Merge pull request #141 from mahkoh/jorth/fifo

wayland: implement fifo-v1

docs/features.md

@@ -159,6 +159,7 @@ Jay supports the following wayland protocols:
 | wp_content_type_manager_v1                           | 1               |               |
 | wp_cursor_shape_manager_v1                           | 1               |               |
 | wp_drm_lease_device_v1                               | 1               |               |
+| wp_fifo_manager_v1                                   | 1               |               |
 | wp_fractional_scale_manager_v1                       | 1               |               |
 | wp_linux_drm_syncobj_manager_v1                      | 1               |               |
 | wp_presentation                                      | 1               |               |

release-notes.md

@@ -9,6 +9,7 @@
 - Implement ext-image-copy-capture-v1.
 - Implement screencast session restoration.
 - Fix screen sharing in zoom.
+- Implement wp-fifo-v1.
 
 # 1.6.0 (2024-09-25)
 

src/backends/metal/present.rs

@@ -168,7 +168,7 @@ impl MetalConnector {
         self.latch_cursor(&node)?;
         let cursor_programming = self.compute_cursor_programming();
         let latched = self.latch(&node);
-        node.latched();
+        node.latched(self.try_async_flip());
 
         if cursor_programming.is_none() && latched.is_none() {
             return Ok(());

src/client.rs

@@ -148,7 +148,7 @@ impl Clients {
         bounding_caps: ClientCaps,
         is_xwayland: bool,
     ) -> Result<Rc<Client>, ClientError> {
-        let data = Rc::new(Client {
+        let data = Rc::new_cyclic(|slf| Client {
             id,
             state: global.clone(),
             checking_queue_size: Cell::new(false),
@@ -171,6 +171,8 @@ impl Clients {
             commit_timelines: Rc::new(CommitTimelines::new(
                 &global.wait_for_sync_obj,
                 &global.ring,
+                &global.eng,
+                slf,
             )),
             wire_scale: Default::default(),
         });

src/compositor.rs

@@ -32,7 +32,7 @@ use {
         scale::Scale,
         sighand::{self, SighandError},
         state::{ConnectorData, IdleState, ScreenlockState, State, XWaylandState},
-        tasks::{self, idle},
+        tasks::{self, handle_const_40hz_latch, idle},
         tracy::enable_profiler,
         tree::{
             container_layout, container_render_positions, container_render_titles, float_layout,
@@ -272,6 +272,7 @@ fn start_compositor2(
         ui_drag_enabled: Cell::new(true),
         ui_drag_threshold_squared: Cell::new(10),
         toplevels: Default::default(),
+        const_40hz_latch: Default::default(),
     });
     state.tracker.register(ClientId::from_raw(0));
     create_dummy_output(&state);
@@ -435,6 +436,11 @@ fn start_global_event_handlers(
             "slow ei clients",
             tasks::handle_slow_ei_clients(state.clone()),
         ),
+        eng.spawn2(
+            "const 40hz latch",
+            Phase::Present,
+            handle_const_40hz_latch(state.clone()),
+        ),
     ]
 }
 

src/globals.rs

@@ -39,6 +39,7 @@ use {
             wp_alpha_modifier_v1::WpAlphaModifierV1Global,
             wp_content_type_manager_v1::WpContentTypeManagerV1Global,
             wp_cursor_shape_manager_v1::WpCursorShapeManagerV1Global,
+            wp_fifo_manager_v1::WpFifoManagerV1Global,
             wp_fractional_scale_manager_v1::WpFractionalScaleManagerV1Global,
             wp_presentation::WpPresentationGlobal,
             wp_security_context_manager_v1::WpSecurityContextManagerV1Global,
@@ -203,6 +204,7 @@ impl Globals {
         add_singleton!(ExtOutputImageCaptureSourceManagerV1Global);
         add_singleton!(ExtForeignToplevelImageCaptureSourceManagerV1Global);
         add_singleton!(ExtImageCopyCaptureManagerV1Global);
+        add_singleton!(WpFifoManagerV1Global);
     }
 
