wip aha subcomposelayout is a workaround

Author: zach-klippenstein

compose-backstack/src/androidTest/java/com/zachklipp/compose/backstack/BackstackStateTest.kt

@@ -9,8 +9,10 @@ import androidx.compose.runtime.mutableStateListOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.saveable.Saver
 import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.saveable.rememberSaveableStateHolder
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.SubcomposeLayout
 import androidx.compose.ui.test.assertIsDisplayed
 import androidx.compose.ui.test.junit4.createComposeRule
 import androidx.compose.ui.test.onNodeWithText
@@ -24,17 +26,53 @@ class BackstackStateTest {
   @get:Rule
   val compose = createComposeRule()
 
-  @Composable private fun Screen(name: String) {
-    var counter by rememberSaveable(stateSaver = Saver(
-      save = {
-        println("OMG saving $it for $name")
-        it
-      },
-      restore = {
-        println("OMG restoring $it for $name")
-        it
+  @Test fun is_compose_broken() {
+    var index by mutableStateOf(0)
+    compose.setContent {
+      val holder = rememberSaveableStateHolder()
+      holder.SaveableStateProvider(index) {
+        SubcomposeLayout { constraints ->
+          val measurable = subcompose(Unit) {
+            var counter by rememberSaveable { mutableStateOf(0) }
+            BasicText("Counter $index: $counter", Modifier.clickable { counter++ })
+          }.single()
+
+          val placeable = measurable.measure(constraints)
+          layout(placeable.width, placeable.height) {
+            placeable.placeRelative(0, 0)
+          }
+        }
       }
-    )) {
+    }
+
+    // Initial state.
+    compose.onNodeWithText("Counter 0: 0").assertIsDisplayed()
+
+    // Increment counter and check that it's incremented.
+    compose.onNodeWithText("Counter", substring = true).performClick()
+    compose.onNodeWithText("Counter 0: 1").assertIsDisplayed()
+
+    // Change the index to reset the counter, but save the old value.
+    index = 1
+    compose.onNodeWithText("Counter 1: 0").assertIsDisplayed()
+
+    // Revert the index to restore the old counter value.
+    index = 0
+    compose.onNodeWithText("Counter 0: 1").assertIsDisplayed()
+  }
+
+  @Composable private fun Screen(name: String) {
+    var counter by rememberSaveable(
+      stateSaver = Saver(
+        save = {
+          println("OMG saving $it for $name")
+          it
+        },
+        restore = {
+          println("OMG restoring $it for $name")
+          it
+        }
+      )) {
       println("OMG initializing counter")
       mutableStateOf(0)
     }

sample/src/main/java/com/zachklipp/compose/backstack/sample/ComposeBackstackActivity.kt

@@ -3,21 +3,70 @@ package com.zachklipp.compose.backstack.sample
 import android.os.Bundle
 import androidx.activity.compose.setContent
 import androidx.appcompat.app.AppCompatActivity
-import com.zachklipp.compose.backstack.viewer.BackstackViewerApp
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.text.BasicText
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.key
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.saveable.rememberSaveableStateHolder
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.SubcomposeLayout
+import androidx.compose.ui.unit.dp
 
 class ComposeBackstackActivity : AppCompatActivity() {
   override fun onCreate(savedInstanceState: Bundle?) {
     super.onCreate(savedInstanceState)
     setContent {
-      BackstackViewerApp(
-          namedCustomTransitions = listOf("Fancy" to FancyTransition),
-          prefabBackstacks = listOf(
-              listOf("one"),
-              listOf("one", "two"),
-              listOf("one", "two", "three"),
-              listOf("two", "one")
-          )
-      )
+//      BackstackViewerApp(
+//          namedCustomTransitions = listOf("Fancy" to FancyTransition),
+//          prefabBackstacks = listOf(
+//              listOf("one"),
+//              listOf("one", "two"),
+//              listOf("one", "two", "three"),
+//              listOf("two", "one")
+//          )
+//      )
+
+      var index by remember { mutableStateOf(0) }
+      val holder = rememberSaveableStateHolder()
+
+      Column {
+        BasicText("Index: $index")
+        BasicText("index++",
+          Modifier
+            .clickable { index++ }
+            .padding(16.dp))
+        BasicText("index--",
+          Modifier
+            .clickable { index-- }
+            .padding(16.dp))
+        Spacer(Modifier.height(24.dp))
+
+        holder.SaveableStateProvider(index) {
+          SubcomposeLayout { constraints ->
+            val measurable = subcompose(Unit) {
+              var counter by rememberSaveable { mutableStateOf(0) }
+              BasicText("Counter $index: $counter",
+                Modifier
+                  .clickable { counter++ }
+                  .padding(16.dp))
+            }.single()
+
+            val placeable = measurable.measure(constraints)
+            layout(placeable.width, placeable.height) {
+              placeable.placeRelative(0, 0)
+            }
+          }
+        }
+      }
     }
   }
 }