Fix iOS 26 swipe-back conflict with horizontal Compose scrollables

compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/window/InputViews.ios.kt

@@ -46,6 +46,7 @@ import platform.CoreGraphics.CGPoint
 import platform.CoreGraphics.CGRectIsEmpty
 import platform.CoreGraphics.CGRectZero
 import platform.Foundation.NSSelectorFromString
+import platform.Foundation.NSStringFromClass
 import platform.UIKit.UIEvent
 import platform.UIKit.UIEventTypeTouches
 import platform.UIKit.UIGestureRecognizer
@@ -66,6 +67,7 @@ import platform.UIKit.UIView
 import platform.UIKit.endEditing
 import platform.UIKit.setAccessibilityElements
 import platform.UIKit.setState
+import platform.darwin.NSObject
 
 /**
  * A reason for why touches are sent to Compose
@@ -295,7 +297,7 @@ private class TouchesGestureRecognizer(
         return if (isInChildHierarchy(preventedGestureRecognizer.view)) {
             super.canPreventGestureRecognizer(preventedGestureRecognizer)
         } else if (preventedGestureRecognizer is UIScreenEdgePanGestureRecognizer) {
-            false
+            preventedGestureRecognizer.isUINavigationControllerContentSwipeGestureRecognizer()
         } else {
             state == UIGestureRecognizerStatePossible || state.isOngoing
         }
@@ -872,3 +874,21 @@ private fun UIView?.hasTrackingUIScrollView(): Boolean {
     }
     return false
 }
+
+/**
+ * Detects the private UIKit recognizer that drives iOS 26 full-width `UINavigationController`
+ * swipe-back interaction. It is a subclass of `UIScreenEdgePanGestureRecognizer` which can start
+ * anywhere across the horizontal axis of the screen.
+ *
+ * Compose needs to be able to prevent this recognizer after Compose content consumes horizontal
+ * movement, for example when a `HorizontalPager` handles the drag. Without that, UIKit can start
+ * the navigation pop transition first and cancel Compose's touch stream.
+ */
+private fun UIGestureRecognizer.isUINavigationControllerContentSwipeGestureRecognizer(): Boolean =
+    available(OS.Ios to OSVersion(major = 26)) &&
+        this is UIScreenEdgePanGestureRecognizer &&
+        className() == "_UIParallaxTransitionPanGestureRecognizer" &&
+        name == "UINavigationController.contentSwipe"
+
+@OptIn(BetaInteropApi::class)
+private fun NSObject.className() = this.`class`()?.let { NSStringFromClass(it) }

compose/ui/ui/src/uikitInstrumentedTest/kotlin/androidx/compose/ui/interop/UIKitNavigationSwipeBackTest.kt

