add visible bounds caching by UIElementPath

client/ios/DivKit.xcodeproj/project.pbxproj

@@ -18,6 +18,10 @@
 		4391F7C32A77DB9B006D8818 /* DivViewController+SwiftUI.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4391F7C22A77DB9B006D8818 /* DivViewController+SwiftUI.swift */; };
 		52184FD8296C68E400ECC0E9 /* DivKitExtensions in Frameworks */ = {isa = PBXBuildFile; productRef = 52184FD7296C68E400ECC0E9 /* DivKitExtensions */; };
 		5219194D297B3974007DD5F4 /* RunLoopCardUpdateAggregatorTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5219194C297B3974007DD5F4 /* RunLoopCardUpdateAggregatorTests.swift */; };
+		52907F662A71199B00518F50 /* DivLastVisibleBoundsCacheTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 52907F652A71199B00518F50 /* DivLastVisibleBoundsCacheTests.swift */; };
+		52CD80672A7122AA00B828B0 /* DivBaseExtensionsTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 52CD80662A7122AA00B828B0 /* DivBaseExtensionsTests.swift */; };
+		52CD80692A7159C200B828B0 /* DivStateExtensionsTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 52CD80682A7159C200B828B0 /* DivStateExtensionsTests.swift */; };
+		52CD806B2A7172B400B828B0 /* XCTestCase+ViewVisibilityCallCount.swift in Sources */ = {isa = PBXBuildFile; fileRef = 52CD806A2A7172B400B828B0 /* XCTestCase+ViewVisibilityCallCount.swift */; };
 		52DED04F29F7349000D64519 /* DivKit in Frameworks */ = {isa = PBXBuildFile; productRef = 52DED04E29F7349000D64519 /* DivKit */; };
 		52DED05129F7349000D64519 /* DivKitExtensions in Frameworks */ = {isa = PBXBuildFile; productRef = 52DED05029F7349000D64519 /* DivKitExtensions */; };
 		52DED05329F734B900D64519 /* ShimmerStyleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 52DED03C29F6E3D500D64519 /* ShimmerStyleTests.swift */; };
@@ -260,6 +264,10 @@
 		437B19D329C8A73300A4C467 /* MaskValidatorTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MaskValidatorTests.swift; sourceTree = "<group>"; };
 		4391F7C22A77DB9B006D8818 /* DivViewController+SwiftUI.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "DivViewController+SwiftUI.swift"; sourceTree = "<group>"; };
 		5219194C297B3974007DD5F4 /* RunLoopCardUpdateAggregatorTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RunLoopCardUpdateAggregatorTests.swift; sourceTree = "<group>"; };
+		52907F652A71199B00518F50 /* DivLastVisibleBoundsCacheTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DivLastVisibleBoundsCacheTests.swift; sourceTree = "<group>"; };
+		52CD80662A7122AA00B828B0 /* DivBaseExtensionsTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DivBaseExtensionsTests.swift; sourceTree = "<group>"; };
+		52CD80682A7159C200B828B0 /* DivStateExtensionsTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DivStateExtensionsTests.swift; sourceTree = "<group>"; };
+		52CD806A2A7172B400B828B0 /* XCTestCase+ViewVisibilityCallCount.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "XCTestCase+ViewVisibilityCallCount.swift"; sourceTree = "<group>"; };
 		52DED03C29F6E3D500D64519 /* ShimmerStyleTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ShimmerStyleTests.swift; sourceTree = "<group>"; };
 		52DED04729F7346900D64519 /* DivKitExtensionsTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = DivKitExtensionsTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		52EEC66D293E64C90030FB11 /* DivBlockModelingContextErrorsTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DivBlockModelingContextErrorsTests.swift; sourceTree = "<group>"; };
@@ -843,6 +851,7 @@
 				8CB960E528883B8E00D16E47 /* Platform.swift */,
 				5219194C297B3974007DD5F4 /* RunLoopCardUpdateAggregatorTests.swift */,
 				8C4DC3E72892946F000C0963 /* RuntimeTestCase.swift */,
+				52907F652A71199B00518F50 /* DivLastVisibleBoundsCacheTests.swift */,
 			);
 			path = DivKitTests;
 			sourceTree = "<group>";
@@ -872,6 +881,9 @@
 				8C7B1B252865C01C0036EF4C /* DivTabsExtensionsTests.swift */,
 				8C7B1B282865C01C0036EF4C /* DivTextExtensionsTests.swift */,
 				8C1CF625286B561F0016D0A1 /* Expected.swift */,
+				52CD80662A7122AA00B828B0 /* DivBaseExtensionsTests.swift */,
+				52CD80682A7159C200B828B0 /* DivStateExtensionsTests.swift */,
+				52CD806A2A7172B400B828B0 /* XCTestCase+ViewVisibilityCallCount.swift */,
 			);
 			path = Extensions;
 			sourceTree = "<group>";
@@ -1505,6 +1517,7 @@
 				8C23F41529DDB3810069F3F7 /* EntityWithArrayOfEnumsTemplate.swift in Sources */,
 				8C23F43229DDB3810069F3F7 /* EntityWithStringArrayPropertyTemplate.swift in Sources */,
 				8C23F44829DDB3810069F3F7 /* StringEnumPropertyTests.swift in Sources */,
+				52CD806B2A7172B400B828B0 /* XCTestCase+ViewVisibilityCallCount.swift in Sources */,
 				8C23F43329DDB3810069F3F7 /* EntityWithStringEnumProperty.swift in Sources */,
 				8C23F44729DDB3810069F3F7 /* StrictArrayTests.swift in Sources */,
 				8C23F43B29DDB3810069F3F7 /* ArrayTests.swift in Sources */,
@@ -1513,6 +1526,7 @@
 				8C1CF626286B561F0016D0A1 /* Expected.swift in Sources */,
 				7035529E28D4881300E237CF /* DivDeserializationErrorsTests.swift in Sources */,
 				E945FC46293E1CA80066C3EA /* Utils.swift in Sources */,
+				52907F662A71199B00518F50 /* DivLastVisibleBoundsCacheTests.swift in Sources */,
 				8C23F41729DDB3810069F3F7 /* EntityWithArrayOfExpressionsTemplate.swift in Sources */,
 				8C23F41D29DDB3810069F3F7 /* EntityWithComplexProperty.swift in Sources */,
 				8C7B1CA62865C01D0036EF4C /* TemplatesTests.swift in Sources */,
@@ -1529,6 +1543,7 @@
 				8C7B1BF32865C01C0036EF4C /* DivTabsExtensionsTests.swift in Sources */,
 				8C23F44429DDB3810069F3F7 /* OptionalStringEnumPropertyTests.swift in Sources */,
 				891672372A5F6F9300121131 /* DivPersistentValuesStorageTests.swift in Sources */,
+				52CD80672A7122AA00B828B0 /* DivBaseExtensionsTests.swift in Sources */,
 				8C23F43F29DDB3810069F3F7 /* EntityProtocol.swift in Sources */,
 				52EEC66E293E64C90030FB11 /* DivBlockModelingContextErrorsTests.swift in Sources */,
 				8C23F42729DDB3810069F3F7 /* EntityWithOptionalStringEnumProperty.swift in Sources */,
@@ -1559,6 +1574,7 @@
 				8C4DC3E82892946F000C0963 /* RuntimeTestCase.swift in Sources */,
 				8C23F42D29DDB3810069F3F7 /* EntityWithSimpleProperties.swift in Sources */,
 				8C23F42B29DDB3810069F3F7 /* EntityWithRequiredProperty.swift in Sources */,
+				52CD80692A7159C200B828B0 /* DivStateExtensionsTests.swift in Sources */,
 				8C23F44329DDB3810069F3F7 /* OptionalPropertyTests.swift in Sources */,
 				8C1DEBCE2A2F8277009237F1 /* DivStateManagementTests.swift in Sources */,
 				8C7B1BFA2865C01C0036EF4C /* DivDataExtensionsTests.swift in Sources */,

