Fix iOS word selection for CJK text

compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/text/selection/SelectionAdjustment.kt

@@ -288,11 +288,11 @@ private fun SelectableInfo.snapToWordBoundary(
     return anchorForOffset(resultOffset)
 }
 
-private fun interface BoundaryFunction {
+internal fun interface BoundaryFunction {
     fun SelectableInfo.getBoundary(offset: Int): TextRange
 }
 
-private fun adjustToBoundaries(
+internal fun adjustToBoundaries(
     layout: SelectionLayout,
     boundaryFunction: BoundaryFunction,
 ): Selection {

compose/foundation/foundation/src/iosMain/kotlin/androidx/compose/foundation/text/TextFieldPointerModifier.ios.kt

@@ -17,6 +17,7 @@
 package androidx.compose.foundation.text
 
 import androidx.compose.foundation.interaction.MutableInteractionSource
+import androidx.compose.foundation.text.selection.IosWordSelectionAdjustment
 import androidx.compose.foundation.text.selection.TextFieldSelectionManager
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
@@ -40,4 +41,5 @@ internal actual fun Modifier.textFieldPointer(
     focusRequester,
     readOnly,
     offsetMapping,
-)
+    IosWordSelectionAdjustment,
+)

compose/foundation/foundation/src/iosMain/kotlin/androidx/compose/foundation/text/input/internal/selection/TextFieldSelectionState.ios.kt

@@ -40,6 +40,7 @@ import androidx.compose.foundation.text.input.internal.selection.TextFieldSelect
 import androidx.compose.foundation.text.input.internal.selection.TextToolbarState.Cursor
 import androidx.compose.foundation.text.input.internal.selection.TextToolbarState.None
 import androidx.compose.foundation.text.input.internal.selection.TextToolbarState.Selection
+import androidx.compose.foundation.text.selection.IosWordSelectionAdjustment
 import androidx.compose.foundation.text.selection.MouseSelectionObserver
 import androidx.compose.foundation.text.selection.SelectionAdjustment
 import androidx.compose.foundation.text.selection.awaitSelectionGestures
@@ -243,12 +244,18 @@ private fun TextFieldSelectionState.doRepeatingTapSelection(
         position = touchPointOffset
     )
 
+    val effectiveAdjustment =
+        if (selectionAdjustment == SelectionAdjustment.Word) {
+            IosWordSelectionAdjustment
+        } else {
+            selectionAdjustment
+        }
     val newSelection = updateSelection(
         textFieldState.visualText,
         selectionOffset,
         selectionOffset,
         isStartHandle = false,
-        adjustment = selectionAdjustment,
+        adjustment = effectiveAdjustment,
         hapticFeedbackType = HapticFeedbackType.TextHandleMove,
     )
 

compose/foundation/foundation/src/iosMain/kotlin/androidx/compose/foundation/text/selection/IosWordSelectionAdjustment.ios.kt

@@ -0,0 +1,48 @@
+/*
+ * 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.foundation.text.selection
+
+import androidx.compose.ui.text.TextRange
+import kotlinx.cinterop.ExperimentalForeignApi
+import kotlinx.cinterop.useContents
+import platform.NaturalLanguage.NLTokenUnit
+import platform.NaturalLanguage.NLTokenizer
+
+internal val IosWordSelectionAdjustment = SelectionAdjustment { layout ->
+    adjustToBoundaries(layout) { offset ->
+        iosWordBoundary(inputText, offset) ?: textLayoutResult.getWordBoundary(offset)
+    }
+}
+
+@OptIn(ExperimentalForeignApi::class)
+internal fun iosWordBoundary(text: String, offset: Int): TextRange? {
+    if (text.isEmpty()) return null
+
+    val tokenizer = NLTokenizer(NLTokenUnit.NLTokenUnitWord)
+    tokenizer.string = text
+    val index = offset.coerceIn(0, text.lastIndex).toULong()
+
+    return tokenizer.tokenRangeAtIndex(index).useContents {
+        if (length == 0uL || location >= text.length.toULong()) {
+            null
+        } else {
+            val start = location.toInt()
+            val end = (location + length).coerceAtMost(text.length.toULong()).toInt()
+            TextRange(start, end)
+        }
+    }
+}

compose/foundation/foundation/src/iosTest/kotlin/androidx/compose/foundation/text/selection/IosWordSelectionAdjustmentTest.kt

