perf: share ScreenCaptureKit warm-up and prewarm early

richiemcilroy · richiemcilroy · commit c3d130e95c70 · 2025-09-27T13:49:20.000+01:00
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/apps/desktop/src-tauri/src/lib.rs b/apps/desktop/src-tauri/src/lib.rs
@@ -79,6 +79,8 @@ use tauri_plugin_notification::{NotificationExt, PermissionState};
 use tauri_plugin_opener::OpenerExt;
 use tauri_plugin_shell::ShellExt;
 use tauri_specta::Event;
+#[cfg(target_os = "macos")]
+use tokio::sync::Mutex;
 use tokio::sync::{RwLock, oneshot};
 use tracing::{error, trace};
 use upload::{S3UploadMeta, create_or_get_video, upload_image, upload_video};
@@ -320,13 +322,94 @@ pub struct RequestOpenSettings {
     page: String,
 }
 
+#[derive(Deserialize, specta::Type, Serialize, tauri_specta::Event, Debug, Clone)]
+pub struct RequestScreenCapturePrewarm {
+    #[serde(default)]
+    pub force: bool,
+}
+
 #[derive(Deserialize, specta::Type, Serialize, tauri_specta::Event, Debug, Clone)]
 pub struct NewNotification {
     title: String,
     body: String,
     is_error: bool,
 }
 
+#[cfg(target_os = "macos")]
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum PrewarmState {
+    Idle,
+    Warming,
+    Warmed,
+}
+
+#[cfg(target_os = "macos")]
+pub(crate) struct ScreenCapturePrewarmer {
+    state: Mutex<PrewarmState>,
+}
+
+#[cfg(target_os = "macos")]
+impl Default for ScreenCapturePrewarmer {
+    fn default() -> Self {
+        Self {
+            state: Mutex::new(PrewarmState::Idle),
+        }
+    }
+}
+
+#[cfg(target_os = "macos")]
+impl ScreenCapturePrewarmer {
+    async fn request(&self, force: bool) {
+        let should_start = {
+            let mut state = self.state.lock().await;
+
+            if force {
+                *state = PrewarmState::Idle;
+            }
+
+            match *state {
+                PrewarmState::Idle => {
+                    *state = PrewarmState::Warming;
+                    true
+                }
+                PrewarmState::Warming => {
+                    trace!("ScreenCaptureKit prewarm already in progress");
+                    false
+                }
+                PrewarmState::Warmed => {
+                    if force {
+                        *state = PrewarmState::Warming;
+                        true
+                    } else {
+                        trace!("ScreenCaptureKit cache already warmed");
+                        false
+                    }
+                }
+            }
+        };
+
+        if !should_start {
+            return;
+        }
+
+        let warm_start = std::time::Instant::now();
+        let result = scap_targets::prewarm_shareable_content().await;
+
+        let mut state = self.state.lock().await;
+        match result {
+            Ok(()) => {
+                let elapsed_ms = warm_start.elapsed().as_micros() as f64 / 1000.0;
+                *state = PrewarmState::Warmed;
+                trace!(elapsed_ms, "ScreenCaptureKit cache warmed");
+            }
+            Err(error) => {
+                *state = PrewarmState::Idle;
+                tracing::warn!(error = %error, "ScreenCaptureKit prewarm failed");
+            }
+        }
+    }
+}
+
 type ArcLock<T> = Arc<RwLock<T>>;
 pub type MutableState<'a, T> = State<'a, Arc<RwLock<T>>>;
 
@@ -1937,6 +2020,7 @@ pub async fn run(recording_logging_handle: LoggingHandle) {
             RequestOpenRecordingPicker,
             RequestNewScreenshot,
             RequestOpenSettings,
+            RequestScreenCapturePrewarm,
             NewNotification,
             AuthenticationInvalid,
             audio_meter::AudioInputLevelChange,
@@ -2075,6 +2159,8 @@ pub async fn run(recording_logging_handle: LoggingHandle) {
             fake_window::init(&app);
             app.manage(target_select_overlay::WindowFocusManager::default());
             app.manage(EditorWindowIds::default());
+            #[cfg(target_os = "macos")]
+            app.manage(ScreenCapturePrewarmer::default());
 
             tokio::spawn({
                 let camera_feed = camera_feed.clone();
@@ -2204,6 +2290,12 @@ pub async fn run(recording_logging_handle: LoggingHandle) {
                 .await;
             });
 
