Redraw on demand rather than continuously

src/handlers/compositor.rs

@@ -41,6 +41,8 @@ impl CompositorHandler for Niri {
 
         xdg_shell::handle_commit(&self.space, surface);
         resize_grab::handle_commit(&mut self.space, surface);
+
+        self.queue_redraw();
     }
 }
 

src/input.rs

@@ -89,6 +89,9 @@ impl Niri {
                         utime: event.time(),
                     },
                 );
+
+                // Redraw to update the cursor position.
+                self.queue_redraw();
             }
             InputEvent::PointerMotionAbsolute { event, .. } => {
                 let output = self.space.outputs().next().unwrap();
@@ -112,6 +115,9 @@ impl Niri {
                         time: event.time_msec(),
                     },
                 );
+
+                // Redraw to update the cursor position.
+                self.queue_redraw();
             }
             InputEvent::PointerButton { event, .. } => {
                 let pointer = self.seat.get_pointer().unwrap();

src/niri.rs

@@ -12,6 +12,7 @@ use smithay::input::keyboard::XkbConfig;
 use smithay::input::{Seat, SeatState};
 use smithay::output::Output;
 use smithay::reexports::calloop::generic::Generic;
+use smithay::reexports::calloop::timer::{TimeoutAction, Timer};
 use smithay::reexports::calloop::{Interest, LoopHandle, LoopSignal, Mode, PostAction};
 use smithay::reexports::wayland_server::backend::{ClientData, ClientId, DisconnectReason};
 use smithay::reexports::wayland_server::protocol::wl_surface::WlSurface;
@@ -45,6 +46,11 @@ pub struct Niri {
 
     pub seat: Seat<Self>,
     pub output: Option<Output>,
+
+    // Set to `true` if there's a redraw queued on the event loop. Reset to `false` in redraw()
+    // which means that you cannot queue more than one redraw at once.
+    pub redraw_queued: bool,
+    pub waiting_for_vblank: bool,
 }
 
 impl Niri {
@@ -119,6 +125,8 @@ impl Niri {
 
             seat,
             output: None,
+            redraw_queued: false,
+            waiting_for_vblank: false,
         }
     }
 
@@ -135,7 +143,32 @@ impl Niri {
             })
     }
 
-    pub fn redraw(&mut self, backend: &mut dyn Backend) {
+    /// Schedules an immediate redraw if one is not already scheduled.
+    pub fn queue_redraw(&mut self) {
+        if self.redraw_queued || self.waiting_for_vblank {
+            return;
+        }
+
+        self.redraw_queued = true;
+
+        self.event_loop
+            .insert_source(Timer::immediate(), |_, _, data| {
+                let backend: &mut dyn Backend = if let Some(tty) = &mut data.tty {
+                    tty
+                } else {
+                    data.winit.as_mut().unwrap()
+                };
+                data.niri.redraw(backend);
+                TimeoutAction::Drop
+            })
+            .unwrap();
+    }
+
+    fn redraw(&mut self, backend: &mut dyn Backend) {
+        assert!(self.redraw_queued);
+        assert!(!self.waiting_for_vblank);
+        self.redraw_queued = false;
+
         let elements = space_render_elements(
             backend.renderer(),
             [&self.space],

src/tty.rs

@@ -1,6 +1,5 @@
 use std::os::fd::FromRawFd;
 use std::path::PathBuf;
-use std::time::Duration;
 
 use anyhow::anyhow;
 use smithay::backend::allocator::dmabuf::Dmabuf;
@@ -17,7 +16,6 @@ use smithay::backend::session::libseat::LibSeatSession;
 use smithay::backend::session::{Event as SessionEvent, Session};
 use smithay::backend::udev::{self, UdevBackend, UdevEvent};
 use smithay::output::{Mode, Output, OutputModeSource, PhysicalProperties, Subpixel};
-use smithay::reexports::calloop::timer::{TimeoutAction, Timer};
 use smithay::reexports::calloop::{LoopHandle, RegistrationToken};
 use smithay::reexports::drm::control::connector::{
     Interface as ConnectorInterface, State as ConnectorState,
@@ -83,7 +81,7 @@ impl Backend for Tty {
                 assert!(!res.needs_sync());
                 if res.damage.is_some() {
                     match output_device.drm_compositor.queue_frame(()) {
-                        Ok(()) => return,
+                        Ok(()) => niri.waiting_for_vblank = true,
                         Err(err) => {
                             error!("error queueing frame: {err}");
                         }
@@ -95,17 +93,6 @@ impl Backend for Tty {
                 error!("error rendering frame: {err}");
             }
         }
-
-        // FIXME: render on demand instead of busy looping.
-        niri.event_loop
-            .insert_source(
-                Timer::from_duration(Duration::from_millis(6)),
-                |_, _, data| {
-                    data.niri.redraw(data.tty.as_mut().unwrap());
-                    TimeoutAction::Drop
-                },
-            )
-            .unwrap();
     }
 }
 
@@ -157,7 +144,7 @@ impl Tty {
                             output_device.drm_compositor.reset_buffers();
                         }
 
-                        niri.redraw(tty);
+                        niri.queue_redraw();
                     }
                 }
             })
@@ -190,7 +177,7 @@ impl Tty {
                         if let Err(err) = tty.device_added(device_id, path, niri) {
                             warn!("error adding device: {err:?}");
                         }
-                        niri.redraw(tty);
+                        niri.queue_redraw();
                     }
                     UdevEvent::Changed { device_id } => tty.device_changed(device_id, niri),
                     UdevEvent::Removed { device_id } => tty.device_removed(device_id, niri),
@@ -198,7 +185,7 @@ impl Tty {
             })
             .unwrap();
 
-        niri.redraw(self);
+        niri.queue_redraw();
     }
 
     fn device_added(
@@ -250,11 +237,8 @@ impl Tty {
                         //     .windows
                         //     .mark_presented(&output_device.last_render_states, metadata);
 
-                        // Request redraw before the next VBlank.
-                        // let frame_interval = catacomb.windows.output().frame_interval();
-                        // let duration = frame_interval - RENDER_TIME_OFFSET;
-                        // catacomb.backend.schedule_redraw(duration);
-                        data.niri.redraw(tty);
+                        data.niri.waiting_for_vblank = false;
+                        data.niri.queue_redraw();
                     }
                     DrmEvent::Error(error) => error!("DRM error: {error}"),
                 };

src/winit.rs

@@ -115,16 +115,17 @@ impl Winit {
                     );
                 }
                 WinitEvent::Input(event) => niri.process_input_event(&mut |_| (), event),
-                _ => (),
+                WinitEvent::Focus(_) => (),
+                WinitEvent::Refresh => niri.queue_redraw(),
             });
 
-        if let Err(WinitError::WindowClosed) = res {
+        // I want this to stop compiling if more errors are added.
+        #[allow(clippy::single_match)]
+        match res {
+            Err(WinitError::WindowClosed) => {
                 niri.stop_signal.stop();
-            return;
-        } else {
-            res.unwrap();
             }
-
-        niri.redraw(self);
+            Ok(()) => (),
+        }
     }
 }