Use narrow change events in image editor.

SignalMessaging/Views/ImageEditor/ImageEditorModel.swift

@@ -139,6 +139,10 @@ public class OrderedDictionary<ValueType>: NSObject {
         return OrderedDictionary(keyValueMap: keyValueMap, orderedKeys: orderedKeys)
     }
 
+    public func value(forKey key: KeyType) -> ValueType? {
+        return keyValueMap[key]
+    }
+
     public func append(key: KeyType, value: ValueType) {
         if keyValueMap[key] != nil {
             owsFailDebug("Unexpected duplicate key in key map: \(key)")
@@ -239,6 +243,11 @@ public class ImageEditorContents: NSObject {
         return ImageEditorContents(itemMap: itemMap.clone())
     }
 
+    @objc
+    public func item(forId itemId: String) -> ImageEditorItem? {
+        return itemMap.value(forKey: itemId)
+    }
+
     @objc
     public func append(item: ImageEditorItem) {
         Logger.verbose("\(item.itemId)")
@@ -300,6 +309,7 @@ private class ImageEditorOperation: NSObject {
 @objc
 public protocol ImageEditorModelDelegate: class {
     func imageEditorModelDidChange()
+    func imageEditorModelDidChange(changedItemIds: [String])
 }
 
 // MARK: -
@@ -360,6 +370,11 @@ public class ImageEditorModel: NSObject {
         return contents.items()
     }
 
+    @objc
+    public func item(forId itemId: String) -> ImageEditorItem? {
+        return contents.item(forId: itemId)
+    }
+
     @objc
     public func canUndo() -> Bool {
         return !undoStack.isEmpty
@@ -382,6 +397,7 @@ public class ImageEditorModel: NSObject {
 
         self.contents = undoOperation.contents
 
+        // We could diff here and yield a more narrow change event.
         delegate?.imageEditorModelDidChange()
     }
 
@@ -397,6 +413,7 @@ public class ImageEditorModel: NSObject {
 
         self.contents = redoOperation.contents
 
+        // We could diff here and yield a more narrow change event.
         delegate?.imageEditorModelDidChange()
     }
 
@@ -404,7 +421,7 @@ public class ImageEditorModel: NSObject {
     public func append(item: ImageEditorItem) {
         performAction({ (newContents) in
             newContents.append(item: item)
-        })
+        }, changedItemIds: [item.itemId])
     }
 
     @objc
@@ -420,10 +437,11 @@ public class ImageEditorModel: NSObject {
     public func remove(item: ImageEditorItem) {
         performAction({ (newContents) in
             newContents.remove(item: item)
-        })
+        }, changedItemIds: [item.itemId])
     }
 
     private func performAction(_ action: (ImageEditorContents) -> Void,
+                               changedItemIds: [String],
                                suppressUndo: Bool = false) {
         if !suppressUndo {
             let undoOperation = ImageEditorOperation(contents: contents)
@@ -435,6 +453,6 @@ public class ImageEditorModel: NSObject {
         action(newContents)
         contents = newContents
 
-        delegate?.imageEditorModelDidChange()
+        delegate?.imageEditorModelDidChange(changedItemIds: changedItemIds)
     }
 }

SignalMessaging/Views/ImageEditor/ImageEditorView.swift

@@ -101,8 +101,6 @@ public class ImageEditorView: UIView, ImageEditorModelDelegate {
     public func handleTouchGesture(_ gestureRecognizer: UIGestureRecognizer) {
         AssertIsOnMainThread()
 
-        Logger.verbose("\(NSStringForUIGestureRecognizerState(gestureRecognizer.state))")
-
         let removeCurrentStroke = {
             if let stroke = self.currentStroke {
                 self.model.remove(item: stroke)
@@ -163,13 +161,17 @@ public class ImageEditorView: UIView, ImageEditorModelDelegate {
     // MARK: - ImageEditorModelDelegate
 
     public func imageEditorModelDidChange() {
-        // TODO: We eventually want to narrow our change events
-        // to reflect the specific item(s) which changed.
         updateAllContent()
 
         updateButtons()
     }
 
+    public func imageEditorModelDidChange(changedItemIds: [String]) {
+        updateContent(changedItemIds: changedItemIds)
+
+        updateButtons()
+    }
+
     // MARK: - Accessor Overrides
 
     @objc public override var bounds: CGRect {
@@ -190,33 +192,71 @@ public class ImageEditorView: UIView, ImageEditorModelDelegate {
 
     // MARK: - Content
 
-    var contentLayers = [CALayer]()
+    var contentLayerMap = [String: CALayer]()
 
     internal func updateAllContent() {
         AssertIsOnMainThread()
 
-        for layer in contentLayers {
+        // Don't animate changes.
+        CATransaction.begin()
+        CATransaction.setDisableActions(true)
+
+        for layer in contentLayerMap.values {
             layer.removeFromSuperlayer()
         }
-        contentLayers.removeAll()
+        contentLayerMap.removeAll()
 
-        guard bounds.width > 0,
-            bounds.height > 0 else {
-                return
+        if bounds.width > 0,
+            bounds.height > 0 {
+
+            for item in model.items() {
+                guard let layer = ImageEditorView.layerForItem(item: item,
+                                                               viewSize: bounds.size) else {
+                                                                continue
+                }
+
+                self.layer.addSublayer(layer)
+                contentLayerMap[item.itemId] = layer
+            }
         }
 
+        CATransaction.commit()
+    }
+
+    internal func updateContent(changedItemIds: [String]) {
+        AssertIsOnMainThread()
+
         // Don't animate changes.
         CATransaction.begin()
         CATransaction.setDisableActions(true)
 
-        for item in model.items() {
-            guard let layer = ImageEditorView.layerForItem(item: item,
-                                                           viewSize: bounds.size) else {
-                continue
+        // Remove all changed items.
+        for itemId in changedItemIds {
+            if let layer = contentLayerMap[itemId] {
+                layer.removeFromSuperlayer()
             }
+            contentLayerMap.removeValue(forKey: itemId)
+        }
+
+        if bounds.width > 0,
+            bounds.height > 0 {
 
-            self.layer.addSublayer(layer)
-            contentLayers.append(layer)
+            // Create layers for inserted and updated items.
+            for itemId in changedItemIds {
+                guard let item = model.item(forId: itemId) else {
+                    // Item was deleted.
+                    continue
+                }
+
+                // Item was inserted or updated.
+                guard let layer = ImageEditorView.layerForItem(item: item,
+                                                               viewSize: bounds.size) else {
+                                                                continue
+                }
+
+                self.layer.addSublayer(layer)
+                contentLayerMap[item.itemId] = layer
+            }
         }
 
         CATransaction.commit()