[web] Improve faste delete experience by Schahen · Pull Request #2954 · JetBrains/compose-multiplatform-core

Schahen · 2026-04-08T16:17:39Z

Fix the exceptions thrown on attempting fast delete in empty strings
ComposeCommandCommunicator is TextLayoutResult-agnostic

Testing

manual + ./gradlew testWeb

Release Notes

Fixes - Web

CMP-9971 [Web] Mobile. iOS. Crash when using 'Fast delete'. Cannot coerce value to an empty range: maximum -1 is less than minimum 0

* Fix the exceptions thrown on attempting faste delete in empty strings * ComposeCommandCommunicator is TextLayoutResult-agnostic

Copilot

Pull request overview

This PR targets the Web text input pipeline to prevent crashes during “fast delete” on empty strings, and refactors the event-processing stack so the command-sending interface is no longer coupled to TextLayoutResult.

Changes:

Refactors native input event processing to use a separate TextLayoutProvider (instead of adding layout access to ComposeCommandCommunicator).
Updates Web text input session/service wiring to pass initial TextFieldValue + IME callbacks and to provide a text layout result accessor.
Moves DOM element creation (ImeOptions.createDomElement) from DomInputStrategy into BackingDomInput.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
compose/ui/ui/src/webTest/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessorTest.kt	Updates unit test scaffolding for the refactored `NativeInputEventsProcessor` API.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/window/WebTextInputSession.kt	Adapts session startup to the new `startInput` signature and wires a layout-result provider into the service.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/WebTextInputService.kt	Implements the new `startInput` override and routes layout-result requests via a stored provider lambda.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessor.kt	Implements the fast-delete behavior changes and decouples command dispatch via a sender context + layout provider.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/DomInputStrategy.kt	Makes DOM input strategy layout-aware via `TextLayoutProvider` and updates event processing construction.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/BackingDomInput.kt	Introduces `TextLayoutProvider`, makes backing input layout-aware, and relocates DOM element creation.

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Copilot · 2026-04-08T16:22:18Z

        if (currentOffset <= 0) {
            return 0
        }
        val text = layoutInput.text
-        val currentWord = getWordBoundary(currentOffset.coerceIn(0, text.length - 1))
+        val currentWord = getWordBoundary(currentOffset.coerceAtMost(text.length - 1))
        return if (currentWord.start >= currentOffset) {
            getPrevWordOffset(currentOffset - 1)
        } else {
-            OffsetMapping.Identity.transformedToOriginal(currentWord.start)
+            offsetMapping.transformedToOriginal(currentWord.start)
        }


getPrevWordOffset can still crash when the text is empty. When text.length == 0, text.length - 1 is -1, so currentOffset.coerceAtMost(-1) yields -1 and getWordBoundary(-1) is invalid. Add an explicit empty-text guard (e.g., return 0 when text.isEmpty()) before calling getWordBoundary.

Copilot · 2026-04-08T16:22:18Z

-        val currentWord = getWordBoundary(currentOffset.coerceIn(0, text.length - 1))
+        val currentWord = getWordBoundary(currentOffset.coerceAtMost(text.length - 1))
        return if (currentWord.start >= currentOffset) {
            getPrevWordOffset(currentOffset - 1)


getPrevWordOffset drops the provided offsetMapping on the recursive call (getPrevWordOffset(currentOffset - 1)), which makes the result inconsistent when a non-identity mapping is passed. Pass the same offsetMapping through the recursion to keep the mapping behavior correct.

Suggested change

getPrevWordOffset(currentOffset - 1)

getPrevWordOffset(currentOffset - 1, offsetMapping)

Copilot · 2026-04-08T16:22:18Z

        suspendCancellableCoroutine<Nothing> { continuation ->
            webTextInputService.startInput(
-                request,
-                onEditCommand = request.onEditCommand
+                value = request.value(),
+                imeOptions = request.imeOptions,
+                onEditCommand = request.onEditCommand,
+                onImeActionPerformed = request.onImeAction ?: {}
            )

+            webTextInputService.currentTextLayoutResult = request.textLayoutResult
+


currentTextLayoutResult is set only after startInput(...) returns. Since startInput focuses/registers the backing element, input events could be delivered before this property is set, making fast-delete word handling a no-op (or relying on timing). Consider setting webTextInputService.currentTextLayoutResult before calling startInput(...).

