Optimize scroll export and gate short scroll selections

native/macos-host/Sources/RsnapNativeHostKit/CaptureHostView.swift

@@ -881,6 +881,9 @@ final class CaptureHostView: NSView {
 					controller?.recognizeText()
 					return
 				case "s":
+					guard toolbarItem(.scroll)?.enabled == true else {
+						return
+					}
 					controller?.startScrollCapture(source: "keyboard_s")
 					return
 				default:

native/macos-host/Sources/RsnapNativeHostKit/CaptureSessionController+Export.swift

@@ -7,7 +7,7 @@ import RsnapHostBridge
 private struct FrozenSelectionImageRenderRequest: @unchecked Sendable {
 	let captureID: UInt64
 	let selection: CGRect
-	let scrollExportImage: CGImage?
+	let scrollExportSnapshot: RGBARegionSnapshot?
 	let frozenDisplayFrame: CGRect?
 	let frozenDisplayImage: CGImage?
 	let frozenBaseImage: CGImage?
@@ -25,8 +25,8 @@ private struct FrozenSelectionImageRenderRequest: @unchecked Sendable {
 		FrozenPreparedExportKey(
 			captureID: captureID,
 			selection: selection,
-			scrollExportWidth: scrollExportImage?.width ?? 0,
-			scrollExportHeight: scrollExportImage?.height ?? 0,
+			scrollExportWidth: scrollExportSnapshot?.width ?? 0,
+			scrollExportHeight: scrollExportSnapshot?.height ?? 0,
 			frozenDisplayFrame: frozenDisplayFrame,
 			frozenBaseWidth: frozenBaseImage?.width ?? 0,
 			frozenBaseHeight: frozenBaseImage?.height ?? 0,
@@ -45,7 +45,7 @@ private struct FrozenSelectionImageRenderRequest: @unchecked Sendable {
 	var canPrepareExportInBackground: Bool {
 		// Scroll capture exports change as the stitched document grows; prepare those on demand
 		// until the scroll pipeline exposes a stable export revision.
-		scrollExportImage == nil
+		scrollExportSnapshot == nil
 	}
 }
 
@@ -273,8 +273,8 @@ extension CaptureSessionController {
 		guard let selection = currentFrozenSelection() else {
 			return nil
 		}
-		let scrollExportImage =
-			scrollCaptureState == nil ? nil : try activeScrollCaptureExportImage()
+		let scrollExportSnapshot =
+			scrollCaptureState == nil ? nil : try activeScrollCaptureExportSnapshot()
 		let settings = settingsStore.settings
 		let selectionCenter = CGPoint(x: selection.midX, y: selection.midY)
 		let screen = screen(containing: selectionCenter)
@@ -285,7 +285,7 @@ extension CaptureSessionController {
 		return FrozenSelectionImageRenderRequest(
 			captureID: currentCaptureTelemetryID,
 			selection: selection,
-			scrollExportImage: scrollExportImage,
+			scrollExportSnapshot: scrollExportSnapshot,
 			frozenDisplayFrame: chromeState.frozenDisplayFrame,
 			frozenDisplayImage: chromeState.frozenDisplayImage,
 			frozenBaseImage: chromeState.frozenBaseImage,
@@ -603,20 +603,14 @@ extension CaptureSessionController {
 		)
 	}
 
-	func activeScrollCaptureExportImage() throws -> CGImage? {
+	func activeScrollCaptureExportSnapshot() throws -> RGBARegionSnapshot? {
 		guard Self.scrollCaptureEnabled else {
 			return nil
 		}
 		guard let state = scrollCaptureState else {
 			return nil
 		}
-		guard
-			let export = try state.stitcher.exportImage(),
-			let exportImage = NativeHostImageBridge.cgImage(from: export)
-		else {
-			return nil
-		}
-		return exportImage
+		return try state.stitcher.exportImage()
 	}
 
 	func captureFrozenSelectionImage(applyingCaptureFrameEffect: Bool = false) throws
@@ -658,7 +652,7 @@ extension CaptureSessionController {
 		prefersPixelSnapshot: Bool = false
 	) throws -> FrozenSelectionImageRenderResult {
 		let captureStartedAt = ProcessInfo.processInfo.systemUptime
-		if let scrollExport = request.scrollExportImage {
+		if let scrollExport = request.scrollExportSnapshot {
 			return renderScrollExportImage(
 				scrollExport,
 				request: request,
@@ -676,21 +670,22 @@ extension CaptureSessionController {
 	}
 