client/ios/DivKit/DivBlockModelingContext.swift

@@ -20,6 +20,7 @@ public struct DivBlockModelingContext {
   public var stateManager: DivStateManager
   public let blockStateStorage: DivBlockStateStorage
   public let visibilityCounter: DivVisibilityCounting
+  public let lastVisibleBoundsCache: DivLastVisibleBoundsCache
   public let imageHolderFactory: ImageHolderFactory
   public let highPriorityImageHolderFactory: ImageHolderFactory?
   public let divCustomBlockFactory: DivCustomBlockFactory
@@ -30,6 +31,7 @@ public struct DivBlockModelingContext {
   private let variables: DivVariables
   public let layoutDirection: UserInterfaceLayoutDirection
   public let debugParams: DebugParams
+  public let scheduler: Scheduling
   public let playerFactory: PlayerFactory?
   public var childrenA11yDescription: String?
   public weak var parentScrollView: ScrollView?
@@ -61,6 +63,7 @@ public struct DivBlockModelingContext {
     stateManager: DivStateManager,
     blockStateStorage: DivBlockStateStorage = DivBlockStateStorage(),
     visibilityCounter: DivVisibilityCounting = DivVisibilityCounter(),
+    lastVisibleBoundsCache: DivLastVisibleBoundsCache = DivLastVisibleBoundsCache(),
     imageHolderFactory: ImageHolderFactory,
     highPriorityImageHolderFactory: ImageHolderFactory? = nil,
     divCustomBlockFactory: DivCustomBlockFactory = EmptyDivCustomBlockFactory(),
@@ -71,6 +74,7 @@ public struct DivBlockModelingContext {
     variables: DivVariables = [:],
     playerFactory: PlayerFactory? = nil,
     debugParams: DebugParams = DebugParams(),
+    scheduler: Scheduling? = nil,
     childrenA11yDescription: String? = nil,
     parentScrollView: ScrollView? = nil,
     errorsStorage: DivErrorsStorage = DivErrorsStorage(errors: []),
@@ -85,6 +89,7 @@ public struct DivBlockModelingContext {
     self.stateManager = stateManager
     self.blockStateStorage = blockStateStorage
     self.visibilityCounter = visibilityCounter
+    self.lastVisibleBoundsCache = lastVisibleBoundsCache
     self.imageHolderFactory = imageHolderFactory
     self.highPriorityImageHolderFactory = highPriorityImageHolderFactory
     self.divCustomBlockFactory = divCustomBlockFactory
@@ -93,6 +98,7 @@ public struct DivBlockModelingContext {
     self.variables = variables
     self.playerFactory = playerFactory
     self.debugParams = debugParams
+    self.scheduler = scheduler ?? TimerScheduler()
     self.childrenA11yDescription = childrenA11yDescription
     self.parentScrollView = parentScrollView
     self.errorsStorage = errorsStorage

client/ios/DivKit/DivKitComponents.swift

@@ -33,6 +33,7 @@ public final class DivKitComponents {
   public let urlHandler: DivUrlHandler
   public let variablesStorage: DivVariablesStorage
   public let visibilityCounter = DivVisibilityCounter()
+  public let lastVisibleBoundsCache = DivLastVisibleBoundsCache()
   public var updateCardSignal: Signal<[DivActionURLHandler.UpdateReason]> {
     updateCardPipe.signal
   }
@@ -227,6 +228,7 @@ public final class DivKitComponents {
       stateManager: stateManagement.getStateManagerForCard(cardId: cardId),
       blockStateStorage: blockStateStorage,
       visibilityCounter: visibilityCounter,
+      lastVisibleBoundsCache: lastVisibleBoundsCache,
       imageHolderFactory: imageHolderFactory
         .withInMemoryCache(cachedImageHolders: cachedImageHolders),
       divCustomBlockFactory: divCustomBlockFactory,

