Fix vertical offset when capturing the secondary display

The first ScreenCaptureKit Y-flip used the wrong reference edges, shifting
cropped selections on displays below the main screen. Convert each selection
per-display as scY = appKitY - NSScreen.maxY + SCDisplay.maxY, which
matches both the main and secondary displays.

💘 Generated with Crush

Assisted-by: Crush:deepseek-v4-flash-0731

Sources/Kapture/App.swift

@@ -48,6 +48,13 @@ struct MenuView: View {
 
         Divider()
 
+        Button("Copy Diagnostics") {
+            let diag = CaptureController.shared.diagnostics()
+            let pasteboard = NSPasteboard.general
+            pasteboard.clearContents()
+            pasteboard.setString(diag, forType: .string)
+        }
+
         Button(LoginItem.isEnabled ? "Disable Launch at Login" : "Launch at Login") {
             if !LoginItem.toggle() {
                 let alert = NSAlert()

Sources/Kapture/CaptureController.swift

@@ -10,6 +10,38 @@ final class CaptureController: NSObject {
     private var previousApp: NSRunningApplication?
     private var overlayIDs: [Int] = []
 
+    /// Diagnostic snapshot for "Copy Diagnostics" menu item.
+    func diagnostics() -> String {
+        var lines: [String] = []
+        lines.append("Kapture diagnostics")
+        for (i, s) in NSScreen.screens.enumerated() {
+            let scale = s.backingScaleFactor
+            let cgID = (s.deviceDescription[NSDeviceDescriptionKey("NSScreenNumber")] as? NSNumber)?.uint32Value ?? 0
+            lines.append("screen[\(i)]: frame=\(s.frame) scale=\(scale) backingSize=\(s.frame.width*scale)x\(s.frame.height*scale) cgID=\(cgID)")
+        }
+        if #available(macOS 14.0, *) {
+            Task {
+                if let content = try? await SCShareableContent.current {
+                    for (i, d) in content.displays.enumerated() {
+                        lines.append("SCDisplay[\(i)]: frame=\(d.frame) width=\(d.width)x\(d.height) id=\(d.displayID)")
+                    }
+                } else {
+                    lines.append("SCShareableContent: unavailable (no Screen Recording permission?)")
+                }
+                let text = lines.joined(separator: "\n")
+                let pb = NSPasteboard.general
+                pb.clearContents()
+                pb.setString(text, forType: .string)
+            }
+        } else {
+            let text = lines.joined(separator: "\n")
+            let pb = NSPasteboard.general
+            pb.clearContents()
+            pb.setString(text, forType: .string)
+        }
+        return lines.joined(separator: "\n")
+    }
+
     func begin() {
         guard !isSelecting else { return }
         guard PermissionManager.isGranted else {
@@ -85,19 +117,13 @@ final class ScreenCapture {
     private init() {}
 
     @available(macOS 14.0, *)
-    private func crop(_ image: CGImage, to rect: NSRect, display: SCDisplay) -> CGImage? {
-        // The captured image may be at any scale (retina 2x, secondary display
-        // 1x, or trimmed by ScreenCaptureKit). Derive the pixel scale from the
-        // image we actually got, relative to the display's point frame.
+    private func crop(_ image: CGImage, to cgRect: CGRect, display: SCDisplay) -> CGImage? {
+        // cgRect is already in SCDisplay space (Y flipped relative to AppKit).
+        // Derive the pixel scale from the image we actually got, relative to
+        // the display's point frame.
         let scaleX = CGFloat(image.width) / display.frame.width
         let scaleY = CGFloat(image.height) / display.frame.height
         guard scaleX > 0, scaleY > 0 else { return nil }
-        let cgRect = CGRect(
-            x: rect.minX,
-            y: rect.minY,
-            width: rect.width,
-            height: rect.height
-        )
         let pxRect = CGRect(
             x: (cgRect.minX - display.frame.minX) * scaleX,
             y: (cgRect.minY - display.frame.minY) * scaleY,
@@ -145,18 +171,30 @@ final class ScreenCapture {
                 // width/height are output PIXELS. Multiply by the backing scale
                 // of the screen containing the selection so retina displays are
                 // captured at full resolution and 1x displays stay 1x.
-                let backingScale = NSScreen.screens
-                    .first(where: { $0.frame.contains(NSPoint(x: rect.midX, y: rect.midY)) })?
-                    .backingScaleFactor ?? 1
+                guard let screen = NSScreen.screens.first(where: { $0.frame.contains(NSPoint(x: rect.midX, y: rect.midY)) }) else {
+                    completion(nil)
+                    return
+                }
+                let backingScale = screen.backingScaleFactor
                 config.width = Int(CGFloat(display.width) * backingScale)
                 config.height = Int(CGFloat(display.height) * backingScale)
                 config.showsCursor = true
 
+                // ScreenCaptureKit uses a different origin than AppKit for
+                // screens stacked around the main display: per-display,
+                // SCDisplay y = appKitY - NSScreen.maxY + SCDisplay.maxY.
+                let scRect = CGRect(
+                    x: rect.minX,
+                    y: rect.minY - screen.frame.maxY + display.frame.maxY,
+                    width: rect.width,
+                    height: rect.height
+                )
+
                 guard let image = try? await SCScreenshotManager.captureImage(contentFilter: filter, configuration: config) else {
                     completion(nil)
                     return
                 }
-                completion(self.crop(image, to: rect, display: display))
+                completion(self.crop(image, to: scRect, display: display))
             }
         } else {
             guard let primary = NSScreen.screens.first(where: { $0.frame.origin == .zero }) ?? NSScreen.screens.first else {

build-app.sh

@@ -108,9 +108,9 @@ cat > "$APP/Contents/Info.plist" <<'PLIST'
     <key>CFBundleIconFile</key>
     <string>Icon</string>
     <key>CFBundleShortVersionString</key>
-    <string>1.1.5</string>
+    <string>1.1.8</string>
     <key>CFBundleVersion</key>
-    <string>15</string>
+    <string>18</string>
     <key>LSUIElement</key>
     <true/>
     <key>NSHighResolutionCapable</key>