Clean up brush stroke gesture usage.

SignalMessaging/Views/ImageEditor/ImageEditorBrushViewController.swift

@@ -21,8 +21,6 @@ public class ImageEditorBrushViewController: OWSViewController {
 
     private let paletteView: ImageEditorPaletteView
 
-    private var brushGestureRecognizer: ImageEditorPanGestureRecognizer?
-
     // We only want to let users undo changes made in this view.
     // So we snapshot any older "operation id" and prevent
     // users from undoing it.
@@ -68,8 +66,8 @@ public class ImageEditorBrushViewController: OWSViewController {
         let brushGestureRecognizer = ImageEditorPanGestureRecognizer(target: self, action: #selector(handleBrushGesture(_:)))
         brushGestureRecognizer.maximumNumberOfTouches = 1
         brushGestureRecognizer.referenceView = canvasView.gestureReferenceView
+        brushGestureRecognizer.delegate = self
         self.view.addGestureRecognizer(brushGestureRecognizer)
-        self.brushGestureRecognizer = brushGestureRecognizer
 
         updateNavigationBar()
     }
@@ -171,7 +169,7 @@ public class ImageEditorBrushViewController: OWSViewController {
 
             // Apply the location history of the gesture so that the stroke reflects
             // the touch's movement before the gesture recognized.
-            for location in gestureRecognizer.locations {
+            for location in gestureRecognizer.locationHistory {
                 tryToAppendStrokeSample(location)
             }
 
@@ -230,3 +228,13 @@ extension ImageEditorBrushViewController: ImageEditorPaletteViewDelegate {
         // TODO:
     }
 }
+
+// MARK: -
+
+extension ImageEditorBrushViewController: UIGestureRecognizerDelegate {
+    @objc public func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {
+        // Ignore touches that begin inside the palette.
+        let location = touch.location(in: paletteView)
+        return !paletteView.bounds.contains(location)
+    }
+}

SignalMessaging/Views/ImageEditor/ImageEditorCropViewController.swift

@@ -501,7 +501,7 @@ class ImageEditorCropViewController: OWSViewController {
 
         Logger.verbose("")
 
-        guard let locationStart = gestureRecognizer.locationStart else {
+        guard let locationStart = gestureRecognizer.locationFirst else {
             owsFailDebug("Missing locationStart.")
             return
         }
@@ -666,7 +666,7 @@ class ImageEditorCropViewController: OWSViewController {
             owsFailDebug("Missing pinchTransform.")
             return
         }
-        guard let oldLocationView = gestureRecognizer.locationStart else {
+        guard let oldLocationView = gestureRecognizer.locationFirst else {
             owsFailDebug("Missing locationStart.")
             return
         }
@@ -685,7 +685,7 @@ class ImageEditorCropViewController: OWSViewController {
     }
 
     private func cropRegion(forGestureRecognizer gestureRecognizer: ImageEditorPanGestureRecognizer) -> CropRegion? {
-        guard let location = gestureRecognizer.locationStart else {
+        guard let location = gestureRecognizer.locationFirst else {
             owsFailDebug("Missing locationStart.")
             return nil
         }

SignalMessaging/Views/ImageEditor/ImageEditorPanGestureRecognizer.swift

@@ -14,39 +14,57 @@ public class ImageEditorPanGestureRecognizer: UIPanGestureRecognizer {
     public weak var referenceView: UIView?
 
     // Capture the location history of this gesture.
-    public var locations = [CGPoint]()
+    public var locationHistory = [CGPoint]()
 
-    public var locationStart: CGPoint? {
-        return locations.first
+    public var locationFirst: CGPoint? {
+        return locationHistory.first
     }
 
     // MARK: - Touch Handling
 
     @objc
     public override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
-        super.touchesBegan(touches, with: event)
+        updateLocationHistory(event: event)
 
-        guard let referenceView = referenceView else {
-            owsFailDebug("Missing view")
-            return
-        }
-        locations.append(location(in: referenceView))
+        super.touchesBegan(touches, with: event)
     }
 
     @objc
     public override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
+        updateLocationHistory(event: event)
+
         super.touchesMoved(touches, with: event)
+    }
+
+    @objc
+    public override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent) {
+        updateLocationHistory(event: event)
 
+        super.touchesEnded(touches, with: event)
+    }
+
+    private func updateLocationHistory(event: UIEvent) {
+        guard let touches = event.allTouches,
+            touches.count > 0 else {
+                owsFailDebug("no touches.")
+                return
+        }
         guard let referenceView = referenceView else {
             owsFailDebug("Missing view")
             return
         }
-        locations.append(location(in: referenceView))
+        // Find the centroid.
+        var location = CGPoint.zero
+        for touch in touches {
+            location = location.plus(touch.location(in: referenceView))
+        }
+        location = location.times(CGFloat(1) / CGFloat(touches.count))
+        locationHistory.append(location)
     }
 
     public override func reset() {
         super.reset()
 
-        locations.removeAll()
+        locationHistory.removeAll()
     }
 }

SignalMessaging/Views/ImageEditor/ImageEditorView.swift

@@ -274,7 +274,7 @@ public class ImageEditorView: UIView {
 
         switch gestureRecognizer.state {
         case .began:
-            guard let locationStart = gestureRecognizer.locationStart else {
+            guard let locationStart = gestureRecognizer.locationFirst else {
                 owsFailDebug("Missing locationStart.")
                 return
             }
@@ -294,7 +294,7 @@ public class ImageEditorView: UIView {
             guard let textItem = movingTextItem else {
                 return
             }
-            guard let locationStart = gestureRecognizer.locationStart else {
+            guard let locationStart = gestureRecognizer.locationFirst else {
                 owsFailDebug("Missing locationStart.")
                 return
             }