Merge branch 'mkirk/scroll-to-bottom-when-switching-albums'

Signal/src/ViewControllers/PhotoLibrary/ImagePickerController.swift

@@ -116,13 +116,14 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
 
         reloadDataAndRestoreSelection()
         if !hasEverAppeared {
-            hasEverAppeared = true
             scrollToBottom(animated: false)
         }
     }
 
     override func viewDidAppear(_ animated: Bool) {
         super.viewDidAppear(animated)
+
+        hasEverAppeared = true
         // done button may have been disable from the last time we hit "Done"
         // make sure to re-enable it if appropriate upon returning to the view
         hasPressedDoneSinceAppeared = false
@@ -156,8 +157,21 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
             return
         }
 
-        let verticalOffset: CGFloat
+        var verticalOffset: CGFloat
+
+        let visibleHeight = collectionView.bounds.height - collectionView.contentInset.top
+        let contentHeight = collectionView.contentSize.height
+        if contentHeight <= visibleHeight {
+            verticalOffset = -collectionView.contentInset.top
+        } else {
+            let topOfLastPage = contentHeight - collectionView.bounds.height
+            verticalOffset = topOfLastPage
+        }
+
         if #available(iOS 11, *) {
+            if hasEverAppeared {
+                verticalOffset += collectionView.safeAreaInsets.bottom
+            } else {
                 // On iOS10 and earlier, we can be precise, but as of iOS11 `collectionView.contentInset`
                 // is based on `safeAreaInsets`, which isn't accurate until `viewDidAppear` at the earliest.
                 //
@@ -168,19 +182,12 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
                 // Overshooting like this works without visible animation glitch. on iOS11+
                 // However, before iOS11, "overshooting" the contentOffset like this produces a broken
                 // layout or hanging. Luckily for those versions, before the safeAreaInset feature
-            // existed, we can accurately accesse colletionView.contentInset before `viewDidAppear`
+                // existed, we can accurately access collectionView.contentInset before `viewDidAppear`
                 // and calculate a precise content offset.
-            verticalOffset = CGFloat.greatestFiniteMagnitude
-        } else {
-            let visibleHeight = collectionView.bounds.height - collectionView.contentInset.top
-            let contentHeight = collectionView.contentSize.height
-            if contentHeight <= visibleHeight {
-                verticalOffset = -collectionView.contentInset.top
-            } else {
-                let topOfLastPage = contentHeight - collectionView.bounds.height
-                verticalOffset = topOfLastPage
+                verticalOffset += 122
             }
         }
+
         collectionView.setContentOffset(CGPoint(x: 0, y: verticalOffset), animated: animated)
     }
 
@@ -478,6 +485,7 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
         }
 
         collectionView?.reloadData()
+        scrollToBottom(animated: false)
         hideCollectionPicker()
     }