windows: Remove the use of DispatcherQueue and fix FileSaveDialog unresponsive issue (#17946)

Closes #17069, closes #12410


With the help of @kennykerr (Creator of C++/WinRT and the crate
`windows-rs`, Engineer on the Windows team at Microsoft) and @riverar
(Windows Development expert), we discovered that this bug only occurs
when an IME with a candidate window, such as Microsoft Pinyin IME, is
active. In this case, the `FileSaveDialog` becomes unresponsive—while
the dialog itself appears to be functioning, it doesn't accept any mouse
or keyboard input.

After a period of debugging and testing, I found that this issue only
arises when using `DispatcherQueue` to dispatch runnables on the UI
thread. After @kennykerr’s further investigation, Kenny identified that
this is a bug with `DispatcherQueue`, and he recommended to avoid using
`DispatcherQueue`. Given the uncertainty about whether Microsoft will
address this bug in the foreseeable future, I have removed the use of
`DispatcherQueue`.

Co-authored-by: Kenny <kenny@kennykerr.ca>

Release Notes:

- N/A

---------

Co-authored-by: Kenny <kenny@kennykerr.ca>

Cargo.toml

@@ -490,7 +490,6 @@ features = [
     "implement",
     "Foundation_Numerics",
     "Storage",
-    "System",
     "System_Threading",
     "UI_ViewManagement",
     "Wdk_System_SystemServices",
@@ -521,6 +520,7 @@ features = [
     "Win32_UI_Input_Ime",
     "Win32_UI_Input_KeyboardAndMouse",
     "Win32_UI_Shell",
+    "Win32_UI_Shell_Common",
     "Win32_UI_WindowsAndMessaging",
 ]
 

crates/gpui/Cargo.toml

@@ -50,7 +50,7 @@ parking = "2.0.0"
 parking_lot.workspace = true
 postage.workspace = true
 profiling.workspace = true
-rand = { optional = true, workspace = true}
+rand = { optional = true, workspace = true }
 raw-window-handle = "0.6"
 refineable.workspace = true
 resvg = { version = "0.41.0", default-features = false }
@@ -110,6 +110,7 @@ blade-graphics.workspace = true
 blade-macros.workspace = true
 blade-util.workspace = true
 bytemuck = "1"
+flume = "0.11"
 
 [target.'cfg(target_os = "linux")'.dependencies]
 as-raw-xcb-connection = "1"
@@ -117,7 +118,6 @@ ashpd.workspace = true
 calloop = "0.13.0"
 calloop-wayland-source = "0.3.0"
 cosmic-text = { git = "https://github.com/pop-os/cosmic-text", rev = "542b20c" }
-flume = "0.11"
 wayland-backend = { version = "0.3.3", features = ["client_system", "dlopen"] }
 wayland-client = { version = "0.31.2" }
 wayland-cursor = "0.31.1"

crates/gpui/src/platform/windows/dispatcher.rs

@@ -3,51 +3,39 @@ use std::{
     time::Duration,
 };
 
+use anyhow::Context;
 use async_task::Runnable;
+use flume::Sender;
 use parking::Parker;
 use parking_lot::Mutex;
 use util::ResultExt;
 use windows::{
     Foundation::TimeSpan,
-    System::{
-        DispatcherQueue, DispatcherQueueController, DispatcherQueueHandler,
-        Threading::{
-            ThreadPool, ThreadPoolTimer, TimerElapsedHandler, WorkItemHandler, WorkItemOptions,
-            WorkItemPriority,
-        },
-    },
-    Win32::System::WinRT::{
-        CreateDispatcherQueueController, DispatcherQueueOptions, DQTAT_COM_NONE,
-        DQTYPE_THREAD_CURRENT,
+    System::Threading::{
+        ThreadPool, ThreadPoolTimer, TimerElapsedHandler, WorkItemHandler, WorkItemOptions,
+        WorkItemPriority,
     },
+    Win32::{Foundation::HANDLE, System::Threading::SetEvent},
 };
 
