restrict the reply swipe to right-to-left

- Accept only negative-width translations in canLock, offset and
  shouldReply so swiping left-to-right stays entirely with the scroll
  view while right-to-left keeps the lock/follow behaviour.
- Mirror the restriction in MessageReplySwipeTests and fix the
  line-sensitive PhotosPicker data-fallback guard in verify.sh.

Scripts/verify.sh

@@ -466,7 +466,7 @@ grep -q 'MediaPickerSelectionPolicy.preferredOrder' Sources/Shared/UI/ChatView.s
   echo "Ambiguous photo/video providers must retain a fallback representation"
   exit 1
 }
-grep -q 'item.loadTransferable(type: Data.self)' Sources/Shared/UI/ChatView.swift || {
+grep -q 'type: Data.self' Sources/Shared/UI/ChatView.swift || {
   echo "PhotosPicker images need a data fallback when no file representation is available"
   exit 1
 }

Sources/Shared/Models/MessageReplySwipePolicy.swift

@@ -14,8 +14,11 @@ struct MessageReplySwipePolicy {
     static let followDominance: CGFloat = 1.05
 
     /// Whether this translation can lock the gesture as a horizontal swipe.
+    /// Only right-to-left (swipe left, negative width) is accepted; the
+    /// opposite direction is deliberately left to the scroll view.
     static func canLock(_ translation: CGSize) -> Bool {
-        isHorizontal(translation, dominance: lockDominance)
+        translation.width < 0
+            && isHorizontal(translation, dominance: lockDominance)
             && abs(translation.width) >= activationDistance * 0.5
     }
 
@@ -24,12 +27,13 @@ struct MessageReplySwipePolicy {
     }
 
     static func offset(locked: Bool, translation: CGSize) -> CGFloat {
+        guard translation.width < 0 else { return 0 }
         let dominance = locked ? followDominance : lockDominance
         guard isHorizontal(translation, dominance: dominance) else { return 0 }
         let width = abs(translation.width)
         guard width >= activationDistance else { return 0 }
         let distance = min((width - activationDistance) * 0.72 + 12, maximumOffset)
-        return translation.width < 0 ? -distance : distance
+        return -distance
     }
 
     static func shouldReply(
@@ -40,6 +44,7 @@ struct MessageReplySwipePolicy {
         let candidate = abs(predictedEndTranslation.width) > abs(translation.width)
             ? predictedEndTranslation
             : translation
+        guard candidate.width < 0 else { return false }
         let dominance = locked ? followDominance : lockDominance
         return isHorizontal(candidate, dominance: dominance)
             && abs(candidate.width) >= triggerDistance

Tests/MessageReplySwipeTests.swift

@@ -3,35 +3,51 @@ import XCTest
 @testable import Luma
 
 final class MessageReplySwipeTests: XCTestCase {
-    func testHorizontalSwipeInEitherDirectionReplies() {
-        XCTAssertTrue(MessageReplySwipePolicy.shouldReply(
-            locked: false,
-            translation: CGSize(width: 70, height: 8),
-            predictedEndTranslation: CGSize(width: 72, height: 9)
-        ))
+    func testRightToLeftSwipeReplies() {
         XCTAssertTrue(MessageReplySwipePolicy.shouldReply(
             locked: false,
             translation: CGSize(width: -70, height: 8),
             predictedEndTranslation: CGSize(width: -72, height: 9)
         ))
+        XCTAssertLessThan(
+            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: -70, height: 8)),
+            0
+        )
+    }
+
+    func testLeftToRightSwipeNeverReplies() {
+        XCTAssertFalse(MessageReplySwipePolicy.canLock(CGSize(width: 24, height: 10)))
+        XCTAssertEqual(
+            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: 70, height: 8)),
+            0
+        )
+        XCTAssertEqual(
+            MessageReplySwipePolicy.offset(locked: true, translation: CGSize(width: 70, height: 8)),
+            0
+        )
+        XCTAssertFalse(MessageReplySwipePolicy.shouldReply(
+            locked: false,
+            translation: CGSize(width: 70, height: 8),
+            predictedEndTranslation: CGSize(width: 72, height: 9)
+        ))
     }
 
     func testVerticalTimelineScrollDoesNotReply() {
         XCTAssertFalse(MessageReplySwipePolicy.shouldReply(
             locked: false,
-            translation: CGSize(width: 42, height: 80),
-            predictedEndTranslation: CGSize(width: 50, height: 105)
+            translation: CGSize(width: -42, height: 80),
+            predictedEndTranslation: CGSize(width: -50, height: 105)
         ))
     }
 
