On Windows, add opt-in function for device events (#2409)

CHANGELOG.md

@@ -11,6 +11,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On macOS, fixed touch phase reporting when scrolling.
 - On X11, fix min, max and resize increment hints not persisting for resizable windows (e.g. on DPI change).
 - On Windows, respect min/max inner sizes when creating the window.
+- **Breaking:** On Windows, device events are now ignored for unfocused windows by default, use `EventLoopWindowTarget::set_device_event_filter` to set the filter level.
 
 # 0.27.1 (2022-07-30)
 

src/event_loop.rs

@@ -323,7 +323,7 @@ impl<T> EventLoopWindowTarget<T> {
     ///
     /// ## Platform-specific
     ///
-    /// - **Wayland / Windows / macOS / iOS / Android / Web:** Unsupported.
+    /// - **Wayland / macOS / iOS / Android / Web:** Unsupported.
     ///
     /// [`DeviceEvent`]: crate::event::DeviceEvent
     pub fn set_device_event_filter(&self, _filter: DeviceEventFilter) {
@@ -332,7 +332,8 @@ impl<T> EventLoopWindowTarget<T> {
             target_os = "dragonfly",
             target_os = "freebsd",
             target_os = "netbsd",
-            target_os = "openbsd"
+            target_os = "openbsd",
+            target_os = "windows"
         ))]
         self.p.set_device_event_filter(_filter);
     }

src/platform_impl/windows/event_loop.rs

@@ -77,7 +77,9 @@ use windows_sys::Win32::{
 use crate::{
     dpi::{PhysicalPosition, PhysicalSize},
     event::{DeviceEvent, Event, Force, Ime, KeyboardInput, Touch, TouchPhase, WindowEvent},
-    event_loop::{ControlFlow, EventLoopClosed, EventLoopWindowTarget as RootELW},
+    event_loop::{
+        ControlFlow, DeviceEventFilter, EventLoopClosed, EventLoopWindowTarget as RootELW,
+    },
     monitor::MonitorHandle as RootMonitorHandle,
     platform_impl::platform::{
         dark_mode::try_theme,
@@ -207,7 +209,10 @@ impl<T: 'static> EventLoop<T> {
 
         let thread_msg_sender =
             insert_event_target_window_data::<T>(thread_msg_target, runner_shared.clone());
-        raw_input::register_all_mice_and_keyboards_for_raw_input(thread_msg_target);
+        raw_input::register_all_mice_and_keyboards_for_raw_input(
+            thread_msg_target,
+            Default::default(),
+        );
 
         EventLoop {
             thread_msg_sender,
@@ -322,6 +327,10 @@ impl<T> EventLoopWindowTarget<T> {
     pub fn raw_display_handle(&self) -> RawDisplayHandle {
         RawDisplayHandle::Windows(WindowsDisplayHandle::empty())
     }
+
+    pub fn set_device_event_filter(&self, filter: DeviceEventFilter) {
+        raw_input::register_all_mice_and_keyboards_for_raw_input(self.thread_msg_target, filter);
+    }
 }
 
 /// Returns the id of the main thread.

src/platform_impl/windows/raw_input.rs

@@ -12,9 +12,9 @@ use windows_sys::Win32::{
         Input::{
             GetRawInputData, GetRawInputDeviceInfoW, GetRawInputDeviceList,
             RegisterRawInputDevices, HRAWINPUT, RAWINPUT, RAWINPUTDEVICE, RAWINPUTDEVICELIST,
-            RAWINPUTHEADER, RIDEV_DEVNOTIFY, RIDEV_INPUTSINK, RIDI_DEVICEINFO, RIDI_DEVICENAME,
-            RID_DEVICE_INFO, RID_DEVICE_INFO_HID, RID_DEVICE_INFO_KEYBOARD, RID_DEVICE_INFO_MOUSE,
-            RID_INPUT, RIM_TYPEHID, RIM_TYPEKEYBOARD, RIM_TYPEMOUSE,
+            RAWINPUTHEADER, RIDEV_DEVNOTIFY, RIDEV_INPUTSINK, RIDEV_REMOVE, RIDI_DEVICEINFO,
+            RIDI_DEVICENAME, RID_DEVICE_INFO, RID_DEVICE_INFO_HID, RID_DEVICE_INFO_KEYBOARD,
+            RID_DEVICE_INFO_MOUSE, RID_INPUT, RIM_TYPEHID, RIM_TYPEKEYBOARD, RIM_TYPEMOUSE,
         },
         WindowsAndMessaging::{
             RI_MOUSE_LEFT_BUTTON_DOWN, RI_MOUSE_LEFT_BUTTON_UP, RI_MOUSE_MIDDLE_BUTTON_DOWN,
@@ -23,7 +23,7 @@ use windows_sys::Win32::{
     },
 };
 
-use crate::{event::ElementState, platform_impl::platform::util};
+use crate::{event::ElementState, event_loop::DeviceEventFilter, platform_impl::platform::util};
 
 #[allow(dead_code)]
 pub fn get_raw_input_device_list() -> Option<Vec<RAWINPUTDEVICELIST>> {
@@ -138,10 +138,21 @@ pub fn register_raw_input_devices(devices: &[RAWINPUTDEVICE]) -> bool {
     }
 }
 
-pub fn register_all_mice_and_keyboards_for_raw_input(window_handle: HWND) -> bool {
+pub fn register_all_mice_and_keyboards_for_raw_input(
+    mut window_handle: HWND,
+    filter: DeviceEventFilter,
+) -> bool {
     // RIDEV_DEVNOTIFY: receive hotplug events
     // RIDEV_INPUTSINK: receive events even if we're not in the foreground
-    let flags = RIDEV_DEVNOTIFY | RIDEV_INPUTSINK;
+    // RIDEV_REMOVE: don't receive device events (requires NULL hwndTarget)
+    let flags = match filter {
+        DeviceEventFilter::Always => {
+            window_handle = 0;
+            RIDEV_REMOVE
+        }
+        DeviceEventFilter::Unfocused => RIDEV_DEVNOTIFY,
+        DeviceEventFilter::Never => RIDEV_DEVNOTIFY | RIDEV_INPUTSINK,
+    };
 
     let devices: [RAWINPUTDEVICE; 2] = [
         RAWINPUTDEVICE {