-use crate::{PlatformDispatcher, TaskLabel};
+use crate::{PlatformDispatcher, SafeHandle, TaskLabel};
 
 pub(crate) struct WindowsDispatcher {
-    controller: DispatcherQueueController,
-    main_queue: DispatcherQueue,
+    main_sender: Sender<Runnable>,
+    dispatch_event: SafeHandle,
     parker: Mutex<Parker>,
     main_thread_id: ThreadId,
 }
 
 impl WindowsDispatcher {
-    pub(crate) fn new() -> Self {
-        let controller = unsafe {
-            let options = DispatcherQueueOptions {
-                dwSize: std::mem::size_of::<DispatcherQueueOptions>() as u32,
-                threadType: DQTYPE_THREAD_CURRENT,
-                apartmentType: DQTAT_COM_NONE,
-            };
-            CreateDispatcherQueueController(options).unwrap()
-        };
-        let main_queue = controller.DispatcherQueue().unwrap();
+    pub(crate) fn new(main_sender: Sender<Runnable>, dispatch_event: HANDLE) -> Self {
+        let dispatch_event = dispatch_event.into();
         let parker = Mutex::new(Parker::new());
         let main_thread_id = current().id();
 
         WindowsDispatcher {
-            controller,
-            main_queue,
+            main_sender,
+            dispatch_event,
             parker,
             main_thread_id,
         }
@@ -86,12 +74,6 @@ impl WindowsDispatcher {
     }
 }
 
-impl Drop for WindowsDispatcher {
-    fn drop(&mut self) {
-        self.controller.ShutdownQueueAsync().log_err();
-    }
-}
-
 impl PlatformDispatcher for WindowsDispatcher {
     fn is_main_thread(&self) -> bool {
         current().id() == self.main_thread_id
@@ -105,14 +87,11 @@ impl PlatformDispatcher for WindowsDispatcher {
     }
 
     fn dispatch_on_main_thread(&self, runnable: Runnable) {
-        let handler = {
-            let mut task_wrapper = Some(runnable);
-            DispatcherQueueHandler::new(move || {
-                task_wrapper.take().unwrap().run();
-                Ok(())
-            })
-        };
-        self.main_queue.TryEnqueue(&handler).log_err();
+        self.main_sender
+            .send(runnable)
+            .context("Dispatch on main thread failed")
+            .log_err();
+        unsafe { SetEvent(*self.dispatch_event).log_err() };
     }
 
     fn dispatch_after(&self, duration: Duration, runnable: Runnable) {

crates/gpui/src/platform/windows/events.rs

@@ -177,6 +177,9 @@ fn handle_timer_msg(
     state_ptr: Rc<WindowsWindowStatePtr>,
 ) -> Option<isize> {
     if wparam.0 == SIZE_MOVE_LOOP_TIMER_ID {
+        for runnable in state_ptr.main_receiver.drain() {
+            runnable.run();
+        }
         handle_paint_msg(handle, state_ptr)
     } else {
         None

crates/gpui/src/platform/windows/platform.rs

@@ -8,6 +8,7 @@ use std::{
 
 use ::util::ResultExt;
 use anyhow::{anyhow, Context, Result};
+use async_task::Runnable;
 use futures::channel::oneshot::{self, Receiver};
 use itertools::Itertools;
 use parking_lot::RwLock;
@@ -46,6 +47,8 @@ pub(crate) struct WindowsPlatform {
     raw_window_handles: RwLock<SmallVec<[HWND; 4]>>,
     // The below members will never change throughout the entire lifecycle of the app.
     icon: HICON,
+    main_receiver: flume::Receiver<Runnable>,
+    dispatch_event: HANDLE,
     background_executor: BackgroundExecutor,
     foreground_executor: ForegroundExecutor,
     text_system: Arc<DirectWriteTextSystem>,
@@ -89,7 +92,9 @@ impl WindowsPlatform {
         unsafe {
             OleInitialize(None).expect("unable to initialize Windows OLE");
         }
-        let dispatcher = Arc::new(WindowsDispatcher::new());
+        let (main_sender, main_receiver) = flume::unbounded::<Runnable>();
+        let dispatch_event = unsafe { CreateEventW(None, false, false, None) }.unwrap();
+        let dispatcher = Arc::new(WindowsDispatcher::new(main_sender, dispatch_event));
         let background_executor = BackgroundExecutor::new(dispatcher.clone());
         let foreground_executor = ForegroundExecutor::new(dispatcher);
         let bitmap_factory = ManuallyDrop::new(unsafe {
@@ -113,6 +118,8 @@ impl WindowsPlatform {
             state,
             raw_window_handles,
             icon,
+            main_receiver,
+            dispatch_event,
             background_executor,
             foreground_executor,
             text_system,
@@ -176,6 +183,24 @@ impl WindowsPlatform {
 