     pub fn add_backend_singletons(&self, backend: &Rc<dyn Backend>) {

src/ifs.rs

@@ -53,6 +53,7 @@ pub mod wp_drm_lease_connector_v1;
 pub mod wp_drm_lease_device_v1;
 pub mod wp_drm_lease_request_v1;
 pub mod wp_drm_lease_v1;
+pub mod wp_fifo_manager_v1;
 pub mod wp_fractional_scale_manager_v1;
 pub mod wp_linux_drm_syncobj_manager_v1;
 pub mod wp_linux_drm_syncobj_timeline_v1;

src/ifs/ext_image_copy/ext_image_copy_capture_session_v1.rs

@@ -269,7 +269,7 @@ impl ExtImageCopyCaptureSessionV1RequestHandler for ExtImageCopyCaptureSessionV1
 }
 
 impl LatchListener for ExtImageCopyCaptureSessionV1 {
-    fn after_latch(self: Rc<Self>, on: &OutputNode) {
+    fn after_latch(self: Rc<Self>, on: &OutputNode, _tearing: bool) {
         let ImageCaptureSource::Toplevel(tl) = &self.source else {
             return;
         };

src/ifs/jay_screencast.rs

@@ -89,7 +89,7 @@ enum Target {
 }
 
 impl LatchListener for JayScreencast {
-    fn after_latch(self: Rc<Self>, _on: &OutputNode) {
+    fn after_latch(self: Rc<Self>, _on: &OutputNode, _tearing: bool) {
         self.schedule_toplevel_screencast();
     }
 }

src/ifs/wl_surface.rs

@@ -4,6 +4,7 @@ pub mod dnd_icon;
 pub mod ext_session_lock_surface_v1;
 pub mod wl_subsurface;
 pub mod wp_alpha_modifier_surface_v1;
+pub mod wp_fifo_v1;
 pub mod wp_fractional_scale_v1;
 pub mod wp_linux_drm_syncobj_surface_v1;
 pub mod wp_tearing_control_v1;
@@ -46,6 +47,7 @@ use {
                 dnd_icon::DndIcon,
                 wl_subsurface::{PendingSubsurfaceData, SubsurfaceId, WlSubsurface},
                 wp_alpha_modifier_surface_v1::WpAlphaModifierSurfaceV1,
+                wp_fifo_v1::WpFifoV1,
                 wp_fractional_scale_v1::WpFractionalScaleV1,
                 wp_linux_drm_syncobj_surface_v1::WpLinuxDrmSyncobjSurfaceV1,
                 wp_tearing_control_v1::WpTearingControlV1,
@@ -317,6 +319,8 @@ pub struct WlSurface {
     presentation_listener: EventListener<dyn PresentationListener>,
     commit_version: NumCell<u64>,
     latched_commit_version: Cell<u64>,
+    fifo: CloneCell<Option<Rc<WpFifoV1>>>,
+    clear_fifo_on_vblank: Cell<bool>,
 }
 
 impl Debug for WlSurface {
@@ -438,6 +442,8 @@ struct PendingState {
     release_point: Option<(Rc<SyncObj>, SyncObjPoint)>,
     alpha_multiplier: Option<Option<f32>>,
     explicit_sync: bool,
+    fifo_barrier_set: bool,
+    fifo_barrier_wait: bool,
 }
 
 struct AttachedSubsurfaceState {
@@ -515,6 +521,8 @@ impl PendingState {
             &mut self.presentation_feedback,
             &mut next.presentation_feedback,
         );
+        self.fifo_barrier_set |= mem::take(&mut next.fifo_barrier_set);
+        self.fifo_barrier_wait |= mem::take(&mut next.fifo_barrier_wait);
         macro_rules! merge_ext {
             ($name:ident) => {
                 if let Some(e) = &mut self.$name {
@@ -638,6 +646,8 @@ impl WlSurface {
             presentation_listener: EventListener::new(slf.clone()),
             commit_version: Default::default(),
             latched_commit_version: Default::default(),
+            fifo: Default::default(),
+            clear_fifo_on_vblank: Default::default(),
         }
     }
 