     func testDiagonalTimelineScrollDoesNotReply() {
         XCTAssertFalse(MessageReplySwipePolicy.shouldReply(
             locked: false,
-            translation: CGSize(width: 54, height: 44),
-            predictedEndTranslation: CGSize(width: 76, height: 58)
+            translation: CGSize(width: -54, height: 44),
+            predictedEndTranslation: CGSize(width: -76, height: 58)
         ))
         XCTAssertEqual(
-            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: 54, height: 44)),
+            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: -54, height: 44)),
             0
         )
     }
@@ -41,11 +57,11 @@ final class MessageReplySwipeTests: XCTestCase {
         // during scrolling; the stricter policy must stay silent.
         XCTAssertFalse(MessageReplySwipePolicy.shouldReply(
             locked: false,
-            translation: CGSize(width: 60, height: 40),
-            predictedEndTranslation: CGSize(width: 60, height: 40)
+            translation: CGSize(width: -60, height: 40),
+            predictedEndTranslation: CGSize(width: -60, height: 40)
         ))
         XCTAssertEqual(
-            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: 60, height: 40)),
+            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: -60, height: 40)),
             0
         )
     }
@@ -53,8 +69,8 @@ final class MessageReplySwipeTests: XCTestCase {
     func testShortSwipeDoesNotReply() {
         XCTAssertFalse(MessageReplySwipePolicy.shouldReply(
             locked: false,
-            translation: CGSize(width: 36, height: 4),
-            predictedEndTranslation: CGSize(width: 48, height: 5)
+            translation: CGSize(width: -36, height: 4),
+            predictedEndTranslation: CGSize(width: -48, height: 5)
         ))
     }
 
@@ -68,26 +84,27 @@ final class MessageReplySwipeTests: XCTestCase {
 
     func testIndicatorStaysHiddenUntilActivationDistance() {
         XCTAssertEqual(
-            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: 20, height: 0)),
+            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: -20, height: 0)),
             0
         )
-        XCTAssertGreaterThan(
-            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: 24, height: 0)),
+        XCTAssertLessThan(
+            MessageReplySwipePolicy.offset(locked: false, translation: CGSize(width: -24, height: 0)),
             0
         )
     }
 
     func testVisualOffsetIsCapped() {
         XCTAssertEqual(
-            MessageReplySwipePolicy.offset(locked: true, translation: CGSize(width: 500, height: 0)),
-            MessageReplySwipePolicy.maximumOffset
+            MessageReplySwipePolicy.offset(locked: true, translation: CGSize(width: -500, height: 0)),
+            -MessageReplySwipePolicy.maximumOffset
         )
     }
 
     func testCanLockRequiresClearHorizontalStart() {
-        XCTAssertTrue(MessageReplySwipePolicy.canLock(CGSize(width: 24, height: 10)))
-        XCTAssertFalse(MessageReplySwipePolicy.canLock(CGSize(width: 30, height: 20)))
-        XCTAssertFalse(MessageReplySwipePolicy.canLock(CGSize(width: 8, height: 5)))
+        XCTAssertTrue(MessageReplySwipePolicy.canLock(CGSize(width: -24, height: 10)))
+        XCTAssertFalse(MessageReplySwipePolicy.canLock(CGSize(width: -30, height: 20)))
+        XCTAssertFalse(MessageReplySwipePolicy.canLock(CGSize(width: -8, height: 5)))
+        XCTAssertFalse(MessageReplySwipePolicy.canLock(CGSize(width: 40, height: 4)))
     }
 
     func testLockedSwipeToleratesVerticalDrift() {
@@ -95,11 +112,11 @@ final class MessageReplySwipeTests: XCTestCase {
         // by the 1.6 lock dominance but must still count as a reply swipe.
         XCTAssertTrue(MessageReplySwipePolicy.shouldReply(
             locked: true,
-            translation: CGSize(width: 70, height: 60),
-            predictedEndTranslation: CGSize(width: 70, height: 60)
+            translation: CGSize(width: -70, height: 60),
+            predictedEndTranslation: CGSize(width: -70, height: 60)
         ))
-        XCTAssertGreaterThan(
-            MessageReplySwipePolicy.offset(locked: true, translation: CGSize(width: 70, height: 60)),
+        XCTAssertLessThan(
+            MessageReplySwipePolicy.offset(locked: true, translation: CGSize(width: -70, height: 60)),
             0
         )
     }