client/ios/DivKit/DivLastVisibleBoundsCache.swift

@@ -0,0 +1,40 @@
+import CoreGraphics
+import LayoutKit
+import CommonCorePublic
+
+public final class DivLastVisibleBoundsCache {
+  private let rwLock = RWLock()
+
+  private var storage: [UIElementPath: CGRect] = [:]
+
+  public init() {}
+
+  public func lastVisibleBounds(for path: UIElementPath) -> CGRect {
+    rwLock.read {
+      storage[path] ?? .zero
+    }
+  }
+
+  public func updateLastVisibleBounds(for path: UIElementPath, bounds: CGRect) {
+    rwLock.write {
+      storage[path] = bounds
+    }
+  }
+
+  public func dropVisibleBounds(forMatchingPrefix prefix: UIElementPath) {
+    let prefix = prefix.description + "/"
+    rwLock.write {
+      storage.forEach {
+        if ($0.key.description + "/").starts(with: prefix) {
+          storage[$0.key] = nil
+        }
+      }
+    }
+  }
+
+  public func reset() {
+    rwLock.write {
+      storage.removeAll()
+    }
+  }
+}

client/ios/DivKit/Extensions/DivBase/DivBaseExtensions.swift

@@ -21,6 +21,7 @@ extension DivBase {
 
     let visibility = resolveVisibility(expressionResolver)
     if visibility == .gone {
+      context.lastVisibleBoundsCache.dropVisibleBounds(forMatchingPrefix: context.parentPath)
       context.stateManager.setBlockVisibility(statePath: statePath, div: self, isVisible: false)
       return EmptyBlock.zeroSized
     }
@@ -39,6 +40,7 @@ extension DivBase {
 
     let externalInsets = margins.makeEdgeInsets(context: context)
     if visibility == .invisible {
+      context.lastVisibleBoundsCache.dropVisibleBounds(forMatchingPrefix: context.parentPath)
       context.stateManager.setBlockVisibility(statePath: statePath, div: self, isVisible: false)
       block = applyExtensionHandlersAfterBaseProperties(
         to: block.addingEdgeInsets(externalInsets),
@@ -72,6 +74,16 @@ extension DivBase {
       border: border.makeBlockBorder(with: expressionResolver),
       shadow: border.makeBlockShadow(with: expressionResolver),
       visibilityActions: visibilityActions.isEmpty ? nil : visibilityActions,
+      lastVisibleBounds: visibilityActions.isEmpty ? nil : Property<CGRect>(
+        getter: { context.lastVisibleBoundsCache.lastVisibleBounds(for: context.parentPath) },
+        setter: {
+          context.lastVisibleBoundsCache.updateLastVisibleBounds(
+            for: context.parentPath,
+            bounds: $0
+          )
+        }
+      ),
+      scheduler: context.scheduler,
       tooltips: try makeTooltips(context: context)
     )
     .addingTransform(

client/ios/DivKit/Extensions/DivData/DivDataExtensions.swift

@@ -11,6 +11,10 @@ extension DivData: DivBlockModeling {
       throw DivBlockModelingError("DivData has no states", path: context.parentPath)
     }
 
+    if let previousRootState = getPreviousRootState(stateManager: stateManager) {
+      context.lastVisibleBoundsCache.dropVisibleBounds(forMatchingPrefix: context.parentPath + previousRootState.rawValue)
+    }
+
     let stateId = String(state.stateId)
     let statePath = DivStatePath(rawValue: UIElementPath(stateId))
     let div = state.div
@@ -31,7 +35,6 @@ extension DivData: DivBlockModeling {
     )
     return block
       .addingStateBlock(
-        stateId: stateId,
         ids: stateManager.getVisibleIds(statePath: statePath)
       )
       .addingDebugInfo(context: divContext)
@@ -53,6 +56,22 @@ extension DivData: DivBlockModeling {
     context.addError(level: .error, message: "DivData.State not found: \(stateId)")
     return states.first
   }
+
+  private func getPreviousRootState(stateManager: DivStateManager) -> DivStateID? {
+    guard let item = stateManager.get(stateBlockPath: DivData.rootPath) else {
+      return nil
+    }
+
+    switch item.previousState {
+    case .empty, .initial:
+      return nil
+    case let .withID(id):
+      if item.currentStateID != id {
+        return id
+      }
+      return nil
+    }
+  }
 }
 
 extension DivData {

client/ios/DivKit/Extensions/DivStateExtensions.swift

@@ -46,6 +46,8 @@ extension DivState: DivBlockModeling {
        let previousState = getPreviousState(stateManagerItem: stateManagerItem),
        previousState.stateId != activeStateId,
        let previousDiv = previousState.div {
+      // state changed -> drop visibility cache for all children
+      context.lastVisibleBoundsCache.dropVisibleBounds(forMatchingPrefix: context.parentPath)
       previousBlock = try previousDiv.value.makeBlock(
         context: context.makeContextForState(
           id: id,
@@ -99,7 +101,6 @@ extension DivState: DivBlockModeling {
         ),
       ]
     ).addingStateBlock(
-      stateId: activeStateId,
       ids: stateManager.getVisibleIds(statePath: activeStatePath)
     )
   }

client/ios/DivKitTests/DivKitTests.swift

@@ -1,7 +1,7 @@
 import XCTest
 
-@testable import DivKit
 import CommonCorePublic
+@testable import DivKit
 import LayoutKit
 import NetworkingPublic
 import Serialization
@@ -48,7 +48,8 @@ extension DivBlockModelingContext {
   static let `default` = DivBlockModelingContext()
 
