[web] Refactor inner implementation of web input by Schahen · Pull Request #2838 · JetBrains/compose-multiplatform-core

Schahen · 2026-03-09T16:29:03Z

Following changes are introduced:

Reschedule checkpoint after successful NativeInputEventsProcessor::runCheckpoint run
Reduce amount of expect/actual implementations (in favour of using entities in webMain)
ComposeCommandCommunicator::sendKeyboardEvent return boolean which indicates whethre compose actually processed event (this logic used for finer Backspace resolution)

Testing

manual and gradlew testWeb

Release Notes

N/A

Following changes are introduced: * Reschedule checkpoint after successful NativeInputEventsProcessor::runCheckpoint run * Reduce amount of expect/actual implementations (in favour of using entities in webMain) * ComposeCommandCommunicator::sendKeyboardEvent return boolean which indicates whethre compose actually processed event (this logic used for finer Backspace resolution)

Copilot

Pull request overview

Refactors the web text input pipeline to reduce platform-specific implementations, improve checkpoint scheduling behavior, and make keyboard event handling aware of whether Compose actually consumed an event (for more accurate Backspace resolution).

Changes:

Updates web text input startup to pass a PlatformTextInputMethodRequest through to the web service implementation.
Refactors native DOM event processing (checkpointing + Backspace/beforeinput interplay) and removes timestamp interop expect/actual utilities.
Changes ComposeCommandCommunicator.sendKeyboardEvent to return a Boolean indicating whether Compose handled the event, and adapts call sites/tests.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
compose/ui/ui/src/webTest/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessorTest.kt	Updates mock communicator to return `Boolean` from `sendKeyboardEvent`.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/window/WebTextInputSession.kt	Switches to starting input via `webTextInputService.startInput(request)`.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/WebTextInputService.kt	Introduces request-based `startInput` and adapts communicator keyboard event return type.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessor.kt	Refactors event processing and uses keyboard-event consumption result to refine beforeinput Backspace handling.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/DomInputStrategy.kt	Simplifies input event interop and tightens “Compose-only” key handling in keydown.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/BackingDomInput.kt	Updates communicator API to return `Boolean` from `sendKeyboardEvent`.
compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/internal/jsinterop/JsInteropUtils.kt	Removes timestamp expect/actual utilities.
compose/ui/ui/src/wasmJsMain/kotlin/androidx/compose/ui/platform/DomInputStrategy.wasmJs.kt	Removes wasmJs actual for `asInputEventExt`.
compose/ui/ui/src/wasmJsMain/kotlin/androidx/compose/ui/internal/jsinterop/JsInteropUtils.wasmJs.kt	Removes wasmJs actual timestamp utilities.
compose/ui/ui/src/jsMain/kotlin/androidx/compose/ui/platform/DomInputStrategy.js.kt	Removes js actual for `asInputEventExt`.
compose/ui/ui/src/jsMain/kotlin/androidx/compose/ui/internal/jsinterop/JsInteropUtils.js.kt	Removes js actual timestamp utilities.
compose/foundation/foundation/src/webMain/kotlin/androidx/compose/foundation/text/TextFieldKeyInput.web.kt	Refactors typed-event detection to rely on the DOM keyboard event flags.

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compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessor.kt

Copilot · 2026-03-09T16:35:11Z

compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessor.kt

+        isInIMEComposition = false
        collectedEvents.clear()
+        isCheckpointScheduled = true
    }


At the end of runCheckpoint() the code sets isCheckpointScheduled = true after clearing events. With the current scheduling logic this can prevent future checkpoints from being scheduled after this run. Typically the flag should be cleared when the scheduled checkpoint starts running, and only set when a new checkpoint is actually scheduled (not unconditionally at the end of processing).

Setting isCheckpointScheduled = true is not correct.
It should be set in:

if (!isCheckpointScheduled) { scheduleCheckpoint() // here: isCheckpointScheduled = true }

Are you sure? I might be missing something - mine approach is most likely wrong - but this way - won't we end up with immidiately resetting checkpoing while in scheduleCheckpoint something is still runinng in requestAnimationFrame?

the idea of setting isCheckpointScheduled = true in

if (!isCheckpointScheduled) { scheduleCheckpoint() isCheckpointScheduled = true }

is to avoid having more than one call to scheduleCheckpoint until the checkpoint is executed.

It should be reset back to false isCheckpointScheduled = false in fun runCheckpoint(currentTextFieldValue: TextFieldValue)

Copilot · 2026-03-09T16:35:11Z

compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessor.kt

+class ComposeKeyDownStatus(
+    val event: KeyboardEvent,
+    val processed: Boolean
+)


ComposeKeyDownStatus is declared as a public top-level class but is only used inside NativeInputEventsProcessor.kt. Making it public expands the module’s API surface unnecessarily; it should be private (or at most internal) and ideally a private data class if it’s just a value holder.

