Fix animation frozen after app went background

compose/mpp/demo/src/uikitMain/kotlin/androidx/compose/mpp/demo/bugs/AnimationFreezeBug.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2024 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.mpp.demo.bugs
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material.Switch
+import androidx.compose.mpp.demo.Screen
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import platform.UIKit.UIApplication
+import platform.Foundation.NSURL
+
+val AnimationFreezeBug = Screen.Example("AnimationFreezeBug") {
+    Column(modifier = Modifier.fillMaxSize()) {
+        var state by remember { mutableStateOf(true) }
+        Switch(checked = state, onCheckedChange = {
+            state = it
+            UIApplication.sharedApplication.openURL(NSURL.URLWithString("app-settings:")!!)
+        })
+    }
+}

compose/mpp/demo/src/uikitMain/kotlin/androidx/compose/mpp/demo/bugs/IosBugs.kt

@@ -35,5 +35,6 @@ val IosBugs = Screen.Selection(
     KeyboardIMEActionPopup,
     ProperContainmentDisposal,
     ComposeAndNativeScroll,
-    MeasureAndLayoutCrash
+    MeasureAndLayoutCrash,
+    AnimationFreezeBug,
 )

compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/scene/ComposeSceneMediator.uikit.kt

@@ -68,6 +68,7 @@ import androidx.compose.ui.unit.roundToIntRect
 import androidx.compose.ui.unit.toDpRect
 import androidx.compose.ui.unit.toOffset
 import androidx.compose.ui.window.ComposeSceneKeyboardOffsetManager
+import androidx.compose.ui.window.ApplicationStateListener
 import androidx.compose.ui.window.FocusStack
 import androidx.compose.ui.window.InteractionUIView
 import androidx.compose.ui.window.KeyboardEventHandler
@@ -253,6 +254,15 @@ internal class ComposeSceneMediator(
         renderingUIViewFactory(interopContext, renderDelegate)
     }
 
+    private val applicationStateListener = ApplicationStateListener { isForeground ->
+        // Sometimes the application can trigger animation and go background before the animation is
+        // finished. The scheduled GPU work is performed, but no presentation can be done, causing
+        // mismatch between visual state and application state. This can be fixed by forcing
+        // a redraw when app returns to foreground, which will ensure that the visual state is in
+        // sync with the application state even if such sequence of events took a place.
+        renderingView.needRedraw()
+    }
+
     /**
      * view, that contains [interopViewContainer] and [interactionView] and is added to [container]
      */
@@ -490,6 +500,7 @@ internal class ComposeSceneMediator(
 
     fun dispose() {
         uiKitTextInputService.stopInput()
+        applicationStateListener.dispose()
         focusStack?.popUntilNext(renderingView)
         keyboardManager.stop()
         renderingView.dispose()
@@ -501,7 +512,7 @@ internal class ComposeSceneMediator(
         interopContext.retrieve().actions.forEach { it.invoke() }
     }
 
-    fun onComposeSceneInvalidate() = renderingView.needRedraw()
+    private fun onComposeSceneInvalidate() = renderingView.needRedraw()
 
     fun setLayout(value: SceneLayout) {
         _layout = value