Fix profile tab switching animation ending in bad state

Caused by fda0c18794, old/new.view is no
longer the same as .collectionView, so the transform wasn't being
properly reset.

Closes #536

Tusker/Screens/Profile/ProfileHeaderCollectionViewCell.swift

@@ -63,11 +63,18 @@ class ProfileHeaderCollectionViewCell: UICollectionViewCell {
         }
     }
     
-    // overrides an internal method
-    // when the super impl is used, preferredLayoutAttributesFitting(_:) isn't called while the view is offscreen (i.e., window == nil)
-    // and so the collection view imposes a height of 44pts which breaks the layout
-    @objc func _preferredLayoutAttributesFittingAttributes(_ attributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
-        return preferredLayoutAttributesFitting(attributes)
+    override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
+        switch state {
+        case .unloaded:
+            return super.preferredLayoutAttributesFitting(layoutAttributes)
+        case .placeholder(let heightConstraint):
+            layoutAttributes.size.height = heightConstraint.constant
+            return layoutAttributes
+        case .view(let profileHeaderView):
+            let size = profileHeaderView.systemLayoutSizeFitting(layoutAttributes.size, withHorizontalFittingPriority: .required, verticalFittingPriority: .fittingSizeLevel)
+            layoutAttributes.size = size
+            return layoutAttributes
+        }
     }
     
     enum State {

Tusker/Screens/Profile/ProfileViewController.swift

@@ -213,7 +213,7 @@ class ProfileViewController: UIViewController, StateRestorableViewController {
         
         // old header cell must have the header view
         let headerView = oldHeaderCell.addConstraint(height: oldHeaderCell.bounds.height)!
-        // Set the outgoing VC's header view mode to placeholder, so that it does steal the header view back
+        // Set the outgoing VC's header view mode to placeholder, so that it does not steal the header view back
         // in case it updates the cell in the background.
         old.headerViewMode = .placeholder(height: oldHeaderCell.bounds.height)
         
@@ -224,12 +224,13 @@ class ProfileViewController: UIViewController, StateRestorableViewController {
         }
         
         // disable user interaction during animation, to avoid any potential weird race conditions
-        headerView.isUserInteractionEnabled = false
+        view.isUserInteractionEnabled = false
+        
         headerView.layer.zPosition = 100
         view.addSubview(headerView)
         let oldHeaderCellTop = oldHeaderCell.convert(CGPoint.zero, to: view).y
         let headerTopOffset = oldHeaderCellTop - view.safeAreaInsets.top
-        let headerBottomOffset = oldHeaderCell.convert(CGPoint(x: 0, y: oldHeaderCell.bounds.maxY), to: view).y// - view.safeAreaInsets.top
+        let headerBottomOffset = oldHeaderCell.convert(CGPoint(x: 0, y: oldHeaderCell.bounds.maxY), to: view).y
         NSLayoutConstraint.activate([
             headerView.topAnchor.constraint(equalTo: view.topAnchor, constant: headerTopOffset),
             headerView.bottomAnchor.constraint(equalTo: view.topAnchor, constant: headerBottomOffset),
@@ -272,16 +273,17 @@ class ProfileViewController: UIViewController, StateRestorableViewController {
             }
             animator.addCompletion { _ in
                 old.removeViewAndController()
-                old.collectionView.transform = .identity
+                old.view.transform = .identity
                 
-                new.collectionView.transform = .identity
+                new.view.transform = .identity
                 new.collectionView.contentOffset = origOldContentOffset
                 
                 // reenable scroll indicators after the switching animation is done
                 old.collectionView.showsVerticalScrollIndicator = true
                 new.collectionView.showsVerticalScrollIndicator = true
                 
-                headerView.isUserInteractionEnabled = true
+                self.view.isUserInteractionEnabled = true
+                
                 headerView.transform = .identity
                 headerView.layer.zPosition = 0
                 // move the header view into the new page controller's cell