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Fix re-entrance in draw function #2756

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Merged
ASalavei merged 7 commits into from
Feb 16, 2026
Merged

Fix re-entrance in draw function #2756

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52b73e8
Fix re-entrance in draw function
ASalavei Feb 11, 2026
c2d0018
Use check
ASalavei Feb 11, 2026
62557a4
Remove typo
ASalavei Feb 11, 2026
57cf4da
Fix return
ASalavei Feb 11, 2026
201536b
Fix tests
ASalavei Feb 11, 2026
cea993f
Remove unused code
ASalavei Feb 12, 2026
e0fae12
Try-finally
ASalavei Feb 13, 2026
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3 changes: 0 additions & 3 deletions ...ose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/scene/ComposeLayersViewController.ios.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -180,9 +180,6 @@ internal class ComposeLayersViewController(
hide()

transaction.actions.fastForEach { it.invoke() }

// If the layers list is empty, the draw call will clear the canvas.
metalView.redrawer.draw(waitUntilCompletion = false)
} else {
// It wasn't the last layer, pending transactions should be added to the list
removedLayersTransactions.add(transaction)
Expand Down
1 change: 1 addition & 0 deletions compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/window/ComposeContainerView.ios.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,7 @@ internal class ComposeContainerView(
onDidMoveToWindow(window)

updateRedrawerState()
setNeedsSynchronousDraw()

// To avoid a situation where a user decided to call [layoutIfNeeded] on the detached view
// using a certain frame and it will be attached to the window later, so there is a chance
Expand Down
244 changes: 129 additions & 115 deletions compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/window/MetalRedrawer.ios.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -128,6 +128,8 @@ internal class MetalRedrawer(

private val inflightCommandBuffersGroup = dispatch_group_create()
private val drawCanvasSemaphore = dispatch_semaphore_create(1)
// A guard flag to have proper assertion when draw() method is called recursively.
private var isDrawRecursiveCall = false

var isForcedToPresentWithTransactionEveryFrame = false

Expand Down Expand Up @@ -319,153 +321,165 @@ internal class MetalRedrawer(
@OptIn(BetaInteropApi::class)
private fun draw(waitUntilCompletion: Boolean, targetTimestamp: NSTimeInterval) = trace("MetalRedrawer:draw") {
check(NSThread.isMainThread)
check(!isDrawRecursiveCall) {
"Attempt to call MetalRedrawer.draw() recursively which may lead to the PictureRecorder corruption."
}
isDrawRecursiveCall = true

lastRenderTimestamp = maxOf(targetTimestamp, lastRenderTimestamp)

autoreleasepool {
val (width, height) = metalLayer.drawableSize.useContents {
width.roundToInt() to height.roundToInt()
}

if (width <= 0 || height <= 0) {
return@autoreleasepool
}
try {
lastRenderTimestamp = maxOf(targetTimestamp, lastRenderTimestamp)

// Perform timestep and record all draw commands into [Picture]
val picture = trace("MetalRedrawer:draw:pictureRecording") {
pictureRecorder.beginRecording(
left = 0f,
top = 0f,
width.toFloat(),
height.toFloat()
).also { canvas ->
render(canvas, lastRenderTimestamp)
autoreleasepool {
val (width, height) = metalLayer.drawableSize.useContents {
width.roundToInt() to height.roundToInt()
}

pictureRecorder.finishRecordingAsPicture()
}

if (!currentFrameRate.isNaN()) {
preferredFramesPerSecond = currentFrameRate.toLong()
currentFrameRate = Float.NaN
}

val metalDrawable = trace("MetalRedrawer:draw:nextDrawable") {
metalDrawablesHandler.nextDrawable()
}

if (metalDrawable == null) {
// TODO: anomaly, log
// Logger.warn { "'metalLayer.nextDrawable()' returned null. 'metalLayer.allowsNextDrawableTimeout' should be set to false. Skipping the frame." }
picture.close()
return@autoreleasepool
}

val renderTarget = BackendRenderTarget.makeMetal(
width,
height,
texturePtr = metalDrawablesHandler.drawableTexture(metalDrawable).rawValue
)
if (width <= 0 || height <= 0) {
return@autoreleasepool
}