 	nonisolated private static func renderScrollExportImage(
-		_ scrollExport: CGImage,
+		_ scrollExport: RGBARegionSnapshot,
 		request: FrozenSelectionImageRenderRequest,
 		captureStartedAt: TimeInterval,
 		applyingCaptureFrameEffect: Bool,
 		prefersPixelSnapshot: Bool
 	) -> FrozenSelectionImageRenderResult {
+		let base = FrozenRenderedImage(image: nil, rgbaSnapshot: scrollExport)
 		let result =
 			applyingCaptureFrameEffect
 			? applyCaptureFrameEffectIfNeeded(
-				to: scrollExport,
+				to: base,
 				request: request,
 				hasOverlayEdits: false,
 				prefersPixelSnapshot: prefersPixelSnapshot
 			)
-			: FrozenRenderedImage(image: scrollExport, rgbaSnapshot: nil)
+			: resolvedRenderedImage(base, prefersPixelSnapshot: prefersPixelSnapshot)
 		logFrozenSelectionImageTiming(
 			request: request,
 			captureStartedAt: captureStartedAt,

native/macos-host/Sources/RsnapNativeHostKit/CaptureSessionController+FrozenInteraction.swift

@@ -92,6 +92,11 @@ extension CaptureSessionController {
 		if chromeState.frozenSelectionEditable == false {
 			return "not_dragged_region"
 		}
+		if let selection = currentFrozenSelection(),
+			scrollCaptureSelectionHasSufficientHeight(selection) == false
+		{
+			return "selection_too_short"
+		}
 		return "unavailable"
 	}
 
@@ -105,18 +110,24 @@ extension CaptureSessionController {
 			return "Scroll Capture requires a dragged region selection."
 		case "no_selection", "requires_frozen":
 			return "Select a dragged region before starting Scroll Capture."
+		case "selection_too_short":
+			return "Select a taller region before starting Scroll Capture."
 		default:
 			return "Scroll Capture is not available for this selection."
 		}
 	}
 
 	private func scrollCaptureEntryDetail(source: String, reason: String) -> String {
-		[
+		let selection = currentFrozenSelection()
+
+		return [
 			"source=\(source)",
 			"reason=\(reason)",
 			"scene=\(scene.mode)",
 			"editable=\(chromeState.frozenSelectionEditable)",
-			"has_selection=\(currentFrozenSelection() != nil)",
+			"has_selection=\(selection != nil)",
+			"selection_height_px=\(selection.map { scrollCaptureSelectionHeightPixels($0) } ?? 0)",
+			"minimum_height_px=\(Self.scrollCaptureMinimumSelectionHeightPixels)",
 			"active=\(scrollCaptureState != nil)",
 		].joined(separator: " ")
 	}

native/macos-host/Sources/RsnapNativeHostKit/CaptureSessionController+ScrollCapture.swift

@@ -48,11 +48,15 @@ extension CaptureSessionController {
 	private static let scrollCaptureQueuedWheelDeltaLimitMultiplier = 32.0
 
 	var scrollCaptureToolbarEnabled: Bool {
-		Self.scrollCaptureEnabled
-			&& scene.mode == .frozen
-			&& scrollCaptureState == nil
-			&& chromeState.frozenSelectionEditable
-			&& currentFrozenSelection() != nil
+		guard Self.scrollCaptureEnabled,
+			scene.mode == .frozen,
+			scrollCaptureState == nil,
+			chromeState.frozenSelectionEditable,
+			let selection = currentFrozenSelection()
+		else {
+			return false
+		}
+		return scrollCaptureSelectionHasSufficientHeight(selection)
 	}
 
 	func handleScrollCaptureWheel(_ event: NSEvent, at point: CGPoint) -> Bool {
@@ -476,6 +480,11 @@ extension CaptureSessionController {
 			refreshOverlay()
 			return
 		}
+		guard scrollCaptureSelectionHasSufficientHeight(selection) else {
+			try setHostStatusMessage("Select a taller region before starting Scroll Capture.")
+			refreshOverlay()
+			return
+		}
 
 		guard
 			let captureSource = overlayController?.scrollCaptureFallbackSource(
@@ -1098,6 +1107,24 @@ extension CaptureSessionController {
 		return scrollCaptureFlippedDesktopPoint(fallbackAppKitPoint)
 	}
 