   init(
-    blockStateStorage: DivBlockStateStorage = DivBlockStateStorage()
+    blockStateStorage: DivBlockStateStorage = DivBlockStateStorage(),
+    scheduler: Scheduling? = nil
   ) {
     self.init(
       cardId: DivKitTests.cardId,
@@ -56,6 +57,7 @@ extension DivBlockModelingContext {
       stateManager: DivStateManager(),
       blockStateStorage: blockStateStorage,
       imageHolderFactory: ImageHolderFactory(make: { _, _ in FakeImageHolder() }),
+      scheduler: scheduler,
       persistentValuesStorage: DivPersistentValuesStorage()
     )
   }

client/ios/DivKitTests/DivLastVisibleBoundsCacheTests.swift

@@ -0,0 +1,50 @@
+import DivKit
+import LayoutKit
+import XCTest
+
+final class DivLastVisibleBoundsCacheTests: XCTestCase {
+  let cache = DivLastVisibleBoundsCache()
+    
+  func test_WhenCacheIsEmpty_RetrievesZeroFromCache() {
+    XCTAssertEqual(cache.lastVisibleBounds(for: "path"), .zero)
+  }
+
+  func test_WhenUpdateLastVisibleBounds_RetrievesUpdatedValueFromCache() {
+    let rect = CGRect(origin: CGPoint(x: 10, y: 10), size: CGSize(squareDimension: 10))
+
+    cache.updateLastVisibleBounds(for: "path", bounds: rect)
+
+    XCTAssertEqual(cache.lastVisibleBounds(for: "path"), rect)
+  }
+
+  func test_WhenReset_RetrievesZeroFromCache() {
+    let rect = CGRect(origin: CGPoint(x: 10, y: 10), size: CGSize(squareDimension: 10))
+
+    cache.updateLastVisibleBounds(for: "path", bounds: rect)
+    cache.reset()
+
+    XCTAssertEqual(cache.lastVisibleBounds(for: "path"), .zero)
+  }
+
+  func test_WhenDropVisibleBoundsWithMatchingPrefix_ClearsAllChildPaths() {
+    let rect1 = CGRect(origin: CGPoint(x: 10, y: 10), size: CGSize(squareDimension: 10))
+    let rect2 = CGRect(origin: .zero, size: CGSize(squareDimension: 10))
+    let rect3 = CGRect(origin: .zero, size: CGSize(squareDimension: 20))
+    let parentPath: UIElementPath = "path"
+    let parentPath2: UIElementPath = "path2"
+    let childPath: UIElementPath = parentPath + "child"
+    let nestedChildPath: UIElementPath = childPath + "nestedChild"
+
+    cache.updateLastVisibleBounds(for: parentPath, bounds: rect1)
+    cache.updateLastVisibleBounds(for: parentPath2, bounds: rect1)
+    cache.updateLastVisibleBounds(for: childPath, bounds: rect2)
+    cache.updateLastVisibleBounds(for: nestedChildPath, bounds: rect3)
+
+    cache.dropVisibleBounds(forMatchingPrefix: parentPath)
+
+    XCTAssertEqual(cache.lastVisibleBounds(for: childPath), .zero)
+    XCTAssertEqual(cache.lastVisibleBounds(for: nestedChildPath), .zero)
+    XCTAssertEqual(cache.lastVisibleBounds(for: parentPath2), rect1)
+    XCTAssertEqual(cache.lastVisibleBounds(for: parentPath), .zero)
+  }
+}

client/ios/DivKitTests/Extensions/DivBaseExtensionsTests.swift

@@ -0,0 +1,86 @@
+@testable import LayoutKit
+
+import XCTest
+
+import CommonCorePublic
+import DivKit
+import NetworkingPublic
+
+final class DivBaseExtensionsTests: XCTestCase {
+  private let timer = TestTimerScheduler()
+
+  func test_WhenCreatesBlockAfterItBeingGone_ReportsVisibility() throws {
+    try expectVisibilityActionsToRun(
+      forVisibleBlockFile: "div-text-visibility-actions-visible",
+      invisibleBlockFile: "div-text-visibility-actions-gone"
+    )
+  }
+
+  func test_WhenCreatesBlockAfterItBeingInvisible_ReportsVisibility() throws {
+    try expectVisibilityActionsToRun(
+      forVisibleBlockFile: "div-text-visibility-actions-visible",
+      invisibleBlockFile: "div-text-visibility-actions-invisible"
+    )
+  }
+
+  func test_WhenReusesBlockWithAnotherDivCardID_ExpectToCancelPreviousBlockTimers() throws {
+    let context = DivBlockModelingContext(scheduler: timer)
+
+    let firstBlock = try makeBlock(fromFile: "div-text-visibility-actions-visible", context: context)
+
+    // trigger visibility actions for first time
+    let rect = CGRect(origin: .zero, size: CGSize(squareDimension: 20))
+    let view = firstBlock.makeBlockView()
+    view.frame = rect
+    view.layoutIfNeeded()
+    view.onVisibleBoundsChanged(from: rect, to: rect)
+
+    let oldTimers = timer.timers
+
+    let secondBlock = try makeBlock(
+      fromFile: "div-text-visibility-actions-visible",
+      context: DivBlockModelingContext(
+        cardId: "another_cardId",
+        stateManager: DivStateManager(),
+        imageHolderFactory: ImageHolderFactory(make: { _, _ in FakeImageHolder() })
+      )
+    )
+    let view2 = secondBlock.reuse(view, observer: nil, overscrollDelegate: nil, renderingDelegate: nil, superview: nil)
+    view2.frame = rect
+    view2.layoutIfNeeded()
+    view.onVisibleBoundsChanged(from: rect, to: rect)
+
+    XCTAssertEqual(oldTimers.allSatisfy { !$0.isValid }, true)
+  }
+
+  private func expectVisibilityActionsToRun(
+    forVisibleBlockFile file: String,
+    invisibleBlockFile: String
+  ) throws {
+    let context = DivBlockModelingContext(scheduler: timer)
+    
+    let blockVisibleFirst = try makeBlock(fromFile: file, context: context)
+
+    // trigger visibility actions for first time
+    let rect = CGRect(origin: .zero, size: CGSize(squareDimension: 20))
+    let view = blockVisibleFirst.makeBlockView()
+    XCTAssertEqual(getViewVisibilityCallCount(view: view, rect: rect, timerScheduler: timer), 1)
+
+    // expect to drop lastVisibleBounds
+    let _ = try makeBlock(fromFile: invisibleBlockFile, context: context)
+    let view2 = blockVisibleFirst.makeBlockView()
+
+    XCTAssertEqual(getViewVisibilityCallCount(view: view2, rect: rect, timerScheduler: timer), 1)
+  }
+}
+
+private func makeBlock(
+  fromFile filename: String,
+  context: DivBlockModelingContext = .default
+) throws -> Block {
+  try DivTextTemplate.make(
+    fromFile: filename,
+    subdirectory: "div-base",
+    context: context
+  )
+}