Copilot · 2026-03-09T16:35:12Z

compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/WebTextInputService.kt

+    override fun startInput(
+        value: TextFieldValue,
+        imeOptions: ImeOptions,
+        onEditCommand: (List<EditCommand>) -> Unit,
+        onImeActionPerformed: (ImeAction) -> Unit
+    ) {
+        // This method is not used in the new API, but we keep it for backward compatibility.
+    }


The overridden startInput(value, imeOptions, onEditCommand, onImeActionPerformed) is currently a no-op, which breaks the PlatformTextInputService contract for any code path still using the legacy API. If this is truly kept for backward compatibility, it should delegate to the new startInput(request) (by adapting the parameters) or preserve the previous behavior instead of doing nothing.

Copilot · 2026-03-09T16:35:12Z

compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessor.kt

+                        lastKeydownStatus = ComposeKeyDownStatus(
+                            evt,
+                            composeSender.sendKeyboardEvent(evt.toComposeEvent())
+                        )


New behavior relies on the boolean result of composeSender.sendKeyboardEvent(...) (stored in lastKeydownStatus) to decide whether to ignore a subsequent deleteContentBackward. There isn’t a test covering the processed = false path (i.e., when Compose doesn’t consume Backspace and the beforeinput should still generate commands). Add a unit test with a communicator that returns false from sendKeyboardEvent and assert that deleteContentBackward is handled.

eymar · 2026-03-09T16:35:51Z

compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/DomInputStrategy.kt

            }
        })

-        htmlInput.addEventListener("compositionstart", { evt ->


isInIMEComposition includes compositionstart, so I think this event listener should remain here?

updated this logic - basically, we need to register this event but don't care about any handlers

…i:compileWebMainKotlinMetadata

…rocessing compositionstart and compositionupdate

eymar · 2026-03-10T08:31:40Z

...tion/foundation/src/webMain/kotlin/androidx/compose/foundation/text/TextFieldKeyInput.web.kt

+    get() = isTypedEvent(this)
+
+private fun isTypedEvent(evt: KeyboardEvent): Boolean =
+    js("!evt.metaKey && !evt.ctrlKey && evt.key.charAt(0) === evt.key")


So now we have 3 different declarations.

We can't avoid implementing the expect/actual and we can't avoid extracting the js calls into a separate function.

But do we need private val KeyboardEvent.isTypedEvent: Boolean?

I think 2 declarations would be enough. WDYT?

eymar · 2026-03-10T08:40:49Z

compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessor.kt

                        // we need to reset this each time we consider something to be typed
                        // see  https://youtrack.jetbrains.com/issue/CMP-8773
-                        lastProcessedEventIsBackspace = evt.key == "Backspace"
+                        lastKeydownStatus = null


lastProcessedEventIsBackspace = evt.key == "Backspace" has been added here #2559 as a fix for iOS.

But now lastProcessedEventIsBackspace = evt.key == "Backspace" is removed. Won't it cause a regression on iOS?

eymar · 2026-03-10T08:57:26Z

compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/platform/NativeInputEventsProcessor.kt

+        val editCommands = buildList {
+            when (inputType) {
+                "deleteContentBackward" -> {
+                    if (lastKeydownStatus?.getProcessedEvent()?.isBackspace() == true) return@buildList


I think the simple bolean lastProcessedEventIsBackspace check looked more readable than the chain of nullable calls with the same result.

Do we need lastKeydownStatus for anything else or only for this specific check?

Simple Boolean lastProcessedEventIsBackspace does not take into account that compose indeed processed this event

but it can take it into account if it's set to true only when compose actually handled it, right?

Schahen requested review from Copilot and eymar March 9, 2026 16:29

Copilot started reviewing on behalf of Schahen March 9, 2026 16:31 View session

Copilot AI reviewed Mar 9, 2026

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eymar reviewed Mar 9, 2026

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Schahen added 4 commits March 9, 2026 17:52

Fix InputEventExt definition to make it compatible with :compose:ui:u…

5130e14

…i:compileWebMainKotlinMetadata

ComposeKeyDownStatus is private

e93d1e6

Introduce nativeInputEventsProcessor updateImeStatus and use it for p…

3e5bd54

…rocessing compositionstart and compositionupdate

reset isCheckpointScheduled in internalScheduleCheckpoint

061208c

eymar reviewed Mar 10, 2026

View reviewed changes

Port fixes from jb-main

73e379d

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Schahen commented Mar 9, 2026 •

edited

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