@@ -1314,14 +1324,22 @@ impl WlSurface {
             }
         }
         self.ext.get().after_apply_commit();
+        let fifo_barrier_set = mem::take(&mut pending.fifo_barrier_set);
+        if fifo_barrier_set {
+            self.commit_timeline.set_fifo_barrier();
+        }
         if self.visible.get() {
             let output = self.output.get();
             if has_frame_requests {
                 self.vblank_listener.attach(&output.vblank_event);
             }
-            if has_presentation_feedback {
+            if has_presentation_feedback || fifo_barrier_set {
                 self.latch_listener.attach(&output.latch_event);
             }
+            if fifo_barrier_set {
+                // If we have a fifo barrier, must trigger latching.
+                output.global.connector.damage();
+            }
             if damage_full {
                 let mut damage = buffer_abs_pos
                     .with_size(max_surface_size.0, max_surface_size.1)
@@ -1341,10 +1359,16 @@ impl WlSurface {
                 let rect = output.global.pos.get();
                 self.client.state.damage(rect);
             }
+        } else {
+            if fifo_barrier_set {
+                self.latch_listener
+                    .attach(&self.client.state.const_40hz_latch);
+            }
         }
         pending.buffer_damage.clear();
         pending.surface_damage.clear();
         pending.damage_full = false;
+        pending.fifo_barrier_wait = false;
         if tearing_changed {
             if let Some(tl) = self.toplevel.get() {
                 if tl.tl_data().is_fullscreen.get() {
@@ -1631,6 +1655,8 @@ impl Object for WlSurface {
         self.drm_feedback.clear();
         self.commit_timeline.clear(ClearReason::BreakLoops);
         self.alpha_modifier.take();
+        self.text_input_connections.clear();
+        self.fifo.take();
     }
 }
 
@@ -2101,12 +2127,15 @@ impl VblankListener for WlSurface {
                 let _ = fr.client.remove_obj(&*fr);
             }
         }
+        if self.clear_fifo_on_vblank.take() {
+            self.commit_timeline.clear_fifo_barrier();
+        }
         self.vblank_listener.detach();
     }
 }
 
 impl LatchListener for WlSurface {
-    fn after_latch(self: Rc<Self>, _on: &OutputNode) {
+    fn after_latch(self: Rc<Self>, _on: &OutputNode, tearing: bool) {
         if self.visible.get() {
             if self.latched_commit_version.get() < self.commit_version.get() {
                 let latched = &mut *self.latched_presentation_feedback.borrow_mut();
@@ -2122,6 +2151,14 @@ impl LatchListener for WlSurface {
                 self.latched_commit_version.set(self.commit_version.get());
             }
         }
+        if tearing && self.visible.get() {
+            if self.commit_timeline.has_fifo_barrier() {
+                self.vblank_listener.attach(&self.output.get().vblank_event);
+                self.clear_fifo_on_vblank.set(true);
+            }
+        } else {
+            self.commit_timeline.clear_fifo_barrier();
+        }
         self.latch_listener.detach();
     }
 }