client/ios/DivKitTests/Extensions/DivDataExtensionsTests.swift

@@ -60,6 +60,26 @@ final class DivDataExtensionsTests: XCTestCase {
     let expectedPath = UIElementPath.root + "0" + DivGallery.type
     XCTAssertEqual(galleryBlock?.model.path, expectedPath)
   }
+
+  func test_WhenStateChanges_ReportsVisibilityForNewState() throws {
+    let timerScheduler = TestTimerScheduler()
+    let context = DivBlockModelingContext(scheduler: timerScheduler)
+
+    for rootStateId in [nil, "1", "0", "1"] {
+      if let rootStateId {
+        context.stateManager.setStateWithHistory(path: DivData.rootPath, stateID: DivStateID(rawValue: rootStateId))
+      }
+
+      let block = try makeBlock(fromFile: "root_states_visibility", context: context)
+
+      let rect = CGRect(
+        origin: .zero,
+        size: CGSize(width: 100, height: block.intrinsicContentHeight(forWidth: 100))
+      )
+      let view = block.makeBlockView()
+      XCTAssertEqual(getViewVisibilityCallCount(view: view, rect: rect, timerScheduler: timerScheduler), 1)
+    }
+  }
 }
 
 private let data = makeDivData(
@@ -103,3 +123,15 @@ extension Block {
     return self
   }
 }
+
+private func makeBlock(
+  fromFile filename: String,
+  context: DivBlockModelingContext = .default
+) throws -> Block {
+  try DivDataTemplate.make(
+    fromFile: filename,
+    subdirectory: "div-data",
+    context: context
+  )
+}
+

client/ios/DivKitTests/Extensions/DivStateExtensionsTests.swift

@@ -0,0 +1,66 @@
+@testable import LayoutKit
+
+import XCTest
+
+import CommonCorePublic
+import DivKit
+
+final class DivStateExtensionsTests: XCTestCase {
+  private let timerScheduler = TestTimerScheduler()
+  func test_WhenVisibilityWasTriggeredAndStateChanges_ReportsVisibilityAgain() throws {
+    let context = DivBlockModelingContext(scheduler: timerScheduler)
+
+    let block = try makeBlock(fromFile: "states_visibility", context: context)
+    let rect = CGRect(
+      origin: .zero,
+      size: CGSize(width: 100, height: block.intrinsicContentHeight(forWidth: 100))
+    )
+    let view = block.makeBlockView()
+    XCTAssertEqual(getViewVisibilityCallCount(view: view, rect: rect, timerScheduler: timerScheduler), 1)
+
+    context.stateManager.setState(stateBlockPath: "mystate", stateID: "second")
+
+    let block2 = try makeBlock(fromFile: "states_visibility", context: context)
+    let view2 = block2.reuse(
+      view,
+      observer: nil,
+      overscrollDelegate: nil,
+      renderingDelegate: nil,
+      superview: nil
+    )
+    XCTAssertEqual(getViewVisibilityCallCount(view: view2, rect: rect, timerScheduler: timerScheduler), 1)
+  }
+
+  func test_WhenVisibilityWasTriggeredAndStateDoesNotChange_DoesNotReportVisibilityAgain() throws {
+    let context = DivBlockModelingContext(scheduler: timerScheduler)
+
+    let block = try makeBlock(fromFile: "states_visibility", context: context)
+    let rect = CGRect(
+      origin: .zero,
+      size: CGSize(width: 100, height: block.intrinsicContentHeight(forWidth: 100))
+    )
+    let view = block.makeBlockView()
+    XCTAssertEqual(getViewVisibilityCallCount(view: view, rect: rect, timerScheduler: timerScheduler), 1)
+
+    let block2 = try makeBlock(fromFile: "states_visibility", context: context)
+    let view2 = block2.reuse(
+      view,
+      observer: nil,
+      overscrollDelegate: nil,
+      renderingDelegate: nil,
+      superview: nil
+    )
+    XCTAssertEqual(getViewVisibilityCallCount(view: view2, rect: rect, timerScheduler: timerScheduler), 0)
+  }
+}
+
+private func makeBlock(
+  fromFile filename: String,
+  context: DivBlockModelingContext = .default
+) throws -> Block {
+  try DivStateTemplate.make(
+    fromFile: filename,
+    subdirectory: "div-state",
+    context: context
+  )
+}

