FIX calulcation of targetOffset

ADD support for animated flag
ADD started with writing Snapshot test - WIP
ADD Snapshot for Snapshot test, but current snapshot is not waht we want

Source/Views/StackViewController.swift

@@ -85,7 +85,7 @@ final class StackViewController: UIViewController {
     ///     the stackViews' orientation some relativePosition values have different meaning: 
     ///     beginning - top/left, end - bottom/right
     public func scrollToViewController(target targetViewController: UIViewController,
-                                       position relativePosition: RelativePosition = .center) {
+                                       position relativePosition: RelativePosition = .center, animated: Bool = false) {
 
         guard self.childViewControllers.contains(targetViewController) else {
             return
@@ -95,6 +95,7 @@ final class StackViewController: UIViewController {
         let targetFrame = targetViewController.view.frame
 
         if stackView.axis == .vertical {
+            // keep current horizontal offset
             targetOffset.x = -scrollView.contentInset.left
             let topOffset = targetFrame.origin.y - scrollView.contentInset.top
             let bottomOffset = targetFrame.origin.y + targetFrame.height - scrollView.bounds.height
@@ -104,29 +105,31 @@ final class StackViewController: UIViewController {
                 targetOffset.y = topOffset
                 break
             case .center:
-                targetOffset.y = topOffset - bottomOffset - (targetFrame.height / 2)
+                targetOffset.y = topOffset - (topOffset - bottomOffset) / 2
                 break
             case .end:
                 targetOffset.y = bottomOffset
                 break
             }
         } else {
+            // keep current vertical offset
             targetOffset.y = -scrollView.contentInset.top
+            let leftOffset = targetFrame.origin.x - scrollView.contentInset.left
             let rightOffset = targetFrame.origin.x + targetFrame.width - scrollView.bounds.width
 
             switch relativePosition {
             case .beginning:
-                targetOffset.x = targetFrame.origin.x - scrollView.contentInset.left
+                targetOffset.x = leftOffset
                 break
             case .center:
-                targetOffset.x = -(targetOffset.x - rightOffset - (targetFrame.width / 2))
+                targetOffset.x = leftOffset - (leftOffset - rightOffset) / 2
                 break
             case .end:
                 targetOffset.x = rightOffset
                 break
             }
         }
-        
-        scrollView.setContentOffset(targetOffset, animated: true)
+
+        scrollView.setContentOffset(targetOffset, animated: animated)
     }
 }

Tests/StackClusterTests.swift

@@ -136,6 +136,40 @@ class StackClusterTests: QuickSpec {
                     expect(scrollView).toNot(scroll(.horizontal))
                 }
 
+                context("scroll into view target can be positioned as wanted") {
+                    let size = CGSize(width: 300, height: 300)
+                    let children = [
+                        labelComponent(title: "1", color: .purple, labelSize: size),
+                        labelComponent(title: "2", color: .red, labelSize: size),
+                        labelComponent(title: "3", color: .yellow, labelSize: size),
+                        labelComponent(title: "4", color: .green, labelSize: size),
+                        labelComponent(title: "5", color: .green, labelSize: size)
+                    ]
+
+                    it("should be able to scroll horizontally to target") {
+                        let meta = ClusterLayout.StackConfig(axis: .horizontal)
+                        let vc = stack(with: children, meta: meta)
+                        vc?.loadViewIfNeeded()
+//                        let scrollView = vc?.stackView.superview as? UIScrollView
+                        let targetVC = vc?.childViewControllers[2]
+
+                        // WIP does not scroll at all, with or wothout dispatcher and setting the offset manually in scroll method
+                        let exp = self.expectation(description: "wait for scrolling")
+                        vc?.scrollToViewController(target: targetVC!, position: .center, animated: false)
+
+                        DispatchQueue.main.asyncAfter(deadline: (.now() + 3)) {
+
+                            exp.fulfill()
+                        }
+
+                        self.waitForExpectations(timeout: 5, handler: nil)
+
+//                        expect(vc).to(recordSnapshot())
+//                        expect(scrollView).to(scroll(.horizontal))
+//                        expect(scrollView).toNot(scroll(.vertical))
+                    }
+                }
+
                 context("when a horizontal stack is contained in a vertical stack") {
 
                     let nestedStack: () -> StackViewController? = {