src/ifs/wl_surface/commit_timeline.rs

@@ -1,5 +1,7 @@
 use {
     crate::{
+        async_engine::{AsyncEngine, SpawnedFuture},
+        client::Client,
         gfx_api::{AsyncShmGfxTextureCallback, GfxError, PendingShmTransfer, STAGING_UPLOAD},
         ifs::{
             wl_buffer::WlBufferStorage,
@@ -13,6 +15,7 @@ use {
             linkedlist::{LinkedList, LinkedNode, NodeRef},
             numcell::NumCell,
             oserror::OsError,
+            queue::AsyncQueue,
         },
         video::drm::{
             sync_obj::{SyncObj, SyncObjPoint},
@@ -26,7 +29,7 @@ use {
         cell::{Cell, RefCell},
         mem,
         ops::DerefMut,
-        rc::Rc,
+        rc::{Rc, Weak},
         slice,
     },
     thiserror::Error,
@@ -43,6 +46,8 @@ pub struct CommitTimelines {
     ring: Rc<IoUring>,
     depth: NumCell<usize>,
     gc: CopyHashMap<CommitTimelineId, LinkedList<Entry>>,
+    flush_requests: Rc<FlushRequests>,
+    _flush_requests_future: SpawnedFuture<()>,
 }
 
 pub struct CommitTimeline {
@@ -50,6 +55,8 @@ pub struct CommitTimeline {
     own_timeline: Rc<Inner>,
     effective_timeline: CloneCell<Rc<Inner>>,
     effective_timeline_id: Cell<CommitTimelineId>,
+    fifo_barrier_set: Cell<bool>,
+    fifo_waiter: Cell<Option<NodeRef<Entry>>>,
 }
 
 struct Inner {
@@ -94,8 +101,20 @@ pub enum CommitTimelineError {
 }
 
 impl CommitTimelines {
-    pub fn new(wfs: &Rc<WaitForSyncObj>, ring: &Rc<IoUring>) -> Self {
+    pub fn new(
+        wfs: &Rc<WaitForSyncObj>,
+        ring: &Rc<IoUring>,
+        eng: &Rc<AsyncEngine>,
+        client: &Weak<Client>,
+    ) -> Self {
+        let flush_requests = Rc::new(FlushRequests::default());
+        let flush_request_future = eng.spawn(
+            "wl_surface flush requests",
+            process_flush_requests(client.clone(), flush_requests.clone()),
+        );
         Self {
+            flush_requests,
+            _flush_requests_future: flush_request_future,
             next_id: Default::default(),
             depth: NumCell::new(0),
             wfs: wfs.clone(),
@@ -115,10 +134,13 @@ impl CommitTimelines {
             own_timeline: timeline.clone(),
             effective_timeline: CloneCell::new(timeline),
             effective_timeline_id: Cell::new(id),
+            fifo_barrier_set: Cell::new(false),
+            fifo_waiter: Default::default(),
         }
     }
 