client/ios/DivKitTests/Extensions/XCTestCase+ViewVisibilityCallCount.swift

@@ -0,0 +1,28 @@
+import LayoutKit
+import XCTest
+
+extension XCTestCase {
+  func getViewVisibilityCallCount(
+    view: BlockView,
+    rect: CGRect,
+    timerScheduler: TestTimerScheduler
+  ) -> Int {
+    let performer = UIActionEventPerformerMock()
+
+    performer.addSubview(view)
+    view.frame = rect
+    view.layoutIfNeeded()
+    view.onVisibleBoundsChanged(from: rect, to: rect)
+    timerScheduler.timers.forEach { guard $0.isValid else { return }; $0.fire() }
+
+    return performer.callCount
+  }
+}
+
+private class UIActionEventPerformerMock: UIView, UIActionEventPerforming {
+  var callCount: Int = 0
+
+  func perform(uiActionEvent _: UIActionEvent, from _: AnyObject) {
+    callCount += 1
+  }
+}

client/ios/LayoutKit/LayoutKit/Blocks/Decorations/Block+Decorations.swift

@@ -27,6 +27,8 @@ extension Block {
     longTapActions: LongTapActions? = nil,
     analyticsURL: URL? = nil,
     visibilityActions: [VisibilityAction]? = nil,
+    scheduler: Scheduling? = nil,
+    lastVisibleBounds: Property<CGRect>? = nil,
     tooltips: [BlockTooltip]? = nil,
     forceWrapping: Bool,
     accessibilityElement: AccessibilityElement? = nil
@@ -92,6 +94,8 @@ extension Block {
         childAlpha: alpha.map { $0 * block.childAlpha },
         blurEffect: blurEffect ?? block.blurEffect,
         visibilityActions: visibilityActions ?? block.visibilityActions,
+        scheduler: scheduler ?? block.scheduler,
+        lastVisibleBounds: lastVisibleBounds ?? block.lastVisibleBounds,
         tooltips: [tooltips, block.tooltips].compactMap { $0 }.flatMap { $0 },
         accessibilityElement: accessibilityElement
       )
@@ -116,6 +120,8 @@ extension Block {
       childAlpha: alpha ?? DecoratingBlock.defaultChildAlpha,
       blurEffect: blurEffect,
       visibilityActions: visibilityActions ?? [],
+      scheduler: scheduler,
+      lastVisibleBounds: lastVisibleBounds,
       tooltips: tooltips ?? [],
       accessibilityElement: accessibilityElement
     )
@@ -143,6 +149,8 @@ extension Block {
     analyticsURL: URL? = nil,
     shadow: BlockShadow? = nil,
     visibilityActions: [VisibilityAction]? = nil,
+    lastVisibleBounds: Property<CGRect>? = nil,
+    scheduler: Scheduling? = nil,
     tooltips: [BlockTooltip]? = nil,
     forceWrapping: Bool = false,
     accessibilityElement: AccessibilityElement? = nil
@@ -160,6 +168,8 @@ extension Block {
       longTapActions: longTapActions,
       analyticsURL: analyticsURL,
       visibilityActions: visibilityActions,
+      scheduler: scheduler,
+      lastVisibleBounds: lastVisibleBounds,
       tooltips: tooltips,
       forceWrapping: forceWrapping,
       accessibilityElement: accessibilityElement

client/ios/LayoutKit/LayoutKit/Blocks/Decorations/DecoratingBlock.swift

@@ -25,6 +25,8 @@ final class DecoratingBlock: WrapperBlock {
   let blurEffect: BlurEffect?
   let paddings: EdgeInsets
   let visibilityActions: [VisibilityAction]
+  let scheduler: Scheduling?
+  let lastVisibleBounds: Property<CGRect>?
   let tooltips: [BlockTooltip]
   let accessibilityElement: AccessibilityElement?
 
@@ -43,6 +45,8 @@ final class DecoratingBlock: WrapperBlock {
     blurEffect: BlurEffect? = nil,
     paddings: EdgeInsets = .zero,
     visibilityActions: [VisibilityAction] = [],
+    scheduler: Scheduling? = nil,
+    lastVisibleBounds: Property<CGRect>? = nil,
     tooltips: [BlockTooltip] = [],
     accessibilityElement: AccessibilityElement? = nil
   ) {
@@ -60,6 +64,8 @@ final class DecoratingBlock: WrapperBlock {
     self.blurEffect = blurEffect
     self.paddings = paddings
     self.visibilityActions = visibilityActions
+    self.scheduler = scheduler
+    self.lastVisibleBounds = lastVisibleBounds
     self.tooltips = tooltips
     self.accessibilityElement = accessibilityElement
   }
@@ -144,6 +150,8 @@ extension DecoratingBlock {
     blurEffect: BlurEffect? = nil,
     paddings: EdgeInsets? = nil,
     visibilityActions: [VisibilityAction]? = nil,
+    scheduler: Scheduling? = nil,
+    lastVisibleBounds: Property<CGRect>? = nil,
     tooltips: [BlockTooltip]? = nil,
     accessibilityElement: AccessibilityElement? = nil
   ) -> DecoratingBlock {
@@ -162,6 +170,8 @@ extension DecoratingBlock {
       blurEffect: blurEffect ?? self.blurEffect,
       paddings: paddings ?? self.paddings,
       visibilityActions: visibilityActions ?? self.visibilityActions,
+      scheduler: scheduler ?? self.scheduler,
+      lastVisibleBounds: lastVisibleBounds ?? self.lastVisibleBounds,
       tooltips: tooltips ?? self.tooltips,
       accessibilityElement: accessibilityElement ?? self.accessibilityElement
     )

client/ios/LayoutKit/LayoutKit/Blocks/StateBlock.swift

@@ -2,16 +2,13 @@ import CommonCorePublic
 
 public final class StateBlock: WrapperBlock, LayoutCachingDefaultImpl {
   public let child: Block
-  public let stateId: String
   public let ids: Set<String>
 
   public init(
     child: Block,
-    stateId: String,
     ids: Set<String>
   ) {
     self.child = child
-    self.stateId = stateId
     self.ids = ids
   }
 
