monitor_rect.left;
+                                window_pos.y = new_monitor_rect.top;
+                                window_pos.cx = new_monitor_rect.right - new_monitor_rect.left;
+                                window_pos.cy = new_monitor_rect.bottom - new_monitor_rect.top;
+                            }
+                            *fullscreen_monitor = crate::monitor::MonitorHandle {
+                                inner: monitor::MonitorHandle::new(new_monitor)
+                            };
+                        }
+                    },
+                    Fullscreen::Exclusive(ref video_mode) => {
+                        let old_monitor = video_mode.video_mode.monitor.hmonitor();
+                        if let Ok(old_monitor_info) = monitor::get_monitor_info(old_monitor) {
+                            let old_monitor_rect = old_monitor_info.rcMonitor;
+                            window_pos.x = old_monitor_rect.left;
+                            window_pos.y = old_monitor_rect.top;
+                            window_pos.cx = old_monitor_rect.right - old_monitor_rect.left;
+                            window_pos.cy = old_monitor_rect.bottom - old_monitor_rect.top;
+                        }
+                    }
+                }
+            }
+
+            0
+        }
+
         // WM_MOVE supplies client area positions, so we send Moved here instead.
         winuser::WM_WINDOWPOSCHANGED => {
             use crate::event::WindowEvent::Moved;