     pub fn clear(&self) {
+        self.flush_requests.flush_waiters.clear();
         for list in self.gc.lock().drain_values() {
             break_loops(&list);
         }
@@ -144,8 +166,12 @@ fn break_loops(list: &LinkedList<Entry>) {
 impl CommitTimeline {
     pub fn clear(&self, reason: ClearReason) {
         match reason {
-            ClearReason::BreakLoops => break_loops(&self.own_timeline.entries),
+            ClearReason::BreakLoops => {
+                self.fifo_waiter.take();
+                break_loops(&self.own_timeline.entries)
+            }
             ClearReason::Destroy => {
+                self.clear_fifo_barrier();
                 if self.own_timeline.entries.is_not_empty() {
                     let list = LinkedList::new();
                     list.append_all(&self.own_timeline.entries);
@@ -172,7 +198,10 @@ impl CommitTimeline {
         );
         let has_dependencies =
             points.is_not_empty() || pending_uploads > 0 || implicit_dmabufs.is_not_empty();
-        if !has_dependencies && self.own_timeline.entries.is_empty() {
+        let must_be_queued = has_dependencies
+            || self.own_timeline.entries.is_not_empty()
+            || (pending.fifo_barrier_wait && self.fifo_barrier_set.get());
+        if !must_be_queued {
             return surface
                 .apply_state(pending)
                 .map_err(CommitTimelineError::ImmediateCommit);
@@ -181,6 +210,10 @@ impl CommitTimeline {
             return Err(CommitTimelineError::Depth);
         }
         set_effective_timeline(self, pending, &self.own_timeline);
+        let commit_fifo_state = match pending.fifo_barrier_wait {
+            true => CommitFifoState::Queued,
+            false => CommitFifoState::Mailbox,
+        };
         let noderef = add_entry(
             &self.own_timeline.entries,
             &self.shared,
@@ -193,9 +226,10 @@ impl CommitTimeline {
                 shm_upload: RefCell::new(ShmUploadState::None),
                 num_pending_polls: NumCell::new(implicit_dmabufs.len()),
                 pending_polls: Cell::new(Default::default()),
+                fifo_state: Cell::new(commit_fifo_state),
             }),
         );
-        let mut needs_flush = false;
+        let mut needs_flush = commit_fifo_state == CommitFifoState::Queued;
         if has_dependencies {
             let noderef = Rc::new(noderef.clone());
             let EntryKind::Commit(commit) = &noderef.kind else {
@@ -235,6 +269,21 @@ impl CommitTimeline {
         }
         Ok(())
     }
+
+    pub fn set_fifo_barrier(&self) {
+        self.fifo_barrier_set.set(true);
+    }
+
+    pub fn clear_fifo_barrier(&self) {
+        self.fifo_barrier_set.set(false);
+        if let Some(waiter) = self.fifo_waiter.take() {
+            self.shared.flush_requests.flush_waiters.push(waiter);
+        }
+    }
+
+    pub fn has_fifo_barrier(&self) -> bool {
+        self.fifo_barrier_set.get()
+    }
 }
 
 impl SyncObjWaiter for NodeRef<Entry> {
@@ -322,6 +371,7 @@ struct Commit {
     shm_upload: RefCell<ShmUploadState>,
     num_pending_polls: NumCell<usize>,
     pending_polls: Cell<SmallVec<[PendingPoll; 1]>>,
+    fifo_state: Cell<CommitFifoState>,
 }
 
 fn flush_from(mut point: NodeRef<Entry>) -> Result<(), WlSurfaceError> {
@@ -357,6 +407,20 @@ impl NodeRef<Entry> {
                 if c.num_pending_polls.get() > 0 {
                     has_unmet_dependencies = true;
                 }
+                let tl = &c.surface.commit_timeline;
+                if tl.fifo_barrier_set.get() {
+                    match c.fifo_state.get() {
+                        CommitFifoState::Queued => {
+                            tl.fifo_waiter.set(Some(self.clone()));
+                            c.fifo_state.set(CommitFifoState::Registered);
+                            has_unmet_dependencies = true;
+                        }
+                        CommitFifoState::Registered => {
+                            has_unmet_dependencies = true;
+                        }
+                        CommitFifoState::Mailbox => {}
+                    }
+                }
                 if has_unmet_dependencies {
                     return Ok(false);
                 }
@@ -536,3 +600,29 @@ fn set_effective_timeline(
         }
     }
 }
+
+#[derive(Default)]
+struct FlushRequests {
+    flush_waiters: AsyncQueue<NodeRef<Entry>>,
+}
+
+async fn process_flush_requests(client: Weak<Client>, requests: Rc<FlushRequests>) {
+    loop {
+        requests.flush_waiters.non_empty().await;
+        while let Some(entry) = requests.flush_waiters.try_pop() {
+            if let Err(e) = flush_from(entry) {
+                if let Some(client) = client.upgrade() {
+                    client.error(e);
+                }
+                return;
+            }
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+enum CommitFifoState {
+    Queued,
+    Registered,
+    Mailbox,
+}