@@ -23,14 +20,13 @@ public final class StateBlock: WrapperBlock, LayoutCachingDefaultImpl {
   }
 
   public func makeCopy(wrapping child: Block) -> StateBlock {
-    StateBlock(child: child, stateId: stateId, ids: ids)
+    StateBlock(child: child, ids: ids)
   }
 }
 
 extension StateBlock: Equatable {
   public static func ==(lhs: StateBlock, rhs: StateBlock) -> Bool {
     lhs.child == rhs.child
-      && lhs.stateId == rhs.stateId
       && lhs.ids == rhs.ids
   }
 }
@@ -41,9 +37,8 @@ extension StateBlock: CustomDebugStringConvertible {
 
 extension Block {
   public func addingStateBlock(
-    stateId: String,
     ids: Set<String>
   ) -> Block {
-    StateBlock(child: self, stateId: stateId, ids: ids)
+    StateBlock(child: self, ids: ids)
   }
 }

client/ios/LayoutKit/LayoutKit/UI/Blocks/DecoratingBlock+UIViewRenderableBlock.swift

@@ -38,7 +38,9 @@ extension DecoratingBlock {
       blurEffect: blurEffect,
       paddings: paddings,
       source: Variable { [weak self] in self },
+      scheduler: scheduler,
       visibilityActions: visibilityActions,
+      lastVisibleBounds: lastVisibleBounds,
       tooltips: tooltips,
       accessibility: accessibilityElement
     )
@@ -101,7 +103,9 @@ private final class DecoratingView: UIControl, BlockViewProtocol, VisibleBoundsT
     let blurEffect: BlurEffect?
     let paddings: EdgeInsets
     let source: Variable<AnyObject?>
+    let scheduler: Scheduling?
     let visibilityActions: [VisibilityAction]
+    let lastVisibleBounds: Property<CGRect>?
     let tooltips: [BlockTooltip]
     let accessibility: AccessibilityElement?
 
@@ -289,6 +293,7 @@ private final class DecoratingView: UIControl, BlockViewProtocol, VisibleBoundsT
     guard model != self.model || observer !== self.observer else {
       return
     }
+    let oldModel = self.model
 
     if self.model?.tooltips.isEmpty ?? true, !model.tooltips.isEmpty {
       renderingDelegate?.tooltipAnchorViewAdded(anchorView: self)
@@ -320,24 +325,28 @@ private final class DecoratingView: UIControl, BlockViewProtocol, VisibleBoundsT
     model.actions?
       .forEach { applyAccessibility($0.accessibilityElement) }
 
-    visibilityActionPerformers = model.visibilityActions.isEmpty
-      ? nil
-      : VisibilityActionPerformers(
-        visibilityCheckParams: model.visibilityActions.map { visibilityAction in
-          VisibilityCheckParam(
-            requiredDuration: visibilityAction.requiredDuration,
-            targetPercentage: visibilityAction.targetPercentage,
-            limiter: visibilityAction.limiter,
-            action: { [unowned self] in
-              UIActionEvent(
-                uiAction: visibilityAction.uiAction,
-                originalSender: self
-              ).sendFrom(self)
-            },
-            type: visibilityAction.actionType
-          )
-        }
-      )
+    if oldModel?.visibilityActions != model.visibilityActions {
+      visibilityActionPerformers = model.visibilityActions.isEmpty
+        ? nil
+        : VisibilityActionPerformers(
+          visibilityCheckParams: model.visibilityActions.map { visibilityAction in
+            VisibilityCheckParam(
+              requiredDuration: visibilityAction.requiredDuration,
+              targetPercentage: visibilityAction.targetPercentage,
+              limiter: visibilityAction.limiter,
+              action: { [unowned self] in
+                UIActionEvent(
+                  uiAction: visibilityAction.uiAction,
+                  originalSender: self
+                ).sendFrom(self)
+              },
+              type: visibilityAction.actionType
+            )
+          },
+          lastVisibleBounds: model.lastVisibleBounds ?? Property(initialValue: .zero),
+          scheduling: model.scheduler ?? TimerScheduler()
+        )
+    }
 
     tapRecognizer.isEnabled = model.shouldHandleTap
     doubleTapRecognizer.isEnabled = model.shouldHandleDoubleTap

client/ios/LayoutKit/LayoutKit/UI/Blocks/StateBlock+UIViewRenderableBlock.swift

@@ -19,7 +19,6 @@ extension StateBlock {
   ) {
     (view as! StateBlockView).configure(
       child: child,
-      stateId: stateId,
       ids: Set(ids.map { BlockViewID(rawValue: $0) }),
       observer: observer,
       overscrollDelegate: overscrollDelegate,
@@ -109,7 +108,6 @@ private final class StateBlockView: BlockView {
   private var subviewStorage = SubviewStorage(wrappedRenderingDelegate: nil, ids: [])
   private var childView: BlockView?
   private var stateId: String?
-  private var isStateChanged = false
 
   var effectiveBackgroundColor: UIColor? { childView?.effectiveBackgroundColor }
 
@@ -124,17 +122,11 @@ private final class StateBlockView: BlockView {
 
   func configure(
     child: Block,
-    stateId: String,
     ids: Set<BlockViewID>,
     observer: ElementStateObserver?,
     overscrollDelegate: ScrollDelegate?,
     renderingDelegate: RenderingDelegate?
   ) {
-    if (self.stateId != stateId) {
-      isStateChanged = true
-      self.stateId = stateId
-    }
-
     // remove views with unfinished animations
     subviews.forEach {
       if $0 !== childView {
@@ -188,15 +180,6 @@ private final class StateBlockView: BlockView {
 }
 
 extension StateBlockView: VisibleBoundsTrackingContainer {
-  func onVisibleBoundsChanged(from: CGRect, to: CGRect) {
-    if isStateChanged {
-      isStateChanged = false
-      passVisibleBoundsChanged(from: .zero, to: to)
-    } else {
-      passVisibleBoundsChanged(from: from, to: to)
-    }
-  }
-
   var visibleBoundsTrackingSubviews: [VisibleBoundsTrackingView] {
     childView.asArray()
   }

client/ios/LayoutKit/LayoutKit/ViewModels/VisibilityActionPerformer/VisibilityActionPerformer.swift

