config: allow disabling direct scanout

jay-config/src/_private/client.rs

@@ -511,6 +511,10 @@ impl Client {
         self.send(&ClientMessage::SetGfxApi { device, api });
     }
 
+    pub fn set_direct_scanout_enabled(&self, device: Option<DrmDevice>, enabled: bool) {
+        self.send(&ClientMessage::SetDirectScanoutEnabled { device, enabled });
+    }
+
     pub fn connector_connected(&self, connector: Connector) -> bool {
         let res = self.send_with_response(&ClientMessage::ConnectorConnected { connector });
         get_response!(res, false, ConnectorConnected { connected });

jay-config/src/_private/ipc.rs

@@ -338,6 +338,10 @@ pub enum ClientMessage<'a> {
         device: Option<DrmDevice>,
         api: GfxApi,
     },
+    SetDirectScanoutEnabled {
+        device: Option<DrmDevice>,
+        enabled: bool,
+    },
 }
 
 #[derive(Serialize, Deserialize, Debug)]

jay-config/src/video.rs

@@ -369,6 +369,11 @@ impl DrmDevice {
     pub fn set_gfx_api(self, gfx_api: GfxApi) {
         get!().set_gfx_api(Some(self), gfx_api);
     }
+
+    /// Enables or disables direct scanout of client surfaces for this device.
+    pub fn set_direct_scanout_enabled(self, enabled: bool) {
+        get!().set_direct_scanout_enabled(Some(self), enabled);
+    }
 }
 
 /// A graphics API.
@@ -389,3 +394,12 @@ pub enum GfxApi {
 pub fn set_gfx_api(gfx_api: GfxApi) {
     get!().set_gfx_api(None, gfx_api);
 }
+
+/// Enables or disables direct scanout of client surfaces.
+///
+/// The default is `true`.
+///
+/// This setting can be overwritten per-device with [DrmDevice::set_direct_scanout_enabled].
+pub fn set_direct_scanout_enabled(enabled: bool) {
+    get!().set_direct_scanout_enabled(None, enabled);
+}

src/backend.rs

@@ -230,4 +230,5 @@ pub trait BackendDrmDevice {
     fn set_gfx_api(&self, api: GfxApi);
     fn gtx_api(&self) -> GfxApi;
     fn version(&self) -> Result<DrmVersion, DrmError>;
+    fn set_direct_scanout_enabled(&self, enabled: bool);
 }

src/backends/metal/video.rs

@@ -81,6 +81,7 @@ pub struct MetalDrmDevice {
     pub handle_events: HandleEvents,
     pub ctx: CloneCell<Rc<MetalRenderContext>>,
     pub on_change: OnChange<crate::backend::DrmEvent>,
+    pub direct_scanout_enabled: Cell<Option<bool>>,
 }
 
 impl BackendDrmDevice for MetalDrmDevice {
@@ -115,6 +116,10 @@ impl BackendDrmDevice for MetalDrmDevice {
     fn version(&self) -> Result<DrmVersion, DrmError> {
         self.gbm.drm.version()
     }
+
+    fn set_direct_scanout_enabled(&self, enabled: bool) {
+        self.direct_scanout_enabled.set(Some(enabled));
+    }
 }
 
 pub struct HandleEvents {
@@ -466,6 +471,13 @@ impl MetalConnector {
         data
     }
 
+    fn direct_scanout_enabled(&self) -> bool {
+        self.dev
+            .direct_scanout_enabled
+            .get()
+            .unwrap_or(self.state.direct_scanout_enabled.get())
+    }
+
     fn prepare_present_fb(
         &self,
         rr: &mut RenderResult,
@@ -485,7 +497,9 @@ impl MetalConnector {
             output.global.preferred_scale.get(),
             render_hw_cursor,
         );
-        let try_direct_scanout = try_direct_scanout && !output.global.have_shm_screencopies();
+        let try_direct_scanout = try_direct_scanout
+            && !output.global.have_shm_screencopies()
+            && self.direct_scanout_enabled();
         let mut direct_scanout_data = None;
         if try_direct_scanout {
             if let Some(dsd) = self.prepare_direct_scanout(&pass, plane) {
@@ -1394,6 +1408,7 @@ impl MetalBackend {
             },
             ctx: CloneCell::new(ctx),
             on_change: Default::default(),
+            direct_scanout_enabled: Default::default(),
         });
 
         let (connectors, futures) = get_connectors(self, &dev, &resources.connectors)?;

src/backends/x.rs

@@ -989,6 +989,10 @@ impl BackendDrmDevice for XDrmDevice {
     fn version(&self) -> Result<DrmVersion, DrmError> {
         self.backend.gbm.drm.version()
     }
+
+    fn set_direct_scanout_enabled(&self, enabled: bool) {
+        let _ = enabled;
+    }
 }
 
 struct XOutput {

src/compositor.rs

@@ -203,6 +203,7 @@ fn start_compositor2(
         toplevel_lists: Default::default(),
         dma_buf_ids: Default::default(),
         drm_feedback_ids: Default::default(),
+        direct_scanout_enabled: Cell::new(true),
     });
     state.tracker.register(ClientId::from_raw(0));
     create_dummy_output(&state);

src/config/handler.rs

@@ -590,6 +590,21 @@ impl ConfigProxyHandler {
         Ok(())
     }
 
+    fn handle_set_direct_scanout_enabled(
+        &self,
+        device: Option<DrmDevice>,
+        enabled: bool,
+    ) -> Result<(), CphError> {
+        match device {
+            Some(dev) => self
+                .get_drm_device(dev)?
+                .dev
+                .set_direct_scanout_enabled(enabled),
+            _ => self.state.direct_scanout_enabled.set(enabled),
+        }
+        Ok(())
+    }
+
     fn handle_get_default_workspace_capture(&self) {
         self.respond(Response::GetDefaultWorkspaceCapture {
             capture: self.state.default_workspace_capture.get(),
@@ -1320,6 +1335,9 @@ impl ConfigProxyHandler {
             ClientMessage::SetGfxApi { device, api } => {
                 self.handle_set_gfx_api(device, api).wrn("set_gfx_api")?
             }
+            ClientMessage::SetDirectScanoutEnabled { device, enabled } => self
+                .handle_set_direct_scanout_enabled(device, enabled)
+                .wrn("set_direct_scanout_enabled")?,
         }
         Ok(())
     }

src/state.rs

@@ -144,6 +144,7 @@ pub struct State {
         CopyHashMap<(ClientId, ExtForeignToplevelListV1Id), Rc<ExtForeignToplevelListV1>>,
     pub dma_buf_ids: DmaBufIds,
     pub drm_feedback_ids: DrmFeedbackIds,
+    pub direct_scanout_enabled: Cell<bool>,
 }
 
 // impl Drop for State {