+	func scrollCaptureSelectionHasSufficientHeight(_ selection: CGRect) -> Bool {
+		scrollCaptureSelectionHeightPixels(selection)
+			>= Self.scrollCaptureMinimumSelectionHeightPixels
+	}
+
+	func scrollCaptureSelectionHeightPixels(_ selection: CGRect) -> Int {
+		if chromeState.frozenSelectionSnapshot == selection,
+			let frozenBaseImage = chromeState.frozenBaseImage
+		{
+			return frozenBaseImage.height
+		}
+		let point = CGPoint(x: selection.midX, y: selection.midY)
+		let scale =
+			screen(containing: point)?.backingScaleFactor
+			?? NSScreen.main?.backingScaleFactor
+			?? 1
+		return Int((selection.height * scale).rounded())
+	}
 }
 
 private func scrollCaptureFlippedDesktopPoint(_ point: CGPoint) -> CGPoint {

native/macos-host/Sources/RsnapNativeHostKit/CaptureSessionController.swift

@@ -31,6 +31,7 @@ final class CaptureSessionController: NSObject {
 	static let displayFirstFrameWait: TimeInterval = 0.025
 	static let coldSelfCaptureRecoveryWait: TimeInterval = 3.5
 	static let scrollCaptureEnabled = true
+	static let scrollCaptureMinimumSelectionHeightPixels = 120
 	static let scrollCaptureForwardingPassthrough: TimeInterval = 0.012
 	static let scrollCaptureControlledScrollSettleDelay: TimeInterval = 0.18
 	static let scrollCaptureInputLiveFrameMaxAge: TimeInterval = 0.18

packages/rsnap-host-ffi/src/lib.rs

@@ -1432,10 +1432,13 @@ pub unsafe extern "C" fn rsnap_scroll_session_observe_downward_frame(
 		Ok(outcome) => outcome,
 		Err(_err) => return RsnapStatus::InvalidInput,
 	};
-	let export = handle.session.export_image();
+	let (export_width, export_height) = handle.session.export_dimensions();
 
 	unsafe {
-		ptr::write(out_result, encode_scroll_observe_result(outcome, &export, &handle.session));
+		ptr::write(
+			out_result,
+			encode_scroll_observe_result(outcome, export_width, export_height, &handle.session),
+		);
 	}
 
 	RsnapStatus::Ok
@@ -1481,10 +1484,13 @@ pub unsafe extern "C" fn rsnap_scroll_session_observe_downward_frame_with_motion
 		Ok(outcome) => outcome,
 		Err(_err) => return RsnapStatus::InvalidInput,
 	};
-	let export = handle.session.export_image();
+	let (export_width, export_height) = handle.session.export_dimensions();
 
 	unsafe {
-		ptr::write(out_result, encode_scroll_observe_result(outcome, &export, &handle.session));
+		ptr::write(
+			out_result,
+			encode_scroll_observe_result(outcome, export_width, export_height, &handle.session),
+		);
 	}
 
 	RsnapStatus::Ok
@@ -1539,15 +1545,18 @@ pub unsafe extern "C" fn rsnap_scroll_session_undo_last_append(
 	}
 
 	let did_undo = handle.session.undo_last_append();
-	let export = handle.session.export_image();
+	let (export_width, export_height) = handle.session.export_dimensions();
 	let kind = if did_undo {
 		ScrollStitchObserveOutcome::PreviewUpdated
 	} else {
 		ScrollStitchObserveOutcome::NoChange
 	};
 
 	unsafe {
-		ptr::write(out_result, encode_scroll_observe_result(kind, &export, &handle.session));
+		ptr::write(
+			out_result,
+			encode_scroll_observe_result(kind, export_width, export_height, &handle.session),
+		);
 	}
 
 	RsnapStatus::Ok
@@ -3840,7 +3849,8 @@ fn encode_host_request(request: HostRequest) -> RsnapHostRequestValue {
 
 fn encode_scroll_observe_result(
 	outcome: ScrollStitchObserveOutcome,
-	export: &ScrollStitchImage,
+	export_width: u32,
+	export_height: u32,
 	session: &ScrollStitchSession,
 ) -> RsnapScrollObserveResult {
 	let (kind, growth_rows) = match outcome {
@@ -3859,8 +3869,8 @@ fn encode_scroll_observe_result(
 	RsnapScrollObserveResult {
 		kind: kind as u32,
 		growth_rows,
-		export_width: export.width,
-		export_height: export.height,
+		export_width,
+		export_height,
 		current_viewport_top_y: session.current_viewport_top_y(),
 	}
 }