@@ -0,0 +1,281 @@
+/*
+ * Copyright 2026 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.compose.ui.interop
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.systemBarsPadding
+import androidx.compose.foundation.pager.HorizontalPager
+import androidx.compose.foundation.pager.rememberPagerState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.MutableIntState
+import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.background
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.platform.testTag
+import androidx.compose.ui.test.UIKitInstrumentedTest
+import androidx.compose.ui.test.findNodeWithTag
+import androidx.compose.ui.test.findNodeWithTagOrNull
+import androidx.compose.ui.test.runUIKitInstrumentedTest
+import androidx.compose.ui.test.utils.center
+import androidx.compose.ui.test.utils.rightCenter
+import androidx.compose.ui.unit.dp
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlinx.cinterop.ExperimentalForeignApi
+import org.jetbrains.skiko.OS
+import org.jetbrains.skiko.OSVersion
+import org.jetbrains.skiko.available
+import platform.UIKit.UINavigationController
+import platform.UIKit.UIViewController
+
+@OptIn(ExperimentalForeignApi::class)
+internal abstract class UIKitNavigationSwipeBackTest(
+    private val runUIKitInstrumentedTest: (UIKitInstrumentedTest.() -> Unit) -> Unit
+) {
+    @Test
+    fun testSwipeRightOnPagerDoesNotPopController() = runUIKitInstrumentedTest {
+        val initialPage = 0
+        val currentPage = mutableIntStateOf(initialPage)
+
+        setNavigationControllerContent {
+            TestContent(currentPage = currentPage)
+        }
+
+        findNodeWithTag("pager").swipeRight()
+
+        waitForIdle()
+
+        assertEquals(2, navigationController.viewControllers.size)
+        assertNotNull(findNodeWithTagOrNull("pager"))
+        assertEquals(initialPage, currentPage.value)
+    }
+
+    @Test
+    fun testSwipeLeftOnPagerChangesPage() = runUIKitInstrumentedTest {
+        val initialPage = 0
+        val currentPage = mutableIntStateOf(initialPage)
+
+        setNavigationControllerContent {
+            TestContent(currentPage = currentPage)
+        }
+
+        findNodeWithTag("pager").swipeLeft()
+
+        waitForIdle()
+
+        assertEquals(initialPage + 1, currentPage.value)
+        assertEquals(2, navigationController.viewControllers.size)
+    }
+
+    @Test
+    fun testSwipeLeftOutsidePagerNoChanges() = runUIKitInstrumentedTest {
+        val initialPage = 1
+        val currentPage = mutableIntStateOf(initialPage)
+
+        setNavigationControllerContent {
+            TestContent(currentPage = currentPage)
+        }
+
+        findNodeWithTag("outsideBox").swipeLeft()
+
+        assertEquals(initialPage, currentPage.value)
+        assertEquals(2, navigationController.viewControllers.size)
+    }
+
+    @Test
+    fun testSwipeRightFromEdgePopsController() = runUIKitInstrumentedTest {
+        val viewControllerHostingCompose = setNavigationControllerContent {
+            TestContent(currentPage = mutableIntStateOf(1))
+        }
+
+        swipeRightFromEdge()
+
+        waitForPopped(viewControllerHostingCompose)
+    }
+
+    @Test
+    fun testSwipeRightFromCenterOutsidePagerDoesNotPopController() = runUIKitInstrumentedTest(
+        ignoreIf = available(OS.Ios to OSVersion(major = 26)),
+        ignoreNotes = "Full-width swipe gesture is not recognized on iOS < 26"
+    ){
+        val initialPage = 1
+        val currentPage = mutableIntStateOf(initialPage)
+
+        setNavigationControllerContent {
+            TestContent(currentPage = currentPage)
+        }
+
+        findNodeWithTag("outsideBox").swipe(
+            fromPosition = { center() },
+            toPosition = { rightCenter() },
+        )
+
+        waitForIdle()
+
+        assertNotNull(findNodeWithTagOrNull("pager"))
+        assertNotNull(findNodeWithTagOrNull("outsideBox"))
+        assertEquals(2, navigationController.viewControllers.size)
+    }
+
+    @Test
+    fun testSwipeRightOutsidePagerPopsControllerOnIos26() = runUIKitInstrumentedTest(
+        ignoreIf = !available(OS.Ios to OSVersion(major = 26)),
+        ignoreNotes = "Full-width swipe gesture is not recognized on iOS < 26"
+    ) {
+        val initialPage = 1
+        val currentPage = mutableIntStateOf(initialPage)
+