val surface = Surface.makeFromBackendRenderTarget(
context,
renderTarget,
SurfaceOrigin.TOP_LEFT,
SurfaceColorFormat.BGRA_8888,
ColorSpace.sRGB,
SurfaceProps(pixelGeometry = PixelGeometry.UNKNOWN)
)
// Perform timestep and record all draw commands into [Picture]
val picture = trace("MetalRedrawer:draw:pictureRecording") {
pictureRecorder.beginRecording(
left = 0f,
top = 0f,
width.toFloat(),
height.toFloat()
).also { canvas ->
render(canvas, lastRenderTimestamp)
}

if (surface == null) {
// TODO: anomaly, log
// Logger.warn { "'Surface.makeFromBackendRenderTarget' returned null. Skipping the frame." }
picture.close()
renderTarget.close()
metalDrawablesHandler.releaseDrawable(metalDrawable)
return@autoreleasepool
}
pictureRecorder.finishRecordingAsPicture()
}

val interopTransaction = retrieveInteropTransaction()
if (!currentFrameRate.isNaN()) {
preferredFramesPerSecond = currentFrameRate.toLong()
currentFrameRate = Float.NaN
}

val presentsWithTransaction =
isForcedToPresentWithTransactionEveryFrame
|| interopTransaction.actions.isNotEmpty()
|| isInteropActive != interopTransaction.isInteropActive
metalLayer.presentsWithTransaction = presentsWithTransaction
val metalDrawable = trace("MetalRedrawer:draw:nextDrawable") {
metalDrawablesHandler.nextDrawable()
}

if (interopTransaction.isInteropActive) {
isInteropActive = true
}
if (metalDrawable == null) {
// TODO: anomaly, log
// Logger.warn { "'metalLayer.nextDrawable()' returned null. 'metalLayer.allowsNextDrawableTimeout' should be set to false. Skipping the frame." }
picture.close()
return@autoreleasepool
}

val mustEncodeAndPresentOnMainThread = presentsWithTransaction || waitUntilCompletion || !useSeparateRenderThreadWhenPossible
val renderTarget = BackendRenderTarget.makeMetal(
width,
height,
texturePtr = metalDrawablesHandler.drawableTexture(metalDrawable).rawValue
)

val surface = Surface.makeFromBackendRenderTarget(
context,
renderTarget,
SurfaceOrigin.TOP_LEFT,
SurfaceColorFormat.BGRA_8888,
ColorSpace.sRGB,
SurfaceProps(pixelGeometry = PixelGeometry.UNKNOWN)
)

if (surface == null) {
// TODO: anomaly, log
// Logger.warn { "'Surface.makeFromBackendRenderTarget' returned null. Skipping the frame." }
picture.close()
renderTarget.close()
metalDrawablesHandler.releaseDrawable(metalDrawable)
return@autoreleasepool
}

val encodeAndPresentBlock = {
trace("MetalRedrawer:draw:encodeAndPresent") {
if (useSeparateRenderThreadWhenPossible) {
dispatch_semaphore_wait(drawCanvasSemaphore, DISPATCH_TIME_FOREVER)
}
val interopTransaction = retrieveInteropTransaction()

surface.canvas.drawPicture(picture)
picture.close()
surface.flushAndSubmit()
val presentsWithTransaction =
isForcedToPresentWithTransactionEveryFrame
|| interopTransaction.actions.isNotEmpty()
|| isInteropActive != interopTransaction.isInteropActive
metalLayer.presentsWithTransaction = presentsWithTransaction

surface.close()
renderTarget.close()
if (interopTransaction.isInteropActive) {
isInteropActive = true
}

if (useSeparateRenderThreadWhenPossible) {
dispatch_semaphore_signal(drawCanvasSemaphore)
}
val mustEncodeAndPresentOnMainThread =
presentsWithTransaction || waitUntilCompletion || !useSeparateRenderThreadWhenPossible

val commandBuffer = queue.commandBuffer()!!
commandBuffer.label = "Present"
val encodeAndPresentBlock = {
trace("MetalRedrawer:draw:encodeAndPresent") {
if (useSeparateRenderThreadWhenPossible) {
dispatch_semaphore_wait(drawCanvasSemaphore, DISPATCH_TIME_FOREVER)
}