Copilot · 2026-04-08T16:22:19Z

@@ -79,11 +83,13 @@ internal abstract class WebTextInputService :
                override fun sendEditCommand(commands: List<EditCommand>) {
                    onEditCommand(commands)
                }
-
-                override fun currentTextLayoutResult() = request.textLayoutResult()
            },
            inputContainer = backingDomInputContainer,
-        )
+        ) {
+            override fun currentTextLayoutResult(): TextLayoutResult? =
+                this@WebTextInputService.currentTextLayoutResult?.invoke()
+        }
+
        backingDomInput?.register()

        if (currentTouchOffset != null) {
@@ -96,21 +102,12 @@ internal abstract class WebTextInputService :
        showSoftwareKeyboard()
    }


startInput receives an initial value: TextFieldValue but never applies it to the backing DOM input. This can leave the backing element briefly out of sync until updateState runs, and it also makes the value parameter effectively unused. Consider calling backingDomInput?.updateState(value) (or equivalent initialization) before focusing/showing the keyboard.

Copilot · 2026-04-08T16:22:19Z

+        setProperty("width", "calc(var(--compose-internal-web-backing-input-width) * 1px")
+        setProperty("height", "calc(var(--compose-internal-web-backing-input-height) * 1px")


The CSS calc(...) strings for width/height are missing a closing ) (e.g., "calc(var(--compose-internal-web-backing-input-width) * 1px"). This makes the style value invalid and may prevent the backing input from being sized/positioned correctly. Add the missing closing parenthesis to both properties.

Suggested change

setProperty("width", "calc(var(--compose-internal-web-backing-input-width) * 1px")

setProperty("height", "calc(var(--compose-internal-web-backing-input-height) * 1px")

setProperty("width", "calc(var(--compose-internal-web-backing-input-width) * 1px)")

setProperty("height", "calc(var(--compose-internal-web-backing-input-height) * 1px)")

Copilot · 2026-04-08T16:22:19Z

+        }
+
+        override fun currentTextLayoutResult(): TextLayoutResult? {
+            TODO("currentTextLayoutResult is tested in integration tests")


Using TODO(...) for currentTextLayoutResult() in the unit-test processor can cause unrelated tests to crash if any new/updated test triggers the deleteWordBackward path. Returning null (or a minimal stub TextLayoutResult) would keep the tests resilient while still deferring full coverage to integration tests.

Suggested change

TODO("currentTextLayoutResult is tested in integration tests")

return null

…2961) This is minimal version of the [PR-2954](#2954) ## Testing manual and `./gradlew testWeb` ## Release Notes ### Fixes - Web - [CMP-9971](https://youtrack.jetbrains.com/issue/CMP-9971) [Web] Mobile. iOS. Crash when using 'Fast delete'. Cannot coerce value to an empty range: maximum -1 is less than minimum 0

[web] Improve faste delete experience

27ad9e1

* Fix the exceptions thrown on attempting faste delete in empty strings * ComposeCommandCommunicator is TextLayoutResult-agnostic

Schahen requested review from Copilot and eymar April 8, 2026 16:17

Copilot AI reviewed Apr 8, 2026

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Schahen mentioned this pull request Apr 9, 2026

Fix the exceptions thrown on attempting fast delete in empty strings #2961

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[web] Improve faste delete experience#2954

[web] Improve faste delete experience#2954
Schahen wants to merge 1 commit intojb-mainfrom
sh/web_fast_delete_second_iteration

Schahen commented Apr 8, 2026 •

edited

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	getPrevWordOffset(currentOffset - 1)
	getPrevWordOffset(currentOffset - 1, offsetMapping)

		setProperty("width", "calc(var(--compose-internal-web-backing-input-width) * 1px")
		setProperty("height", "calc(var(--compose-internal-web-backing-input-height) * 1px")

	TODO("currentTextLayoutResult is tested in integration tests")
	return null

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Schahen commented Apr 8, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Testing

Release Notes

Fixes - Web

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Schahen commented Apr 8, 2026 •

edited

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