+        val viewControllerHostingCompose = setNavigationControllerContent {
+            TestContent(currentPage = currentPage)
+        }
+
+        findNodeWithTag("outsideBox").swipeRight()
+
+        waitForPopped(viewControllerHostingCompose)
+    }
+
+    @Test
+    fun testSwipeRightFromEdgeOutsidePagerPopsControllerOnIos26() = runUIKitInstrumentedTest(
+        ignoreIf = !available(OS.Ios to OSVersion(major = 26)),
+        ignoreNotes = "Full-width swipe gesture is not recognized on iOS < 26"
+    ) {
+        val initialPage = 1
+        val currentPage = mutableIntStateOf(initialPage)
+
+        val viewControllerHostingCompose = setNavigationControllerContent {
+            TestContent(currentPage = currentPage)
+        }
+
+        swipeRightFromEdge()
+
+        waitForPopped(viewControllerHostingCompose)
+    }
+
+    @Test
+    fun testSwipeRightFromCenterOutsidePagerPopsControllerOnIos26() = runUIKitInstrumentedTest(
+        ignoreIf = !available(OS.Ios to OSVersion(major = 26)),
+        ignoreNotes = "Full-width swipe gesture is not recognized on iOS < 26",
+    ) {
+        val initialPage = 1
+        val currentPage = mutableIntStateOf(initialPage)
+
+        val viewControllerHostingCompose = setNavigationControllerContent {
+            TestContent(currentPage = currentPage)
+        }
+
+        findNodeWithTag("outsideBox").swipe(
+            fromPosition = { center() },
+            toPosition = { rightCenter() },
+        )
+
+        waitForPopped(viewControllerHostingCompose)
+    }
+
+    private val UIKitInstrumentedTest.navigationController: UINavigationController get() {
+        return assertNotNull(appDelegate.window?.rootViewController as? UINavigationController)
+    }
+
+    private fun UIKitInstrumentedTest.setNavigationControllerContent(
+        content: @Composable () -> Unit = {}
+    ): UIViewController {
+        val viewControllerHostingCompose = createViewControllerHostingCompose(content = content)
+
+        setupWindow {
+            UINavigationController().also {
+                it.setViewControllers(listOf(UIViewController(), viewControllerHostingCompose), false)
+            }
+        }
+
+        waitUntil {
+            viewControllerHostingCompose.view.window != null
+        }
+
+        return viewControllerHostingCompose
+    }
+
+    private fun UIKitInstrumentedTest.waitForPopped(
+        viewController: UIViewController
+    ) {
+        waitUntil("Waiting for view controller to be popped and detached") {
+            navigationController.viewControllers.size == 1 &&
+                viewController.view.window == null
+        }
+    }
+
+    private fun runUIKitInstrumentedTest(
+        ignoreIf: Boolean,
+        ignoreNotes: String,
+        testBlock: UIKitInstrumentedTest.() -> Unit
+    ) = if (ignoreIf) {
+        println("Debug: Ignored test: $ignoreNotes")
+    } else {
+        runUIKitInstrumentedTest(testBlock)
+    }
+}
+
+@Composable
+private fun TestContent(
+    currentPage: MutableIntState
+) {
+    val pagerColors = listOf(Color.Red, Color.Green, Color.Blue)
+    val pagerState = rememberPagerState(initialPage = currentPage.value) { 3 }
+
+    LaunchedEffect(pagerState.currentPage) {
+        currentPage.value = pagerState.currentPage
+    }
+
+    Column(
+        modifier = Modifier
+            .fillMaxSize()
+            .systemBarsPadding()
+    ) {
+        HorizontalPager(
+            state = pagerState,
+            modifier = Modifier
+                .fillMaxWidth()
+                .weight(1f)
+                .testTag("pager")
+        ) { page ->
+            currentPage.value = page
+            Box(modifier = Modifier
+                .fillMaxSize()
+                .background(pagerColors[page])
+            )
+        }
+        Box(
+            modifier = Modifier
+                .fillMaxWidth()
+                .height(150.dp)
+                .testTag("outsideBox")
+        )
+    }
+}
+
+internal class UIKitNavigationSwipeBackInHostingViewTest : UIKitNavigationSwipeBackTest(
+    runUIKitInstrumentedTest = { runUIKitInstrumentedTest(useHostingView = true, it) }
+)
+
+internal class UIKitNavigationSwipeBackInHostingViewControllerTest : UIKitNavigationSwipeBackTest(
+   runUIKitInstrumentedTest = { runUIKitInstrumentedTest(useHostingView = false, it) }
+)