Fix re-entrance in draw function

compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/scene/ComposeLayersViewController.ios.kt

@@ -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)

compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/window/ComposeContainerView.ios.kt

@@ -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

compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/window/MetalRedrawer.ios.kt

@@ -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
 
@@ -319,6 +321,10 @@ 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)
 
@@ -328,6 +334,7 @@ internal class MetalRedrawer(
             }
 
             if (width <= 0 || height <= 0) {
+                isDrawRecursiveCall = false
                 return@autoreleasepool
             }
 
@@ -358,6 +365,7 @@ internal class MetalRedrawer(
                 // TODO: anomaly, log
                 // Logger.warn { "'metalLayer.nextDrawable()' returned null. 'metalLayer.allowsNextDrawableTimeout' should be set to false. Skipping the frame." }
                 picture.close()
+                isDrawRecursiveCall = false
                 return@autoreleasepool
             }
 
@@ -382,6 +390,7 @@ internal class MetalRedrawer(
                 picture.close()
                 renderTarget.close()
                 metalDrawablesHandler.releaseDrawable(metalDrawable)
+                isDrawRecursiveCall = false
                 return@autoreleasepool
             }
 
@@ -467,6 +476,7 @@ internal class MetalRedrawer(
                 }
             }
         }
+        isDrawRecursiveCall = false
     }
 
     companion object {

compose/ui/ui/src/uikitInstrumentedTest/kotlin/androidx/compose/ui/integrations/ComposeLaunchTest.kt

@@ -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")
         }
 
@@ -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")
         }
 

compose/ui/ui/src/uikitInstrumentedTest/kotlin/androidx/compose/ui/layers/LayersRenderingTest.kt

@@ -0,0 +1,106 @@
+/*
+ * 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.layers
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.background
+import androidx.compose.ui.draw.drawBehind
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.test.captureScreenshot
+import androidx.compose.ui.test.runUIKitInstrumentedTest
+import androidx.compose.ui.test.utils.forEachPixel
+import androidx.compose.ui.window.Popup
+import androidx.compose.ui.window.PopupProperties
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import platform.UIKit.UIImage
+import platform.darwin.dispatch_async
+import platform.darwin.dispatch_get_main_queue
+
+class LayersRenderingTest {
+    @Test
+    fun testLayerContentOnFirstRender() = runUIKitInstrumentedTest {
+        var showRed by mutableStateOf(false)
+        var showGreen by mutableStateOf(false)
+        var onRender = {}
+        var frameImage: UIImage? = null
+
+        fun prepareForCaptureNextFrame() {
+            frameImage = null
+            onRender = {
+                dispatch_async(dispatch_get_main_queue()) {
+                    frameImage = captureScreenshot()
+                }
+                onRender = {}
+            }
+        }
+
+        setContent {
+            Box(Modifier.fillMaxSize().background(Color.Blue).drawBehind {
+                onRender()
+            })
+            if (showRed) {
+                Popup(
+                    onDismissRequest = {},
+                    properties = PopupProperties(usePlatformInsets = false)
+                ) {
+                    Box(Modifier.fillMaxSize().background(Color.Red))
+                }
+            }
+            if (showGreen) {
+                Popup(
+                    onDismissRequest = {},
+                    properties = PopupProperties(usePlatformInsets = false)
+                ) {
+                    Box(Modifier.fillMaxSize().background(Color.Green))
+                }
+            }
+        }
+
+        fun assertNextFrameColor(expectedColor: Color) {
+            prepareForCaptureNextFrame()
+            waitForIdle()
+
+            assertNotNull(frameImage)
+            frameImage!!.forEachPixel(step = 4) { _, _, actualColor ->
+                assertEquals(
+                    expectedColor,
+                    actualColor,
+                    "Expected to draw $expectedColor background"
+                )
+            }
+        }
+
+        showRed = true
+        assertNextFrameColor(Color.Red)
+
+        showRed = false
+        assertNextFrameColor(Color.Blue)
+
+        showGreen = true
+        assertNextFrameColor(Color.Green)
+
+        showGreen = false
+        assertNextFrameColor(Color.Blue)
+    }
+}

compose/ui/ui/src/uikitInstrumentedTest/kotlin/androidx/compose/ui/test/UIKitInstrumentedTest.kt