+            #[cfg(target_os = "macos")]
+            RequestScreenCapturePrewarm::listen_any_spawn(&app, async |event, app| {
+                let prewarmer = app.state::<ScreenCapturePrewarmer>();
+                prewarmer.request(event.force).await;
+            });
+
             let app_handle = app.clone();
             app.deep_link().on_open_url(move |event| {
                 deeplink_actions::handle(&app_handle, event.urls());
diff --git a/apps/desktop/src-tauri/src/windows.rs b/apps/desktop/src-tauri/src/windows.rs
@@ -16,11 +16,12 @@ use tauri::{
     AppHandle, LogicalPosition, Manager, Monitor, PhysicalPosition, PhysicalSize, WebviewUrl,
     WebviewWindow, WebviewWindowBuilder, Wry,
 };
+use tauri_specta::Event;
 use tokio::sync::RwLock;
-use tracing::{debug, error};
+use tracing::{debug, error, warn};
 
 use crate::{
-    App, ArcLock, fake_window,
+    App, ArcLock, RequestScreenCapturePrewarm, ScreenCapturePrewarmer, fake_window,
     general_settings::{AppTheme, GeneralSettingsStore},
     permissions,
     recording_settings::RecordingTargetMode,
@@ -274,6 +275,19 @@ impl ShowCapWindow {
                     crate::platform::set_window_level(window.as_ref().window(), 50);
                 }
 
+                #[cfg(target_os = "macos")]
+                {
+                    let app_handle = app.clone();
+                    tauri::async_runtime::spawn(async move {
+                        let prewarmer = app_handle.state::<ScreenCapturePrewarmer>();
+                        prewarmer.request(false).await;
+                    });
+
+                    if let Err(error) = (RequestScreenCapturePrewarm { force: false }).emit(app) {
+                        warn!(%error, "Failed to emit ScreenCaptureKit prewarm event");
+                    }
+                }
+
                 window
             }
             Self::TargetSelectOverlay { display_id } => {
diff --git a/apps/desktop/src/utils/tauri.ts b/apps/desktop/src/utils/tauri.ts
@@ -290,6 +290,7 @@ renderFrameEvent: RenderFrameEvent,
 requestNewScreenshot: RequestNewScreenshot,
 requestOpenRecordingPicker: RequestOpenRecordingPicker,
 requestOpenSettings: RequestOpenSettings,
+requestScreenCapturePrewarm: RequestScreenCapturePrewarm,
 requestStartRecording: RequestStartRecording,
 targetUnderCursor: TargetUnderCursor
 }>({
@@ -311,6 +312,7 @@ renderFrameEvent: "render-frame-event",
 requestNewScreenshot: "request-new-screenshot",
 requestOpenRecordingPicker: "request-open-recording-picker",
 requestOpenSettings: "request-open-settings",
+requestScreenCapturePrewarm: "request-screen-capture-prewarm",
 requestStartRecording: "request-start-recording",
 targetUnderCursor: "target-under-cursor"
 })
@@ -432,6 +434,7 @@ export type RenderFrameEvent = { frame_number: number; fps: number; resolution_b
 export type RequestNewScreenshot = null
 export type RequestOpenRecordingPicker = { target_mode: RecordingTargetMode | null }
 export type RequestOpenSettings = { page: string }
+export type RequestScreenCapturePrewarm = { force?: boolean }
 export type RequestStartRecording = { mode: RecordingMode }
 export type S3UploadMeta = { id: string }
 export type SceneMode = "default" | "cameraOnly" | "hideCamera"
diff --git a/crates/recording/src/capture_pipeline.rs b/crates/recording/src/capture_pipeline.rs
@@ -787,6 +787,21 @@ pub async fn create_screen_capture(
 ) -> Result<ScreenCaptureReturn<ScreenCaptureMethod>, RecordingError> {
     let (video_tx, video_rx) = flume::bounded(16);
 
+    #[cfg(target_os = "macos")]
+    {
+        let warm_start = std::time::Instant::now();
+        match scap_targets::prewarm_shareable_content().await {
+            Ok(()) => tracing::trace!(
+                elapsed_ms = warm_start.elapsed().as_micros() as f64 / 1000.0,
+                "ScreenCaptureKit cache ensured before capture"
+            ),
+            Err(error) => tracing::warn!(
+                error = %error,
+                "ScreenCaptureKit prewarm failed before capture"
+            ),
+        }
+    }
+
     ScreenCaptureSource::<ScreenCaptureMethod>::init(
         capture_target,
         force_show_cursor,
diff --git a/crates/recording/src/pipeline/builder.rs b/crates/recording/src/pipeline/builder.rs
@@ -122,7 +122,7 @@ impl PipelineBuilder {
         // TODO: Shut down tasks if launch failed.
         for (name, task) in tasks.into_iter() {
             // TODO: Wait for these in parallel?
-            tokio::time::timeout(Duration::from_secs(5), task.ready_signal.recv_async())
+            tokio::time::timeout(Duration::from_secs(15), task.ready_signal.recv_async())
                 .await
                 .map_err(|_| MediaError::TaskLaunch(format!("task timed out: '{name}'")))?
                 .map_err(|e| MediaError::TaskLaunch(format!("'{name}' build / {e}")))??;
diff --git a/crates/scap-targets/Cargo.toml b/crates/scap-targets/Cargo.toml
@@ -18,6 +18,7 @@ core-graphics = "0.24.0"
 core-foundation = "0.10.0"
 cocoa = "0.26.0"
 objc = "0.2.7"
+tokio = { workspace = true, features = ["sync"] }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 windows = { workspace = true, features = [
diff --git a/crates/scap-targets/src/lib.rs b/crates/scap-targets/src/lib.rs
@@ -2,6 +2,8 @@ pub mod bounds;
 pub mod platform;
 