if (!presentsWithTransaction) {
// scheduleDrawablePresentation consumes metalDrawable
// don't use metalDrawable after this call
metalDrawablesHandler.scheduleDrawablePresentation(metalDrawable, commandBuffer)
}
surface.canvas.drawPicture(picture)
picture.close()
surface.flushAndSubmit()

dispatch_group_enter(inflightCommandBuffersGroup)
commandBuffer.addCompletedHandler {
dispatch_group_leave(inflightCommandBuffersGroup)
}
commandBuffer.commit()
surface.close()
renderTarget.close()

if (presentsWithTransaction) {
// If there are pending changes in UIKit interop, [waitUntilScheduled](https://developer.apple.com/documentation/metal/mtlcommandbuffer/1443036-waituntilscheduled) is called
// to ensure that transaction is available
trace("MetalRedrawer:draw:waitTransaction") {
commandBuffer.waitUntilScheduled()
if (useSeparateRenderThreadWhenPossible) {
dispatch_semaphore_signal(drawCanvasSemaphore)
}

// presentDrawable consumes metalDrawable
// don't use metalDrawable after this call
metalDrawablesHandler.presentDrawable(metalDrawable)
val commandBuffer = queue.commandBuffer()!!
commandBuffer.label = "Present"

interopTransaction.actions.fastForEach {
it.invoke()
if (!presentsWithTransaction) {
// scheduleDrawablePresentation consumes metalDrawable
// don't use metalDrawable after this call
metalDrawablesHandler.scheduleDrawablePresentation(
metalDrawable,
commandBuffer
)
}

if (interopTransaction.isInteropActive.not()) {
isInteropActive = false
dispatch_group_enter(inflightCommandBuffersGroup)
commandBuffer.addCompletedHandler {
dispatch_group_leave(inflightCommandBuffersGroup)
}
commandBuffer.commit()

if (presentsWithTransaction) {
// If there are pending changes in UIKit interop, [waitUntilScheduled](https://developer.apple.com/documentation/metal/mtlcommandbuffer/1443036-waituntilscheduled) is called
// to ensure that transaction is available
trace("MetalRedrawer:draw:waitTransaction") {
commandBuffer.waitUntilScheduled()
}

// presentDrawable consumes metalDrawable
// don't use metalDrawable after this call
metalDrawablesHandler.presentDrawable(metalDrawable)

interopTransaction.actions.fastForEach {
it.invoke()
}

if (interopTransaction.isInteropActive.not()) {
isInteropActive = false
}
}
}

if (waitUntilCompletion) {
trace("MetalRedrawer:draw:waitUntilCompleted") {
commandBuffer.waitUntilCompleted()
if (waitUntilCompletion) {
trace("MetalRedrawer:draw:waitUntilCompleted") {
commandBuffer.waitUntilCompleted()
}
}
}
}
}

if (mustEncodeAndPresentOnMainThread) {
encodeAndPresentBlock()
} else {
dispatch_async(renderingDispatchQueue) {
if (mustEncodeAndPresentOnMainThread) {
encodeAndPresentBlock()
} else {
dispatch_async(renderingDispatchQueue) {
encodeAndPresentBlock()
}
}
}
} finally {
isDrawRecursiveCall = false
}
}

Expand Down
4 changes: 2 additions & 2 deletions ...ui/src/uikitInstrumentedTest/kotlin/androidx/compose/ui/integrations/ComposeLaunchTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -86,7 +86,7 @@ class ComposeLaunchTest {

assertEquals(1, drawsCount, "Expected to draw only one frame on startup")

image.forEachPixel { _, _, color ->
image.forEachPixel(step = 4) { _, _, color ->
assertEquals(Color.Blue, color, "Expected to draw blue background")
}

Expand Down Expand Up @@ -123,7 +123,7 @@ class ComposeLaunchTest {

assertEquals(1, drawsCount, "Expected to draw only one frame on startup")

image.forEachPixel { _, _, color ->
image.forEachPixel(step = 4) { _, _, color ->
assertEquals(Color.Blue, color, "Expected to draw blue background")
}

Expand Down
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