WP-3b: ScreenCaptureKit capturer + region picker overlay per SPEC-A2a

2026-08-31 15:08:05 +04:00
parent 7379e4fbd7
commit 15021e9dda
3 changed files with 409 additions and 0 deletions
@@ -0,0 +1,118 @@
+import ScreenCaptureKit
+import CoreGraphics
+import ImageIO
+import UniformTypeIdentifiers
+import AppKit  // NSScreen only, to read backingScaleFactor as a fallback
+import Foundation
+
+public struct CapturedImage: Sendable {
+    public let pngData: Data
+    public let pixelWidth: Int
+    public let pixelHeight: Int
+    public let scale: CGFloat
+}
+
+public struct ScreenCapturer: Sendable {
+    public init() {}
+
+    /// Does NOT prompt. Reports the current Screen Recording grant.
+    public static var isScreenRecordingGranted: Bool { CGPreflightScreenCaptureAccess() }
+
+    /// Captures `region` at the display's true backing scale. Throws
+    /// `.screenRecordingNotGranted` when the grant is absent — never requests it.
+    public func capture(_ region: CaptureRegion) async throws -> CapturedImage {
+        guard Self.isScreenRecordingGranted else {
+            throw ShotdeckError.screenRecordingNotGranted
+        }
+
+        let content: SCShareableContent
+        do {
+            content = try await SCShareableContent.excludingDesktopWindows(
+                false,
+                onScreenWindowsOnly: true
+            )
+        } catch {
+            throw ShotdeckError.captureFailed(underlying: error.localizedDescription)
+        }
+
+        guard let display = content.displays.first(where: { $0.displayID == region.displayID }) else {
+            throw ShotdeckError.displayNoLongerConnected(displayID: region.displayID)
+        }
+
+        // Bounds/clamp: a resolution change often shrinks the display bounds by a few
+        // points without the region Ben picked being meaningfully wrong; 80% keeps a real
+        // recapture usable while a smaller overlap (e.g. a genuinely different display
+        // swapped in) still throws.
+        let rect: CGRect
+        if display.frame.contains(region.rect) {
+            rect = region.rect
+        } else {
+            let overlap = display.frame.intersection(region.rect)
+            let originalArea = region.rect.width * region.rect.height
+            let overlapArea = overlap.width * overlap.height
+            if originalArea > 0 && overlapArea / originalArea >= 0.8 {
+                rect = overlap
+            } else {
+                throw ShotdeckError.displayNoLongerConnected(displayID: region.displayID)
+            }
+        }
+
+        let localRect = CGRect(
+            x: rect.minX - display.frame.minX,
+            y: rect.minY - display.frame.minY,
+            width: rect.width,
+            height: rect.height
+        )
+
+        guard let mode = CGDisplayCopyDisplayMode(region.displayID) else {
+            throw ShotdeckError.captureFailed(
+                underlying: "no display mode for displayID \(region.displayID)"
+            )
+        }
+        guard mode.width > 0 else {
+            throw ShotdeckError.captureFailed(
+                underlying: "display mode width is 0 for displayID \(region.displayID)"
+            )
+        }
+        let scale = CGFloat(mode.pixelWidth) / CGFloat(mode.width)
+
+        let filter = SCContentFilter(display: display, excludingWindows: [])
+        let configuration = SCStreamConfiguration()
+        configuration.sourceRect = localRect
+        configuration.width = Int((localRect.width * scale).rounded())
+        configuration.height = Int((localRect.height * scale).rounded())
+        configuration.scalesToFit = false
+        configuration.showsCursor = false
+
+        let cgImage: CGImage
+        do {
+            cgImage = try await SCScreenshotManager.captureImage(
+                contentFilter: filter,
+                configuration: configuration
+            )
+        } catch {
+            throw ShotdeckError.captureFailed(underlying: error.localizedDescription)
+        }
+
+        let data = NSMutableData()
+        guard let dest = CGImageDestinationCreateWithData(
+            data,
+            UTType.png.identifier as CFString,
+            1,
+            nil
+        ) else {
+            throw ShotdeckError.captureFailed(underlying: "could not create PNG image destination")
+        }
+        CGImageDestinationAddImage(dest, cgImage, nil)
+        guard CGImageDestinationFinalize(dest) else {
+            throw ShotdeckError.captureFailed(underlying: "PNG encoding failed to finalize")
+        }
+
+        return CapturedImage(
+            pngData: data as Data,
+            pixelWidth: cgImage.width,
+            pixelHeight: cgImage.height,
+            scale: scale
+        )
+    }
+}