[WIP] PlatformTextInputService2

compose/foundation/foundation/src/skikoMain/kotlin/androidx/compose/foundation/text/input/internal/TextInputSession.skiko.kt

@@ -18,7 +18,9 @@ package androidx.compose.foundation.text.input.internal
 
 import androidx.compose.foundation.content.internal.ReceiveContentConfiguration
 import androidx.compose.foundation.text.computeSizeForDefaultText
+import androidx.compose.foundation.text.input.TextFieldBuffer
 import androidx.compose.foundation.text.input.TextFieldCharSequence
+import androidx.compose.foundation.text.input.delete
 import androidx.compose.foundation.text.input.setSelectionCoerced
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.ExperimentalComposeUiApi
@@ -30,19 +32,23 @@ import androidx.compose.ui.platform.PlatformTextInputMethodRequest
 import androidx.compose.ui.platform.PlatformTextInputSession
 import androidx.compose.ui.platform.ViewConfiguration
 import androidx.compose.ui.text.TextLayoutResult
+import androidx.compose.ui.text.TextRange
 import androidx.compose.ui.text.input.EditCommand
 import androidx.compose.ui.text.input.EditProcessor
 import androidx.compose.ui.text.input.ImeAction
 import androidx.compose.ui.text.input.ImeOptions
+import androidx.compose.ui.text.input.TextEditingScope
+import androidx.compose.ui.text.input.TextEditorState
 import androidx.compose.ui.text.input.TextFieldValue
 import androidx.compose.ui.unit.IntSize
+import kotlin.math.absoluteValue
+import kotlin.math.sign
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.callbackFlow
 import kotlinx.coroutines.flow.filterNotNull
-import kotlinx.coroutines.launch
 
-@OptIn(ExperimentalComposeUiApi::class)
 internal actual suspend fun PlatformTextInputSession.platformSpecificTextInputSession(
     state: TransformedTextFieldState,
     layoutState: TextLayoutState,
@@ -77,10 +83,19 @@ internal actual suspend fun PlatformTextInputSession.platformSpecificTextInputSe
         }
     }
 
+    fun editText(block: TextEditingScope.() -> Unit) {
+        state.editUntransformedTextAsUser {
+            with(TextEditingScope(this)) {
+                block()
+            }
+        }
+    }
+
     coroutineScope {
-        launch {
-            state.collectImeNotifications { _, newValue, _ ->
-                updateTextFieldValue(newValue.toTextFieldValue())
+        val outputValueFlow = callbackFlow {
+            state.collectImeNotifications { oldValue, newValue, restartIme ->
+                println("IME Notification: oldValue=$oldValue, newValue=$newValue, restartIme=$restartIme")
+                trySend(newValue.toTextFieldValue())
             }
         }
 
@@ -101,13 +116,16 @@ internal actual suspend fun PlatformTextInputSession.platformSpecificTextInputSe
 
         startInputMethod(
             SkikoPlatformTextInputMethodRequest(
-                state = state.untransformedText.toTextFieldValue(),
+                value = { state.untransformedText.toTextFieldValue() },
+                state = state.untransformedText.asTextEditorState(),
                 imeOptions = imeOptions,
                 onEditCommand = ::onEditCommand,
                 onImeAction = onImeAction,
                 editProcessor = editProcessor,
+                outputValue = outputValueFlow,
                 textLayoutResult = snapshotFlow(layoutState::layoutResult).filterNotNull(),
                 focusedRectInRoot = focusedRectInRootFlow,
+                editText = ::editText
             )
         )
     }
@@ -116,15 +134,154 @@ internal actual suspend fun PlatformTextInputSession.platformSpecificTextInputSe
 private fun TextFieldCharSequence.toTextFieldValue() =
     TextFieldValue(toString(), selection, composition)
 
