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//! Utilities for working with windows on Windows.
use std::{os::windows::io::AsRawHandle, ptr, sync::Arc, thread};
use tokio::sync::broadcast;
use windows_sys::{
w,
Win32::{
Foundation::{HANDLE, HWND, LPARAM, LRESULT, WPARAM},
System::{LibraryLoader::GetModuleHandleW, Threading::GetThreadId},
UI::WindowsAndMessaging::{
CreateWindowExW, DefWindowProcW, DestroyWindow, DispatchMessageW, GetMessageW,
GetWindowLongPtrW, PostQuitMessage, PostThreadMessageW, SetWindowLongPtrW,
TranslateMessage, GWLP_USERDATA, GWLP_WNDPROC, PBT_APMRESUMEAUTOMATIC,
PBT_APMRESUMESUSPEND, PBT_APMSUSPEND, WM_DESTROY, WM_POWERBROADCAST, WM_USER,
},
},
};
const CLASS_NAME: *const u16 = w!("STATIC");
const REQUEST_THREAD_SHUTDOWN: u32 = WM_USER + 1;
/// Handle for closing an associated window.
/// The window is not destroyed when this is dropped.
pub struct WindowCloseHandle {
thread: Option<std::thread::JoinHandle<()>>,
}
impl WindowCloseHandle {
/// Close the window and wait for the thread.
pub fn close(&mut self) {
if let Some(thread) = self.thread.take() {
let thread_id = unsafe { GetThreadId(thread.as_raw_handle() as HANDLE) };
unsafe { PostThreadMessageW(thread_id, REQUEST_THREAD_SHUTDOWN, 0, 0) };
let _ = thread.join();
}
}
}
/// Creates a dummy window whose messages are handled by `wnd_proc`.
pub fn create_hidden_window<F: (Fn(HWND, u32, WPARAM, LPARAM) -> LRESULT) + Send + 'static>(
wnd_proc: F,
) -> WindowCloseHandle {
let join_handle = thread::spawn(move || {
let dummy_window = unsafe {
CreateWindowExW(
0,
CLASS_NAME,
ptr::null_mut(),
0,
0,
0,
0,
0,
0,
0,
GetModuleHandleW(ptr::null_mut()),
ptr::null_mut(),
)
};
// Move callback information to the heap.
// This enables us to reach the callback through a "thin pointer".
let raw_callback = Box::into_raw(Box::new(wnd_proc));
unsafe {
SetWindowLongPtrW(dummy_window, GWLP_USERDATA, raw_callback as isize);
SetWindowLongPtrW(
dummy_window,
GWLP_WNDPROC,
// Clippy does not like casting function pointers to anything but usize.
// But this is correct, since the Windows API expects a signed int for pointer.
window_procedure::<F> as usize as isize,
);
}
let mut msg = unsafe { std::mem::zeroed() };
loop {
let status = unsafe { GetMessageW(&mut msg, 0, 0, 0) };
if status < 0 {
continue;
}
if status == 0 {
break;
}
if msg.hwnd == 0 {
if msg.message == REQUEST_THREAD_SHUTDOWN {
unsafe { DestroyWindow(dummy_window) };
}
} else {
unsafe {
TranslateMessage(&msg);
DispatchMessageW(&msg);
}
}
}
// Free callback.
let _ = unsafe { Box::from_raw(raw_callback) };
});
WindowCloseHandle {
thread: Some(join_handle),
}
}
unsafe extern "system" fn window_procedure<F>(
window: HWND,
message: u32,
wparam: WPARAM,
lparam: LPARAM,
) -> LRESULT
where
F: Fn(HWND, u32, WPARAM, LPARAM) -> LRESULT,
{
if message == WM_DESTROY {
PostQuitMessage(0);
return 0;
}
let raw_callback = GetWindowLongPtrW(window, GWLP_USERDATA);
if raw_callback != 0 {
let typed_callback = &mut *(raw_callback as *mut F);
return typed_callback(window, message, wparam, lparam);
}
DefWindowProcW(window, message, wparam, lparam)
}
/// Power management events
#[non_exhaustive]
#[derive(Debug, Clone, Copy)]
pub enum PowerManagementEvent {
/// The system is resuming from sleep or hibernation
/// irrespective of user activity.
ResumeAutomatic,
/// The system is resuming from sleep or hibernation
/// due to user activity.
ResumeSuspend,
/// The computer is about to enter a suspended state.
Suspend,
}
impl PowerManagementEvent {
fn try_from_winevent(wparam: usize) -> Option<Self> {
use PowerManagementEvent::*;
match wparam as u32 {
PBT_APMRESUMEAUTOMATIC => Some(ResumeAutomatic),
PBT_APMRESUMESUSPEND => Some(ResumeSuspend),
PBT_APMSUSPEND => Some(Suspend),
_ => None,
}
}
}
/// Provides power management events to listeners
pub struct PowerManagementListener {
_window: Arc<WindowScopedHandle>,
rx: broadcast::Receiver<PowerManagementEvent>,
}
impl PowerManagementListener {
/// Creates a new listener. This is expensive compared to cloning an existing instance.
pub fn new() -> Self {
let (tx, rx) = tokio::sync::broadcast::channel(16);
let power_broadcast_callback = move |window, message, wparam, lparam| {
if message == WM_POWERBROADCAST {
if let Some(event) = PowerManagementEvent::try_from_winevent(wparam) {
if tx.send(event).is_err() {
log::error!("Stopping power management event monitor");
unsafe { PostQuitMessage(0) };
return 0;
}
}
}
unsafe { DefWindowProcW(window, message, wparam, lparam) }
};
let window = create_hidden_window(power_broadcast_callback);
Self {
_window: Arc::new(WindowScopedHandle(window)),
rx,
}
}
/// Returns the next power event.
pub async fn next(&mut self) -> Option<PowerManagementEvent> {
loop {
match self.rx.recv().await {
Ok(event) => break Some(event),
Err(broadcast::error::RecvError::Closed) => {
log::error!("Sender was unexpectedly dropped");
break None;
}
Err(broadcast::error::RecvError::Lagged(num_skipped)) => {
log::warn!("Skipped {num_skipped} power broadcast events");
}
}
}
}
}
impl Default for PowerManagementListener {
fn default() -> Self {
Self::new()
}
}
impl Clone for PowerManagementListener {
fn clone(&self) -> Self {
Self {
_window: self._window.clone(),
rx: self.rx.resubscribe(),
}
}
}
struct WindowScopedHandle(WindowCloseHandle);
impl Drop for WindowScopedHandle {
fn drop(&mut self) {
self.0.close();
}
}
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