Make sure user knows what they're picking

Abort selection until *some* kind of asset has been downloaded.

// FREEBIE

Signal/src/ViewControllers/GifPicker/GifPickerCell.swift

@@ -35,6 +35,14 @@ class GifPickerCell: UICollectionViewCell {
     var animatedAssetRequest: GiphyAssetRequest?
     var animatedAsset: GiphyAsset?
     var imageView: YYAnimatedImageView?
+    var activityIndicator: UIActivityIndicatorView?
+
+    var isCellSelected: Bool = false {
+        didSet {
+            AssertIsOnMainThread()
+            ensureCellState()
+        }
+    }
 
     // As another bandwidth saving measure, we only fetch the full sized GIF when the user selects it.
     private var renditionForSending: GiphyRendition?
@@ -59,6 +67,8 @@ class GifPickerCell: UICollectionViewCell {
         animatedAssetRequest = nil
         imageView?.removeFromSuperview()
         imageView = nil
+        activityIndicator = nil
+        isCellSelected = false
     }
 
     private func clearStillAssetRequest() {
@@ -202,6 +212,24 @@ class GifPickerCell: UICollectionViewCell {
         }
         imageView.image = image
         self.backgroundColor = nil
+
+        if self.isCellSelected {
+            let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .gray)
+            self.activityIndicator = activityIndicator
+            addSubview(activityIndicator)
+            activityIndicator.autoCenterInSuperview()
+            activityIndicator.startAnimating()
+
+            // Render activityIndicator on a white tile to ensure it's visible on
+            // when overalayed on a variety of potential gifs.
+            activityIndicator.backgroundColor = UIColor.white.withAlphaComponent(0.3)
+            activityIndicator.autoSetDimension(.width, toSize: 30)
+            activityIndicator.autoSetDimension(.height, toSize: 30)
+            activityIndicator.layer.cornerRadius = 3
+        } else {
+            self.activityIndicator?.stopAnimating()
+            self.activityIndicator = nil
+        }
     }
 
     public func requestRenditionForSending() -> Promise<GiphyAsset> {

Signal/src/ViewControllers/GifPicker/GifPickerViewController.swift

@@ -293,6 +293,12 @@ class GifPickerViewController: OWSViewController, UISearchBarDelegate, UICollect
             return
         }
 
+        guard cell.stillAsset != nil || cell.animatedAsset != nil else {
+            // we don't want to let the user blindly select a gray cell
+            Logger.debug("\(TAG) ignoring selection of cell with no preview")
+            return
+        }
+
         guard self.selectedCell == nil else {
             owsFail("\(TAG) Already selected cell")
             return
@@ -302,13 +308,9 @@ class GifPickerViewController: OWSViewController, UISearchBarDelegate, UICollect
         // Fade out all cells except the selected one.
         let maskingView = OWSBezierPathView()
         self.view.addSubview(maskingView)
-
-        maskingView.configureShapeLayerBlock = { [weak self] layer, bounds in
-            guard let strongSelf = self else {
-                return
-            }
+        let cellRect = self.collectionView.convert(cell.frame, to: self.view)
+        maskingView.configureShapeLayerBlock = { layer, bounds in
             let path = UIBezierPath(rect: bounds)
-            let cellRect = strongSelf.collectionView.convert(cell.frame, to: strongSelf.view)
             path.append(UIBezierPath(rect: cellRect))
 
             layer.path = path.cgPath
@@ -318,19 +320,7 @@ class GifPickerViewController: OWSViewController, UISearchBarDelegate, UICollect
         }
         maskingView.autoPinEdgesToSuperviewEdges()
 
-        let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .gray)
-        cell.contentView.addSubview(activityIndicator)
-        activityIndicator.autoCenterInSuperview()
-
-        activityIndicator.startAnimating()
-
-        // Render activityIndicator on a white tile to ensure it's visible on
-        // when overalayed on a variety of potential gifs.
-        activityIndicator.backgroundColor = UIColor.white.withAlphaComponent(0.3)
-        activityIndicator.autoSetDimension(.width, toSize: 30)
-        activityIndicator.autoSetDimension(.height, toSize: 30)
-        activityIndicator.layer.cornerRadius = 3
-
+        cell.isCellSelected = true
         self.collectionView.isUserInteractionEnabled = false
 
         getFileForCell(cell)