+private fun TextFieldCharSequence.asTextEditorState() = object : TextEditorState {
+
+    override val length: Int
+        get() = this@asTextEditorState.length
+
+    override fun get(index: Int): Char = this@asTextEditorState[index]
+
+    override fun subSequence(startIndex: Int, endIndex: Int): CharSequence {
+        return this@asTextEditorState.subSequence(startIndex, endIndex)
+    }
+
+    override val selection: TextRange
+        get() = this@asTextEditorState.selection
+
+    override val composition: TextRange?
+        get() = this@asTextEditorState.composition
+
+}
+
+/**
+ * Helper function that returns true when [high] is a Unicode high-surrogate code unit and [low] is
+ * a Unicode low-surrogate code unit.
+ */
+private fun isSurrogatePair(high: Char, low: Char): Boolean =
+    high.isHighSurrogate() && low.isLowSurrogate()
+
+
+/**
+ * Returns the index, in characters, of the code point at distance [offset] from [index].
+ *
+ * If there aren't enough codepoints in the correct direction, returns 0 (if [offset] is negative)
+ * or the length of the char sequence (if [offset] is positive).
+ */
+private fun CharSequence.indexOfCodePointAtOffset(index: Int, offset: Int): Int {
+    val sign = offset.sign
+    val distance = offset.absoluteValue
+
+    var currentOffset = index
+    for (i in 0 until distance) {
+        currentOffset += sign
+        if (currentOffset <= 0) {
+            return 0
+        } else if (currentOffset >= length) {
+            return length
+        }
+
+
+        val lead = this[currentOffset - 1]
+        val trail = this[currentOffset]
+
+        if (isSurrogatePair(lead, trail)) {
+            currentOffset += sign
+        }
+    }
+
+    return currentOffset
+}
+
+
+private var TextFieldBuffer.cursor: Int
+    get() = if (selection.collapsed) selection.end else -1
+    set(value) {
+        setSelectionCoerced(value, value)
+    }
+
+private fun TextEditingScope(buffer: TextFieldBuffer) = object : TextEditingScope {
+
+    override fun deleteSurroundingTextInCodePoints(
+        lengthBeforeCursor: Int,
+        lengthAfterCursor: Int
+    ) {
+        val charSequence = buffer.asCharSequence()
+        val selection = buffer.selection
+        buffer.delete(
+            start = selection.end,
+            end = charSequence.indexOfCodePointAtOffset(
+                index = selection.end,
+                offset = lengthAfterCursor
+            )
+        )
+        buffer.delete(
+            start = charSequence.indexOfCodePointAtOffset(
+                index = selection.start,
+                offset = -lengthBeforeCursor
+            ),
+            end = selection.start
+        )
+    }
+
+    override fun commitText(text: CharSequence, newCursorPosition: Int) {
+        // API description says replace ongoing composition text if there. Then, if there is no
+        // composition text, insert text into cursor position or replace selection.
+        val replacementRange = buffer.composition ?: buffer.selection
+        buffer.replace(replacementRange.start, replacementRange.end, text)
+
+        // After replace function is called, the editing buffer places the cursor at the end of the
+        // modified range.
+        val newCursor = buffer.cursor
+
+        // See API description for the meaning of newCursorPosition.
+        val newCursorInBuffer =
+            if (newCursorPosition > 0) {
+                newCursor + newCursorPosition - 1
+            } else {
+                newCursor + newCursorPosition - text.length
+            }
+        buffer.setSelectionCoerced(newCursorInBuffer, newCursorInBuffer)
+    }
+
+    override fun setComposingText(text: CharSequence, newCursorPosition: Int) {
+        val replacementRange = buffer.composition ?: buffer.selection
+        // API doc says, if there is ongoing composing text, replace it with new text.
+        // If there is no composing text, insert composing text into cursor position with
+        // removing selected text if any.
+        buffer.replace(replacementRange.start, replacementRange.end, text)
+        if (text.isNotEmpty()) {
+            buffer.setComposition(replacementRange.start, replacementRange.start + text.length)
+        }
+
+        // After replace function is called, the editing buffer places the cursor at the end of the
+        // modified range.
+        val newCursor = buffer.cursor
+
+        // See API description for the meaning of newCursorPosition.
+        val newCursorInBuffer =
+            if (newCursorPosition > 0) {
+                newCursor + newCursorPosition - 1
+            } else {
+                newCursor + newCursorPosition - text.length
+            }
+
+        buffer.cursor = newCursorInBuffer
+    }
+}
+
+
 @OptIn(ExperimentalComposeUiApi::class)
 private data class SkikoPlatformTextInputMethodRequest(
-    override val state: TextFieldValue,
+    override val value: () -> TextFieldValue,
+    override val state: TextEditorState,
     override val imeOptions: ImeOptions,
     override val onEditCommand: (List<EditCommand>) -> Unit,
     override val onImeAction: ((ImeAction) -> Unit)?,
     override val editProcessor: EditProcessor?,
+    override val outputValue: Flow<TextFieldValue>,
     override val textLayoutResult: Flow<TextLayoutResult>,
-    override val focusedRectInRoot: Flow<Rect>
+    override val focusedRectInRoot: Flow<Rect>,
+    override val editText: (block: TextEditingScope.() -> Unit) -> Unit
 ): PlatformTextInputMethodRequest
 
 /**

compose/ui/ui-text/api/desktop/ui-text.api

@@ -1359,6 +1359,12 @@ public abstract interface class androidx/compose/ui/text/input/PlatformTextInput
 	public fun updateTextLayoutResult (Landroidx/compose/ui/text/input/TextFieldValue;Landroidx/compose/ui/text/input/OffsetMapping;Landroidx/compose/ui/text/TextLayoutResult;Lkotlin/jvm/functions/Function1;Landroidx/compose/ui/geometry/Rect;Landroidx/compose/ui/geometry/Rect;)V
 }
 
+public abstract interface class androidx/compose/ui/text/input/PlatformTextInputService2 {
+	public abstract fun focusedRectChanged (Landroidx/compose/ui/geometry/Rect;)V
+	public abstract fun startInput (Landroidx/compose/ui/text/input/TextEditorState;Landroidx/compose/ui/text/input/ImeOptions;Lkotlin/jvm/functions/Function1;)V
+	public abstract fun stopInput ()V
+}
+
 public final class androidx/compose/ui/text/input/SetComposingRegionCommand : androidx/compose/ui/text/input/EditCommand {
 	public static final field $stable I
 	public fun <init> (II)V
@@ -1394,6 +1400,17 @@ public final class androidx/compose/ui/text/input/SetSelectionCommand : androidx
 	public fun toString ()Ljava/lang/String;
 }
 