@@ -22,7 +22,7 @@ final class VisibilityActionPerformer {
     limiter: ActionLimiter,
     action: @escaping Action,
     type: VisibilityActionType,
-    timerScheduler: Scheduling = TimerScheduler()
+    timerScheduler: Scheduling
   ) {
     self.requiredDuration = requiredDuration
     self.targetPercentage = targetVisibilityPercentage

client/ios/LayoutKit/LayoutKit/ViewModels/VisibilityActionPerformer/VisibilityActionPerformers.swift

@@ -1,15 +1,29 @@
 import CoreGraphics
 import Foundation
 
+import BasePublic
+
 public final class VisibilityActionPerformers {
   private let actionPerformers: [VisibilityActionPerformer]
+  private let lastVisibleBounds: Property<CGRect>
 
-  init(visibilityCheckParams: [VisibilityCheckParam]) {
-    actionPerformers = visibilityCheckParams.map(VisibilityActionPerformer.init)
+  init(
+    visibilityCheckParams: [VisibilityCheckParam],
+    lastVisibleBounds: Property<CGRect>,
+    scheduling: Scheduling
+  ) {
+    self.lastVisibleBounds = lastVisibleBounds
+    actionPerformers = visibilityCheckParams.map {
+      VisibilityActionPerformer(visibilityCheckParam: $0, scheduling: scheduling)
+    }
   }
 
-  func onVisibleBoundsChanged(from: CGRect, to: CGRect, bounds: CGRect) {
-    let visibleAreaPercentageBefore = bounds.isEmpty ? 0 : Int(from.area * 100 / bounds.area)
+  func onVisibleBoundsChanged(from _: CGRect, to: CGRect, bounds: CGRect) {
+    let beforeVisibleBounds = lastVisibleBounds.value
+    lastVisibleBounds.value = to
+
+    let visibleAreaPercentageBefore = bounds
+      .isEmpty ? 0 : Int(beforeVisibleBounds.area * 100 / bounds.area)
     let visibleAreaPercentageAfter = bounds.isEmpty ? 0 : Int(to.area * 100 / bounds.area)
 
     for performer in actionPerformers {
@@ -22,13 +36,14 @@ public final class VisibilityActionPerformers {
 }
 
 extension VisibilityActionPerformer {
-  fileprivate convenience init(visibilityCheckParam: VisibilityCheckParam) {
+  fileprivate convenience init(visibilityCheckParam: VisibilityCheckParam, scheduling: Scheduling) {
     self.init(
       requiredDuration: visibilityCheckParam.requiredDuration,
       targetVisibilityPercentage: visibilityCheckParam.targetPercentage,
       limiter: visibilityCheckParam.limiter,
       action: visibilityCheckParam.action,
-      type: visibilityCheckParam.type
+      type: visibilityCheckParam.type,
+      timerScheduler: scheduling
     )
   }
 }

test_data/unit_test_data/div-base/div-text-visibility-actions-gone.json

@@ -0,0 +1,11 @@
+{
+  "type": "text",
+  "text": "text",
+  "visibility": "gone",
+  "visibility_actions": [
+    {
+      "log_id": "some",
+      "log_limit": 0
+    }
+  ]
+}

test_data/unit_test_data/div-base/div-text-visibility-actions-invisible.json

@@ -0,0 +1,12 @@
+{
+  "type": "text",
+  "text": "text",
+  "visibility": "invisible",
+  "visibility_actions": [
+    {
+      "log_id": "some",
+      "log_limit": 0
+    }
+  ]
+}
+

test_data/unit_test_data/div-base/div-text-visibility-actions-visible.json

@@ -0,0 +1,12 @@
+{
+  "type": "text",
+  "text": "text",
+  "visibility": "visibile",
+  "visibility_actions": [
+    {
+      "log_id": "some",
+      "log_limit": 0,
+      "visibility_duration": 0
+    }
+  ]
+}

test_data/unit_test_data/div-data/root_states_visibility.json

@@ -0,0 +1,28 @@
+{
+  "log_id": "sample_card",
+  "states": [
+    {
+      "state_id": 0,
+      "div": {
+        "type": "text",
+        "text": "state zero",
+        "visibility_action": {
+          "log_id": "zero state visible",
+          "log_limit": 0
+        }
+      }
+    },
+    {
+      "state_id": 1,
+      "div": {
+        "type": "text",
+        "text": "state first",
+        "visibility_action": {
+          "log_id": "first state visible",
+          "log_limit": 0
+        }
+      }
+    }
+  ]
+}
+

test_data/unit_test_data/div-state/states_visibility.json

@@ -0,0 +1,28 @@
+{
+  "type": "state",
+  "id": "mystate",
+  "states": [
+    {
+      "state_id": "first",
+      "div": {
+        "type": "text",
+        "text": "state first",
+        "visibility_action": {
+          "log_id": "first state visible",
+          "log_limit": 0
+        }
+      }
+    },
+    {
+      "state_id": "second",
+      "div": {
+        "type": "text",
+        "text": "seconds first",
+        "visibility_action": {
+          "log_id": "second state visible",
+          "log_limit": 0
+        }
+      }
+    }
+  ]
+}