@@ -0,0 +1,49 @@
+/*
+ * 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.foundation.text.selection
+
+import androidx.compose.ui.text.TextRange
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+
+class IosWordSelectionAdjustmentTest {
+    @Test
+    fun chineseUsesLinguisticWordBoundary() {
+        assertEquals(TextRange(4, 6), iosWordBoundary("我在学习中文", 5))
+    }
+
+    @Test
+    fun japaneseUsesLinguisticWordBoundary() {
+        assertEquals(TextRange(3, 5), iosWordBoundary("これは日本語です", 4))
+    }
+
+    @Test
+    fun cjkAfterEmojiUsesUtf16Offsets() {
+        assertEquals(TextRange(6, 8), iosWordBoundary("😀我在学习中文", 7))
+    }
+
+    @Test
+    fun latinUsesLinguisticWordBoundary() {
+        assertEquals(TextRange(10, 18), iosWordBoundary("this is a language", 12))
+    }
+
+    @Test
+    fun whitespaceFallsBackToLayoutBoundary() {
+        assertNull(iosWordBoundary("word word", 4))
+    }
+}

compose/foundation/foundation/src/skikoMain/kotlin/androidx/compose/foundation/text/CupertinoTextFieldPointerModifier.skiko.kt

@@ -45,7 +45,8 @@ internal fun Modifier.cupertinoTextFieldPointer(
     state: LegacyTextFieldState,
     focusRequester: FocusRequester,
     readOnly: Boolean,
-    offsetMapping: OffsetMapping
+    offsetMapping: OffsetMapping,
+    wordSelectionAdjustment: SelectionAdjustment = SelectionAdjustment.Word,
 ): Modifier = if (enabled) {
     this
         .updateSelectionTouchMode { state.isInTouchMode = it }
@@ -84,7 +85,14 @@ internal fun Modifier.cupertinoTextFieldPointer(
                 state.handleState = HandleState.Cursor
             }
         }
-        .then(CupertinoSelectionGesturesModifierElement(manager, state, offsetMapping))
+        .then(
+            CupertinoSelectionGesturesModifierElement(
+                manager,
+                state,
+                offsetMapping,
+                wordSelectionAdjustment,
+            )
+        )
         .pointerHoverIcon(PointerIcon.Text)
 } else {
     this
@@ -94,12 +102,18 @@ private data class CupertinoSelectionGesturesModifierElement(
     private val manager: TextFieldSelectionManager,
     private val state: LegacyTextFieldState,
     private val offsetMapping: OffsetMapping,
+    private val wordSelectionAdjustment: SelectionAdjustment,
 ) : ModifierNodeElement<CupertinoSelectionGesturesModifierNode>() {
     override fun create(): CupertinoSelectionGesturesModifierNode =
-        CupertinoSelectionGesturesModifierNode(manager, state, offsetMapping)
+        CupertinoSelectionGesturesModifierNode(
+            manager,
+            state,
+            offsetMapping,
+            wordSelectionAdjustment,
+        )
 
     override fun update(node: CupertinoSelectionGesturesModifierNode) {
-        node.update(manager, state, offsetMapping)
+        node.update(manager, state, offsetMapping, wordSelectionAdjustment)
     }
 
     override fun InspectorInfo.inspectableProperties() {
@@ -111,6 +125,7 @@ private class CupertinoSelectionGesturesModifierNode(
     private var manager: TextFieldSelectionManager,
     private var state: LegacyTextFieldState,
     private var offsetMapping: OffsetMapping,
+    private var wordSelectionAdjustment: SelectionAdjustment,
 ) : DelegatingNode() {
     private val longPressDragObserver = object : TextDragObserver {
         var dragTotalDistance = Offset.Zero
@@ -138,7 +153,13 @@ private class CupertinoSelectionGesturesModifierNode(
                     state.onValueChange
                 )
                 if (selectionAdjustment != SelectionAdjustment.None) {
-                    manager.doRepeatingTapSelection(startPoint, selectionAdjustment)
+                    val effectiveAdjustment =
+                        if (selectionAdjustment == SelectionAdjustment.Word) {
+                            wordSelectionAdjustment
+                        } else {
+                            selectionAdjustment
+                        }
+                    manager.doRepeatingTapSelection(startPoint, effectiveAdjustment)
                 }
                 dragBeginOffset = startPoint
             }
@@ -196,13 +217,15 @@ private class CupertinoSelectionGesturesModifierNode(
         manager: TextFieldSelectionManager,
         state: LegacyTextFieldState,
         offsetMapping: OffsetMapping,
+        wordSelectionAdjustment: SelectionAdjustment,
     ) {
         if (this.manager != manager) {
             pointerInputNode.resetPointerInputHandler()
         }
         this.manager = manager
         this.state = state
         this.offsetMapping = offsetMapping
+        this.wordSelectionAdjustment = wordSelectionAdjustment
     }
 }