+public abstract interface class androidx/compose/ui/text/input/TextEditingScope {
+	public abstract fun commitText (Ljava/lang/CharSequence;I)V
+	public abstract fun deleteSurroundingTextInCodePoints (II)V
+	public abstract fun setComposingText (Ljava/lang/CharSequence;I)V
+}
+
+public abstract interface class androidx/compose/ui/text/input/TextEditorState : java/lang/CharSequence {
+	public abstract fun getComposition-MzsxiRA ()Landroidx/compose/ui/text/TextRange;
+	public abstract fun getSelection-d9O1mEE ()J
+}
+
 public final class androidx/compose/ui/text/input/TextFieldValue {
 	public static final field $stable I
 	public static final field Companion Landroidx/compose/ui/text/input/TextFieldValue$Companion;

compose/ui/ui-text/src/skikoMain/kotlin/androidx/compose/ui/text/input/PlatformTextInputService2.kt

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2025 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.text.input
+
+import androidx.compose.ui.geometry.Rect
+import androidx.compose.ui.text.TextRange
+
+interface TextEditorState : CharSequence {
+
+    val selection: TextRange
+    val composition: TextRange?
+
+}
+
+interface TextEditingScope {
+    /**
+     * Deletes text around the cursor.
+     *
+     * This intends to replicate [DeleteSurroundingTextInCodePointsCommand] for
+     * [PlatformTextInputService2].
+     */
+    fun deleteSurroundingTextInCodePoints(lengthBeforeCursor: Int, lengthAfterCursor: Int)
+
+    /**
+     * Commits text and repositions the cursor.
+     *
+     * This intends to replicate [CommitTextCommand] for [PlatformTextInputService2].
+     */
+    fun commitText(text: CharSequence, newCursorPosition: Int)
+
+    /**
+     * Sets the composing text and repositions the cursor.
+     *
+     * This intends to replicate [SetComposingTextCommand] for [PlatformTextInputService2].
+     */
+    fun setComposingText(text: CharSequence, newCursorPosition: Int)
+}
+
+interface PlatformTextInputService2 {
+
+    fun startInput(
+        state: TextEditorState,
+        imeOptions: ImeOptions,
+        editText: (block: TextEditingScope.() -> Unit) -> Unit,
+    )
+
+    fun stopInput()
+
+    fun focusedRectChanged(rect: Rect)
+
+}

compose/ui/ui/api/desktop/ui.api

@@ -3584,12 +3584,15 @@ public abstract interface class androidx/compose/ui/platform/PlatformTextInputIn
 
 public abstract interface class androidx/compose/ui/platform/PlatformTextInputMethodRequest {
 	public abstract fun getEditProcessor ()Landroidx/compose/ui/text/input/EditProcessor;
+	public abstract fun getEditText ()Lkotlin/jvm/functions/Function1;
 	public abstract fun getFocusedRectInRoot ()Lkotlinx/coroutines/flow/Flow;
 	public abstract fun getImeOptions ()Landroidx/compose/ui/text/input/ImeOptions;
 	public abstract fun getOnEditCommand ()Lkotlin/jvm/functions/Function1;
 	public abstract fun getOnImeAction ()Lkotlin/jvm/functions/Function1;
-	public abstract fun getState ()Landroidx/compose/ui/text/input/TextFieldValue;
+	public abstract fun getOutputValue ()Lkotlinx/coroutines/flow/Flow;
+	public abstract fun getState ()Landroidx/compose/ui/text/input/TextEditorState;
 	public abstract fun getTextLayoutResult ()Lkotlinx/coroutines/flow/Flow;
+	public abstract fun getValue ()Lkotlin/jvm/functions/Function0;
 }
 
 public abstract interface class androidx/compose/ui/platform/PlatformTextInputModifierNode : androidx/compose/ui/node/DelegatableNode {
@@ -3602,7 +3605,6 @@ public final class androidx/compose/ui/platform/PlatformTextInputModifierNodeKt
 
 public abstract interface class androidx/compose/ui/platform/PlatformTextInputSession {
 	public abstract fun startInputMethod (Landroidx/compose/ui/platform/PlatformTextInputMethodRequest;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
-	public fun updateTextFieldValue (Landroidx/compose/ui/text/input/TextFieldValue;)V
 }
 
 public abstract interface class androidx/compose/ui/platform/PlatformTextInputSessionScope : androidx/compose/ui/platform/PlatformTextInputSession, kotlinx/coroutines/CoroutineScope {

compose/ui/ui/src/desktopMain/kotlin/androidx/compose/ui/platform/DesktopPlatformInput.desktop.kt

@@ -104,7 +104,7 @@ internal class DesktopTextInputService(private val component: PlatformComponent)
     }
 
     fun inputMethodTextChanged(event: InputMethodEvent) {
-        if (!event.isConsumed) {
+        if ((currentInput != null) && !event.isConsumed) {
             replaceInputMethodText(event)
             event.consume()
         }