src/ifs/wl_surface/wp_fifo_v1.rs

@@ -0,0 +1,77 @@
+use {
+    crate::{
+        client::{Client, ClientError},
+        ifs::wl_surface::WlSurface,
+        leaks::Tracker,
+        object::{Object, Version},
+        wire::{wp_fifo_v1::*, WpFifoV1Id},
+    },
+    std::rc::Rc,
+    thiserror::Error,
+};
+
+pub struct WpFifoV1 {
+    pub id: WpFifoV1Id,
+    pub client: Rc<Client>,
+    pub surface: Rc<WlSurface>,
+    pub tracker: Tracker<Self>,
+    pub version: Version,
+}
+
+impl WpFifoV1 {
+    pub fn new(id: WpFifoV1Id, version: Version, surface: &Rc<WlSurface>) -> Self {
+        Self {
+            id,
+            client: surface.client.clone(),
+            surface: surface.clone(),
+            tracker: Default::default(),
+            version,
+        }
+    }
+
+    pub fn install(self: &Rc<Self>) -> Result<(), WpFifoV1Error> {
+        if self.surface.fifo.is_some() {
+            return Err(WpFifoV1Error::Exists);
+        }
+        self.surface.fifo.set(Some(self.clone()));
+        Ok(())
+    }
+}
+
+impl WpFifoV1RequestHandler for WpFifoV1 {
+    type Error = WpFifoV1Error;
+
+    fn set_barrier(&self, _req: SetBarrier, _slf: &Rc<Self>) -> Result<(), Self::Error> {
+        self.surface.pending.borrow_mut().fifo_barrier_set = true;
+        Ok(())
+    }
+
+    fn wait_barrier(&self, _req: WaitBarrier, _slf: &Rc<Self>) -> Result<(), Self::Error> {
+        self.surface.pending.borrow_mut().fifo_barrier_wait = true;
+        Ok(())
+    }
+
+    fn destroy(&self, _req: Destroy, _slf: &Rc<Self>) -> Result<(), Self::Error> {
+        self.surface.fifo.take();
+        self.client.remove_obj(self)?;
+        Ok(())
+    }
+}
+
+object_base! {
+    self = WpFifoV1;
+    version = self.version;
+}
+
+impl Object for WpFifoV1 {}
+
+simple_add_obj!(WpFifoV1);
+
+#[derive(Debug, Error)]
+pub enum WpFifoV1Error {
+    #[error(transparent)]
+    ClientError(Box<ClientError>),
+    #[error("The surface already has a fifo extension attached")]
+    Exists,
+}
+efrom!(WpFifoV1Error, ClientError);