@@ -54,13 +54,20 @@ import kotlin.time.TimeSource
 import kotlinx.cinterop.ExperimentalForeignApi
 import kotlinx.cinterop.useContents
 import kotlinx.coroutines.Dispatchers
+import platform.CoreGraphics.CGSizeMake
 import platform.Foundation.NSDate
 import platform.Foundation.NSRunLoop
 import platform.Foundation.dateWithTimeIntervalSinceNow
 import platform.Foundation.runUntilDate
 import platform.UIKit.UIApplication
 import platform.UIKit.UIApplicationDelegateProtocol
 import platform.UIKit.UIColor
+import platform.UIKit.UIGraphicsBeginImageContextWithOptions
+import platform.UIKit.UIGraphicsEndImageContext
+import platform.UIKit.UIGraphicsGetCurrentContext
+import platform.UIKit.UIGraphicsGetImageFromCurrentImageContext
+import platform.UIKit.UIGraphicsImageRenderer
+import platform.UIKit.UIImage
 import platform.UIKit.UIInterfaceOrientationLandscapeLeft
 import platform.UIKit.UIInterfaceOrientationLandscapeRight
 import platform.UIKit.UIInterfaceOrientationMask
@@ -554,3 +561,25 @@ internal fun ComposeHostingViewController.waitForIdle() {
 internal fun ComposeHostingView.waitForIdle() {
     UIKitInstrumentedTest.waitUntil { !this.hasInvalidations() }
 }
+
+@OptIn(ExperimentalForeignApi::class)
+internal fun UIKitInstrumentedTest.captureScreenshot(): UIImage? {
+    val scale = UIScreen.mainScreen.scale
+    val size = UIScreen.mainScreen.bounds.useContents { CGSizeMake(size.width, size.height) }
+
+    UIGraphicsBeginImageContextWithOptions(size, false, scale)
+    UIGraphicsGetCurrentContext() ?: return null
+
+    val scene = appDelegate.window()?.windowScene ?: return null
+    scene.windows.mapNotNull { it as? UIWindow }
+        .filter { !it.hidden && it.alpha > 0.0 }
+        .sortedBy { it.windowLevel }
+        .forEach { window ->
+            window.drawViewHierarchyInRect(window.bounds, afterScreenUpdates = true)
+        }
+
+    val screenshot = UIGraphicsGetImageFromCurrentImageContext()
+    UIGraphicsEndImageContext()
+
+    return screenshot
+}

compose/ui/ui/src/uikitInstrumentedTest/kotlin/androidx/compose/ui/test/utils/UIImage+Utils.kt

@@ -30,7 +30,7 @@ import platform.CoreGraphics.CGRectMake
 import platform.UIKit.UIImage
 
 @OptIn(ExperimentalForeignApi::class)
-internal fun UIImage.forEachPixel(onPixel: (x: Int, y: Int, color: Color) -> Unit) {
+internal fun UIImage.forEachPixel(step: Int = 1, onPixel: (x: Int, y: Int, color: Color) -> Unit) {
     val cgImage = this.CGImage
     val width = CGImageGetWidth(cgImage).toInt()
     val height = CGImageGetHeight(cgImage).toInt()
@@ -52,8 +52,8 @@ internal fun UIImage.forEachPixel(onPixel: (x: Int, y: Int, color: Color) -> Uni
 
         CGContextDrawImage(context, CGRectMake(0.0, 0.0, width.toDouble(), height.toDouble()), cgImage)
 
-        for (y in 0 until height) {
-            for (x in 0 until width) {
+        for (y in 0 until height step step) {
+            for (x in 0 until width step step) {
                 val offset = (y * bytesPerRow) + (x * bytesPerPixel)
                 val r = pinned.get()[offset].toUByte().toInt()
                 val g = pinned.get()[offset + 1].toUByte().toInt()