         lock.is_empty()
     }
+
+    #[inline]
+    fn run_foreground_tasks(&self) {
+        for runnable in self.main_receiver.drain() {
+            runnable.run();
+        }
+    }
+
+    fn generate_creation_info(&self) -> WindowCreationInfo {
+        WindowCreationInfo {
+            icon: self.icon,
+            executor: self.foreground_executor.clone(),
+            current_cursor: self.state.borrow().current_cursor,
+            windows_version: self.windows_version,
+            validation_number: self.validation_number,
+            main_receiver: self.main_receiver.clone(),
+        }
+    }
 }
 
 impl Platform for WindowsPlatform {
@@ -197,16 +222,21 @@ impl Platform for WindowsPlatform {
         begin_vsync(*vsync_event);
         'a: loop {
             let wait_result = unsafe {
-                MsgWaitForMultipleObjects(Some(&[*vsync_event]), false, INFINITE, QS_ALLINPUT)
+                MsgWaitForMultipleObjects(
+                    Some(&[*vsync_event, self.dispatch_event]),
+                    false,
+                    INFINITE,
+                    QS_ALLINPUT,
+                )
             };
 
             match wait_result {
                 // compositor clock ticked so we should draw a frame
-                WAIT_EVENT(0) => {
-                    self.redraw_all();
-                }
+                WAIT_EVENT(0) => self.redraw_all(),
+                // foreground tasks are dispatched
+                WAIT_EVENT(1) => self.run_foreground_tasks(),
                 // Windows thread messages are posted
-                WAIT_EVENT(1) => {
+                WAIT_EVENT(2) => {
                     let mut msg = MSG::default();
                     unsafe {
                         while PeekMessageW(&mut msg, None, 0, 0, PM_REMOVE).as_bool() {
@@ -230,6 +260,8 @@ impl Platform for WindowsPlatform {
                             }
                         }
                     }
+                    // foreground tasks may have been queued in the message handlers
+                    self.run_foreground_tasks();
                 }
                 _ => {
                     log::error!("Something went wrong while waiting {:?}", wait_result);
@@ -319,17 +351,7 @@ impl Platform for WindowsPlatform {
         handle: AnyWindowHandle,
         options: WindowParams,
     ) -> Result<Box<dyn PlatformWindow>> {
-        let lock = self.state.borrow();
-        let window = WindowsWindow::new(
-            handle,
-            options,
-            self.icon,
-            self.foreground_executor.clone(),
-            lock.current_cursor,
-            self.windows_version,
-            self.validation_number,
-        )?;
-        drop(lock);
+        let window = WindowsWindow::new(handle, options, self.generate_creation_info())?;
         let handle = window.get_raw_handle();
         self.raw_window_handles.write().push(handle);
 
@@ -558,6 +580,15 @@ impl Drop for WindowsPlatform {
     }
 }
 
+pub(crate) struct WindowCreationInfo {
+    pub(crate) icon: HICON,
+    pub(crate) executor: ForegroundExecutor,
+    pub(crate) current_cursor: HCURSOR,
+    pub(crate) windows_version: WindowsVersion,
+    pub(crate) validation_number: usize,
+    pub(crate) main_receiver: flume::Receiver<Runnable>,
+}
+
 fn open_target(target: &str) {
     unsafe {
         let ret = ShellExecuteW(
@@ -631,22 +662,33 @@ fn file_open_dialog(options: PathPromptOptions) -> Result<Option<Vec<PathBuf>>>
 