src/ifs/wp_fifo_manager_v1.rs

@@ -0,0 +1,96 @@
+use {
+    crate::{
+        client::{Client, ClientError},
+        globals::{Global, GlobalName},
+        ifs::wl_surface::wp_fifo_v1::{WpFifoV1, WpFifoV1Error},
+        leaks::Tracker,
+        object::{Object, Version},
+        wire::{wp_fifo_manager_v1::*, WpFifoManagerV1Id},
+    },
+    std::rc::Rc,
+    thiserror::Error,
+};
+
+pub struct WpFifoManagerV1Global {
+    pub name: GlobalName,
+}
+
+pub struct WpFifoManagerV1 {
+    pub id: WpFifoManagerV1Id,
+    pub client: Rc<Client>,
+    pub tracker: Tracker<Self>,
+    pub version: Version,
+}
+
+impl WpFifoManagerV1Global {
+    pub fn new(name: GlobalName) -> Self {
+        Self { name }
+    }
+
+    fn bind_(
+        self: Rc<Self>,
+        id: WpFifoManagerV1Id,
+        client: &Rc<Client>,
+        version: Version,
+    ) -> Result<(), WpFifoManagerV1Error> {
+        let obj = Rc::new(WpFifoManagerV1 {
+            id,
+            client: client.clone(),
+            tracker: Default::default(),
+            version,
+        });
+        track!(client, obj);
+        client.add_client_obj(&obj)?;
+        Ok(())
+    }
+}
+
+global_base!(WpFifoManagerV1Global, WpFifoManagerV1, WpFifoManagerV1Error);
+
+impl Global for WpFifoManagerV1Global {
+    fn singleton(&self) -> bool {
+        true
+    }
+
+    fn version(&self) -> u32 {
+        1
+    }
+}
+
+simple_add_global!(WpFifoManagerV1Global);
+
+impl WpFifoManagerV1RequestHandler for WpFifoManagerV1 {
+    type Error = WpFifoManagerV1Error;
+
+    fn destroy(&self, _req: Destroy, _slf: &Rc<Self>) -> Result<(), Self::Error> {
+        self.client.remove_obj(self)?;
+        Ok(())
+    }
+
+    fn get_fifo(&self, req: GetFifo, _slf: &Rc<Self>) -> Result<(), Self::Error> {
+        let surface = self.client.lookup(req.surface)?;
+        let fs = Rc::new(WpFifoV1::new(req.id, self.version, &surface));
+        track!(self.client, fs);
+        fs.install()?;
+        self.client.add_client_obj(&fs)?;
+        Ok(())
+    }
+}
+
+object_base! {
+    self = WpFifoManagerV1;
+    version = self.version;
+}
+
+impl Object for WpFifoManagerV1 {}
+
+simple_add_obj!(WpFifoManagerV1);
+
+#[derive(Debug, Error)]
+pub enum WpFifoManagerV1Error {
+    #[error(transparent)]
+    ClientError(Box<ClientError>),
+    #[error(transparent)]
+    WpFifoV1Error(#[from] WpFifoV1Error),
+}
+efrom!(WpFifoManagerV1Error, ClientError);

src/state.rs

@@ -69,16 +69,16 @@ use {
         theme::{Color, Theme},
         time::Time,
         tree::{
-            ContainerNode, ContainerSplit, Direction, DisplayNode, FloatNode, Node, NodeIds,
-            NodeVisitorBase, OutputNode, PlaceholderNode, TearingMode, ToplevelNode,
+            ContainerNode, ContainerSplit, Direction, DisplayNode, FloatNode, LatchListener, Node,
+            NodeIds, NodeVisitorBase, OutputNode, PlaceholderNode, TearingMode, ToplevelNode,
             ToplevelNodeBase, VrrMode, WorkspaceNode,
         },
         utils::{
             activation_token::ActivationToken, asyncevent::AsyncEvent, bindings::Bindings,
-            clonecell::CloneCell, copyhashmap::CopyHashMap, errorfmt::ErrorFmt, fdcloser::FdCloser,
-            hash_map_ext::HashMapExt, linkedlist::LinkedList, numcell::NumCell, queue::AsyncQueue,
-            refcounted::RefCounted, run_toplevel::RunToplevel,
-            toplevel_identifier::ToplevelIdentifier,
+            clonecell::CloneCell, copyhashmap::CopyHashMap, errorfmt::ErrorFmt,
+            event_listener::EventSource, fdcloser::FdCloser, hash_map_ext::HashMapExt,
+            linkedlist::LinkedList, numcell::NumCell, queue::AsyncQueue, refcounted::RefCounted,
+            run_toplevel::RunToplevel, toplevel_identifier::ToplevelIdentifier,
         },
         video::{
             dmabuf::DmaBufIds,
@@ -222,6 +222,7 @@ pub struct State {
     pub ui_drag_enabled: Cell<bool>,
     pub ui_drag_threshold_squared: Cell<i32>,
     pub toplevels: CopyHashMap<ToplevelIdentifier, Weak<dyn ToplevelNode>>,
+    pub const_40hz_latch: EventSource<dyn LatchListener>,
 }
 
