fix: Session replay masking not working inside scroll view (#4498)

Fixed calculation of scroll view children position for masking

Author: brustolin

CHANGELOG.md

@@ -29,6 +29,10 @@
 
 - Masking text with transparent text color (#4499)
 
+### Fixes
+
+- Session replay masking not working inside scroll view (#4498)
+
 ## 8.39.0
 
 ### Removal of Experimental API

Samples/iOS-Swift/iOS-Swift/ViewControllers/TableViewController.swift

@@ -36,6 +36,7 @@ class TableViewController: UITableViewController {
 
         let w = 1.0 - (Double(indexPath.row) / 99)
         cell.backgroundColor = UIColor(white: CGFloat(w), alpha: 1)
+        cell.textLabel?.text = "Row #\(indexPath.row)"
 
         return cell
     }

Sources/Swift/Tools/UIRedactBuilder.swift

@@ -158,9 +158,9 @@ class UIRedactBuilder {
         var redactingRegions = [RedactRegion]()
 
         self.mapRedactRegion(fromView: view,
+                             relativeTo: nil,
                              redacting: &redactingRegions,
-                             rootFrame: view.frame,
-                             transform: CGAffineTransform.identity)
+                             rootFrame: view.frame)
 
         var swiftUIRedact = [RedactRegion]()
         var otherRegions = [RedactRegion]()
@@ -198,12 +198,12 @@ class UIRedactBuilder {
         return image.imageAsset?.value(forKey: "_containingBundle") == nil
     }
 
-    private func mapRedactRegion(fromView view: UIView, redacting: inout [RedactRegion], rootFrame: CGRect, transform: CGAffineTransform, forceRedact: Bool = false) {
+    private func mapRedactRegion(fromView view: UIView, relativeTo parentLayer: CALayer?, redacting: inout [RedactRegion], rootFrame: CGRect, forceRedact: Bool = false) {
         guard !redactClassesIdentifiers.isEmpty && !view.isHidden && view.alpha != 0 else { return }
 
         let layer = view.layer.presentation() ?? view.layer
 
-        let newTransform = concatenateTranform(transform, with: layer)
+        let newTransform = getTranform(from: layer, withParent: parentLayer)
 
         let ignore = !forceRedact && shouldIgnore(view: view)
         let swiftUI = SentryRedactViewHelper.shouldRedactSwiftUI(view)
@@ -233,23 +233,24 @@ class UIRedactBuilder {
             redacting.append(RedactRegion(size: layer.bounds.size, transform: newTransform, type: .clipEnd))
         }
         for subview in view.subviews.sorted(by: { $0.layer.zPosition < $1.layer.zPosition }) {
-            mapRedactRegion(fromView: subview, redacting: &redacting, rootFrame: rootFrame, transform: newTransform, forceRedact: enforceRedact)
+            mapRedactRegion(fromView: subview, relativeTo: layer, redacting: &redacting, rootFrame: rootFrame, forceRedact: enforceRedact)
         }
         if view.clipsToBounds {
             redacting.append(RedactRegion(size: layer.bounds.size, transform: newTransform, type: .clipBegin))
         }
     }
-    
+
     /**
-     Apply the layer transformation and position to given transformation.
+     Gets a transform that represents the layer global position.
      */
-    private func concatenateTranform(_ transform: CGAffineTransform, with layer: CALayer) -> CGAffineTransform {
+    private func getTranform(from layer: CALayer, withParent parentLayer: CALayer?) -> CGAffineTransform {
         let size = layer.bounds.size
-        let layerMiddle = CGPoint(x: size.width * layer.anchorPoint.x, y: size.height * layer.anchorPoint.y)
-        
-        var newTransform = transform.translatedBy(x: layer.position.x, y: layer.position.y)
+        let anchorPoint = CGPoint(x: size.width * layer.anchorPoint.x, y: size.height * layer.anchorPoint.y)
+        let position = parentLayer?.convert(layer.position, to: nil) ?? layer.position
+
+        var newTransform = CGAffineTransform(translationX: position.x, y: position.y)
         newTransform = CATransform3DGetAffineTransform(layer.transform).concatenating(newTransform)
-        return newTransform.translatedBy(x: -layerMiddle.x, y: -layerMiddle.y)
+        return newTransform.translatedBy(x: -anchorPoint.x, y: -anchorPoint.y)
     }
 
     /**

Tests/SentryTests/SentryViewPhotographerTests.swift

@@ -195,6 +195,21 @@ class SentryViewPhotographerTests: XCTestCase {
         assertColor(pixel1, .green)
     }
 
+    func testLabelInsideScrollView() throws {
+        let label1 = UILabel(frame: CGRect(x: 0, y: 25, width: 50, height: 25))
+        label1.text = "Test"
+        label1.textColor = .green
+        
+        let scrollView = UIScrollView(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
+        scrollView.addSubview(label1)
+        scrollView.contentOffset = CGPoint(x: 0, y: 25)
+        
+        let image = try XCTUnwrap(prepare(views: [scrollView]))
+        let pixel1 = color(at: CGPoint(x: 10, y: 10), in: image)
+        
+        assertColor(pixel1, .green)
+    }
+    
     private func assertColor(_ color1: UIColor, _ color2: UIColor) {
         let sRGBColor1 = color1.cgColor.converted(to: CGColorSpace(name: CGColorSpace.sRGB)!, intent: .defaultIntent, options: nil)
         let sRGBColor2 = color2.cgColor.converted(to: CGColorSpace(name: CGColorSpace.sRGB)!, intent: .defaultIntent, options: nil)