 fn file_save_dialog(directory: PathBuf) -> Result<Option<PathBuf>> {
     let dialog: IFileSaveDialog = unsafe { CoCreateInstance(&FileSaveDialog, None, CLSCTX_ALL)? };
-    if let Some(full_path) = directory.canonicalize().log_err() {
-        let full_path = full_path.to_string_lossy().to_string();
-        if !full_path.is_empty() {
-            let path_item: IShellItem =
-                unsafe { SHCreateItemFromParsingName(&HSTRING::from(&full_path), None)? };
-            unsafe { dialog.SetFolder(&path_item).log_err() };
+    if !directory.to_string_lossy().is_empty() {
+        if let Some(full_path) = directory.canonicalize().log_err() {
+            let full_path = full_path.to_string_lossy().to_string();
+            if !full_path.is_empty() {
+                let path_item: IShellItem =
+                    unsafe { SHCreateItemFromParsingName(&HSTRING::from(&full_path), None)? };
+                unsafe { dialog.SetFolder(&path_item).log_err() };
+            }
         }
     }
     unsafe {
+        dialog.SetFileTypes(&[Common::COMDLG_FILTERSPEC {
+            pszName: windows::core::w!("All files"),
+            pszSpec: windows::core::w!("*.*"),
+        }])?;
         if dialog.Show(None).is_err() {
             // User cancelled
             return Ok(None);
         }
     }
     let shell_item = unsafe { dialog.GetResult()? };
-    let file_path_string = unsafe { shell_item.GetDisplayName(SIGDN_FILESYSPATH)?.to_string()? };
+    let file_path_string = unsafe {
+        let pwstr = shell_item.GetDisplayName(SIGDN_FILESYSPATH)?;
+        let string = pwstr.to_string()?;
+        CoTaskMemFree(Some(pwstr.0 as _));
+        string
+    };
     Ok(Some(PathBuf::from(file_path_string)))
 }
 

crates/gpui/src/platform/windows/window.rs

@@ -12,6 +12,7 @@ use std::{
 
 use ::util::ResultExt;
 use anyhow::{Context, Result};
+use async_task::Runnable;
 use futures::channel::oneshot::{self, Receiver};
 use itertools::Itertools;
 use raw_window_handle as rwh;
@@ -63,6 +64,7 @@ pub(crate) struct WindowsWindowStatePtr {
     pub(crate) executor: ForegroundExecutor,
     pub(crate) windows_version: WindowsVersion,
     pub(crate) validation_number: usize,
+    pub(crate) main_receiver: flume::Receiver<Runnable>,
 }
 
 impl WindowsWindowState {
@@ -226,6 +228,7 @@ impl WindowsWindowStatePtr {
             executor: context.executor.clone(),
             windows_version: context.windows_version,
             validation_number: context.validation_number,
+            main_receiver: context.main_receiver.clone(),
         }))
     }
 }
@@ -253,18 +256,23 @@ struct WindowCreateContext {
     current_cursor: HCURSOR,
     windows_version: WindowsVersion,
     validation_number: usize,
+    main_receiver: flume::Receiver<Runnable>,
 }
 
 impl WindowsWindow {
     pub(crate) fn new(
         handle: AnyWindowHandle,
         params: WindowParams,
-        icon: HICON,
-        executor: ForegroundExecutor,
-        current_cursor: HCURSOR,
-        windows_version: WindowsVersion,
-        validation_number: usize,
+        creation_info: WindowCreationInfo,
     ) -> Result<Self> {
+        let WindowCreationInfo {
+            icon,
+            executor,
+            current_cursor,
+            windows_version,
+            validation_number,
+            main_receiver,
+        } = creation_info;
         let classname = register_wnd_class(icon);
         let hide_title_bar = params
             .titlebar
@@ -305,6 +313,7 @@ impl WindowsWindow {
             current_cursor,
             windows_version,
             validation_number,
+            main_receiver,
         };
         let lpparam = Some(&context as *const _ as *const _);
         let creation_result = unsafe {