 // impl Drop for State {
@@ -938,7 +939,7 @@ impl State {
             output.global.persistent.scale.get(),
             render_hw_cursor,
         )?;
-        output.latched();
+        output.latched(false);
         output.perform_screencopies(
             tex,
             None,

src/tasks.rs

@@ -1,5 +1,6 @@
 mod backend;
 mod connector;
+mod const_clock;
 mod drmdev;
 mod hardware_cursor;
 mod idle;
@@ -12,10 +13,11 @@ use {
         state::State,
         tasks::{
             backend::BackendEventHandler,
+            const_clock::run_const_clock,
             slow_clients::{SlowClientHandler, SlowEiClientHandler},
         },
     },
-    std::rc::Rc,
+    std::{rc::Rc, time::Duration},
 };
 pub use {hardware_cursor::handle_hardware_cursor_tick, idle::idle};
 
@@ -33,3 +35,12 @@ pub async fn handle_slow_ei_clients(state: Rc<State>) {
     let mut sch = SlowEiClientHandler { state };
     sch.handle_events().await;
 }
+
+pub async fn handle_const_40hz_latch(state: Rc<State>) {
+    let output = state.dummy_output.get().unwrap();
+    let duration = Duration::from_nanos(1_000_000_000 / 40);
+    run_const_clock(duration, &state.ring, &state.const_40hz_latch, |l| {
+        l.after_latch(&output, false)
+    })
+    .await;
+}

src/tasks/const_clock.rs

@@ -0,0 +1,49 @@
+use {
+    crate::{
+        io_uring::IoUring,
+        utils::{
+            asyncevent::AsyncEvent, errorfmt::ErrorFmt, event_listener::EventSource, timer::TimerFd,
+        },
+    },
+    std::{rc::Rc, time::Duration},
+    uapi::c,
+};
+
+pub async fn run_const_clock<T, F>(
+    duration: Duration,
+    ring: &Rc<IoUring>,
+    source: &EventSource<T>,
+    mut f: F,
+) where
+    T: ?Sized,
+    F: FnMut(Rc<T>),
+{
+    let timer = match TimerFd::new(c::CLOCK_MONOTONIC) {
+        Ok(fd) => fd,
+        Err(e) => {
+            log::error!("Could not create timerfd: {}", ErrorFmt(e));
+            return;
+        }
+    };
+    if let Err(e) = timer.program(Some(duration), Some(duration)) {
+        log::error!("Could not program timerfd: {}", ErrorFmt(e));
+        return;
+    }
+    let ae = Rc::new(AsyncEvent::default());
+    loop {
+        if let Err(e) = timer.expired(&ring).await {
+            log::error!("Could not wait for timerfd to expire: {}", ErrorFmt(e));
+            return;
+        }
+        let mut dispatched_any = false;
+        for el in source.iter() {
+            dispatched_any = true;
+            f(el);
+        }
+        if !dispatched_any {
+            let ae2 = ae.clone();
+            source.on_attach(Box::new(move || ae2.trigger()));
+            ae.triggered().await;
+        }
+    }
+}

src/tree/output.rs

@@ -95,7 +95,7 @@ pub struct OutputNode {
 }
 
 pub trait LatchListener {
-    fn after_latch(self: Rc<Self>, on: &OutputNode);
+    fn after_latch(self: Rc<Self>, on: &OutputNode, tearing: bool);
 }
 
 pub trait VblankListener {
@@ -135,10 +135,10 @@ pub async fn output_render_data(state: Rc<State>) {
 }
 
 impl OutputNode {
-    pub fn latched(&self) {
+    pub fn latched(&self, tearing: bool) {
         self.schedule.latched();
         for listener in self.latch_event.iter() {
-            listener.after_latch(self);
+            listener.after_latch(self, tearing);
         }
     }
 

wire/wp_fifo_manager_v1.txt

@@ -0,0 +1,8 @@
+request destroy {
+
+}
+
+request get_fifo {
+    id: id(wp_fifo_v1),
+    surface: id(wl_surface),
+}

wire/wp_fifo_v1.txt

@@ -0,0 +1,11 @@
+request set_barrier {
+
+}
+
+request wait_barrier {
+
+}
+
+request destroy {
+
+}