 use bounds::*;
+#[cfg(target_os = "macos")]
+pub use platform::prewarm_shareable_content;
 pub use platform::{DisplayIdImpl, DisplayImpl, WindowIdImpl, WindowImpl};
 use serde::{Deserialize, Serialize};
 use specta::Type;
diff --git a/crates/scap-targets/src/platform/macos.rs b/crates/scap-targets/src/platform/macos.rs
@@ -15,6 +15,13 @@ use core_graphics::{
 };
 
 use crate::bounds::{LogicalBounds, LogicalPosition, LogicalSize, PhysicalSize};
+use tracing::{trace, warn};
+
+mod cache;
+
+pub async fn prewarm_shareable_content() -> Result<(), arc::R<ns::Error>> {
+    cache::prewarm_shareable_content().await
+}
 
 #[derive(Clone, Copy)]
 pub struct DisplayImpl(CGDisplay);
@@ -174,13 +181,17 @@ impl DisplayImpl {
 
 impl DisplayImpl {
     pub async fn as_sc(&self) -> Option<arc::R<sc::Display>> {
-        sc::ShareableContent::current()
-            .await
-            .ok()?
-            .displays()
-            .iter()
-            .find(|d| d.display_id().0 == self.0.id)
-            .map(|v| v.retained())
+        match cache::get_display(self.0.id).await {
+            Ok(display) => display,
+            Err(error) => {
+                warn!(
+                    display_id = self.0.id,
+                    error = %error,
+                    "Failed to access ScreenCaptureKit display cache"
+                );
+                None
+            }
+        }
     }
 
     pub async fn as_content_filter(&self) -> Option<arc::R<sc::ContentFilter>> {
@@ -191,13 +202,40 @@ impl DisplayImpl {
         &self,
         windows: Vec<arc::R<sc::Window>>,
     ) -> Option<arc::R<sc::ContentFilter>> {
-        let excluded_windows =
-            ns::Array::from_slice_retained(windows.into_iter().collect::<Vec<_>>().as_slice());
+        let lookup_start = std::time::Instant::now();
+
+        let display = match cache::get_display(self.0.id).await {
+            Ok(Some(display)) => display,
+            Ok(None) => {
+                warn!(
+                    display_id = self.0.id,
+                    "Display missing from ScreenCaptureKit cache"
+                );
+                return None;
+            }
+            Err(error) => {
+                warn!(
+                    display_id = self.0.id,
+                    error = %error,
+                    "Failed to resolve ScreenCaptureKit display"
+                );
+                return None;
+            }
+        };
+
+        let windows = windows.into_iter().collect::<Vec<_>>();
+        let excluded_windows = ns::Array::from_slice_retained(windows.as_slice());
 
-        Some(sc::ContentFilter::with_display_excluding_windows(
-            self.as_sc().await?.as_ref(),
-            &excluded_windows,
-        ))
+        let filter =
+            sc::ContentFilter::with_display_excluding_windows(display.as_ref(), &excluded_windows);
+
+        trace!(
+            display_id = self.0.id,
+            elapsed_ms = lookup_start.elapsed().as_micros() as f64 / 1000.0,
+            "Created ScreenCaptureKit content filter"
+        );
+
+        Some(filter)
     }
 }
 
@@ -449,13 +487,17 @@ impl WindowImpl {
     }
 
     pub async fn as_sc(&self) -> Option<arc::R<sc::Window>> {
-        sc::ShareableContent::current()
-            .await
-            .ok()?
-            .windows()
-            .iter()
-            .find(|w| w.id() == self.0)
-            .map(|v| v.retained())
+        match cache::get_window(self.0).await {
+            Ok(window) => window,
+            Err(error) => {
+                warn!(
+                    window_id = self.0,
+                    error = %error,
+                    "Failed to access ScreenCaptureKit window cache"
+                );
+                None
+            }
+        }
     }
 
     pub fn display(&self) -> Option<DisplayImpl> {
diff --git a/crates/scap-targets/src/platform/macos/cache.rs b/crates/scap-targets/src/platform/macos/cache.rs
