[Jetchat] Fix conversation scroll jank and add Macrobenchmarks

Jetchat/.gitignore

@@ -14,3 +14,6 @@
 .cxx
 local.properties
 .kotlin/
+
+# Macrobenchmark results and Perfetto traces from local performance runs
+/benchmark_reports

Jetchat/app/build.gradle.kts

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 plugins {
     alias(libs.plugins.android.application)
     alias(libs.plugins.compose)
+    alias(libs.plugins.androidx.baselineprofile)
 }
 
 android {
@@ -63,6 +64,13 @@ android {
                 "proguard-rules.pro",
             )
         }
+
+        // Non-debuggable, non-minified build type for Macrobenchmark and composition tracing
+        create("benchmark") {
+            initWith(getByName("debug"))
+            isDebuggable = false
+            signingConfig = signingConfigs.getByName("debug")
+        }
     }
 
     kotlin {
@@ -88,6 +96,11 @@ android {
     }
 }
 
+baselineProfile {
+    // Put the generated profile in src/main so every build type, including benchmark, ships it
+    mergeIntoMain = true
+}
+
 dependencies {
     val composeBom = platform(libs.androidx.compose.bom)
     implementation(composeBom)
@@ -115,8 +128,13 @@ dependencies {
     implementation(libs.androidx.compose.ui.util)
     implementation(libs.androidx.compose.ui.viewbinding)
     implementation(libs.androidx.compose.ui.googlefonts)
+    // Adds composable function names to Perfetto traces
+    implementation(libs.androidx.compose.runtime.tracing)
+    implementation(libs.androidx.profileinstaller)
+    baselineProfile(project(":benchmark"))
 
     implementation(libs.androidx.media3.exoplayer)
+    implementation(libs.coil.kt.compose)
     implementation(libs.androidx.media3.ui.compose)
 
     debugImplementation(libs.androidx.compose.ui.test.manifest)

Jetchat/app/src/benchmark/AndroidManifest.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright 2026 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
+  ~
+  ~     https://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.
+  -->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <!-- Required for macrobenchmark to write trace files on some API levels -->
+    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
+    <application>
+        <profileable android:shell="true" />
+    </application>
+</manifest>

Jetchat/app/src/main/java/com/example/compose/jetchat/components/JetchatDrawer.kt

@@ -55,6 +55,7 @@ import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
+import coil.compose.AsyncImage
 import com.example.compose.jetchat.R
 import com.example.compose.jetchat.data.colleagueProfile
 import com.example.compose.jetchat.data.meProfile
@@ -191,8 +192,9 @@ private fun ProfileItem(text: String, @DrawableRes profilePic: Int?, selected: B
             .padding(start = 16.dp, top = 16.dp, bottom = 16.dp)
             .size(24.dp)
         if (profilePic != null) {
-            Image(
-                painter = painterResource(id = profilePic),
+            // Profile photos are large rasters shown at 24dp: decode off the main thread at that size
+            AsyncImage(
+                model = profilePic,
                 modifier = paddingSizeModifier.then(Modifier.clip(CircleShape)),
                 contentScale = ContentScale.Crop,
                 contentDescription = null,

Jetchat/app/src/main/java/com/example/compose/jetchat/conversation/Conversation.kt

@@ -121,6 +121,7 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
+import coil.compose.AsyncImage
 import com.example.compose.jetchat.FunctionalityNotAvailablePopup
 import com.example.compose.jetchat.R
 import com.example.compose.jetchat.blur.backdropBlur
@@ -785,13 +786,9 @@ fun ChatItemBubble(
             if (hasText) {
                 Spacer(modifier = Modifier.height(4.dp))
             }
-            val painter = painterResource(imageRes)
-            val intrinsicSize = painter.intrinsicSize
-            val aspectRatio = if (intrinsicSize.width > 0f && intrinsicSize.height > 0f) {
-                intrinsicSize.width / intrinsicSize.height
-            } else {
-                1f
-            }
+            // Message images are large photos: decode them off the main thread at display size
+            // instead of with painterResource, which decodes the full bitmap during composition.
+            val aspectRatio = rememberImageAspectRatio(imageRes)
             Surface(
                 color = if (isLiked) Color.Transparent else backgroundBubbleColor,
                 shape = bubbleShape,
@@ -814,8 +811,8 @@ fun ChatItemBubble(
                             },
                         ),
                 ) {
-                    Image(
-                        painter = painter,
+                    AsyncImage(
+                        model = imageRes,
                         contentScale = ContentScale.Crop,
                         modifier = Modifier
                             .padding(if (isLiked) 8.dp else 0.dp)

Jetchat/app/src/main/java/com/example/compose/jetchat/conversation/ImageAspectRatio.kt

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2026 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
+ *
+ *     https://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 com.example.compose.jetchat.conversation
+
+import android.content.res.Resources
+import android.graphics.BitmapFactory
+import androidx.annotation.DrawableRes
+import androidx.collection.mutableIntFloatMapOf
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.platform.LocalResources
+
+private val aspectRatioCache = mutableIntFloatMapOf()
+
+/**
+ * Width / height of a raster drawable, read from the image header only. Lets message bubbles size
+ * themselves before the image is decoded asynchronously, so the layout matches a synchronous load.
+ */
+@Composable
+fun rememberImageAspectRatio(@DrawableRes imageRes: Int): Float {
+    val resources = LocalResources.current
+    return remember(imageRes, resources) {
+        aspectRatioCache.getOrPut(imageRes) { readAspectRatio(resources, imageRes) }
+    }
+}
+
+private fun readAspectRatio(resources: Resources, @DrawableRes imageRes: Int): Float {
+    val options = BitmapFactory.Options().apply { inJustDecodeBounds = true }
+    BitmapFactory.decodeResource(resources, imageRes, options)
+    return if (options.outWidth > 0 && options.outHeight > 0) {
+        options.outWidth.toFloat() / options.outHeight
+    } else {
+        1f
+    }
+}

Jetchat/benchmark/build.gradle.kts

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2026 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
+ *
+ *     https://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.
+ */
+
+
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+
+plugins {
+    alias(libs.plugins.android.test)
+    alias(libs.plugins.androidx.baselineprofile)
+}
+
+android {
+    namespace = "com.example.compose.jetchat.benchmark"
+    compileSdk = libs.versions.compileSdk.get().toInt()
+    compileSdkMinor = 2
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    kotlin {
+        compilerOptions {
+            jvmTarget = JvmTarget.fromTarget("17")
+        }
+    }
+
+    defaultConfig {
+        minSdk = 28
+        targetSdk = libs.versions.targetSdk.get().toInt()
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    targetProjectPath = ":app"
+    // Enable the benchmark to run separately from the app process
+    experimentalProperties["android.experimental.self-instrumenting"] = true
+
+    buildTypes {
+        create("benchmark") {
+            isMinifyEnabled = false
+            signingConfig = signingConfigs.getByName("debug")
+            // Target the app's non-debuggable, non-minified benchmark build type
+            matchingFallbacks += listOf("benchmark", "release")
+        }
+    }
+}
+
+dependencies {
+    implementation(libs.androidx.test.ext.junit)
+    implementation(libs.androidx.test.uiautomator)
+    implementation(libs.androidx.benchmark.macro.junit4)
+}

Jetchat/benchmark/src/main/java/com/example/compose/jetchat/benchmark/BaselineProfileGenerator.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2026 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
+ *
+ *     https://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 com.example.compose.jetchat.benchmark
+
+import androidx.benchmark.macro.junit4.BaselineProfileRule
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class BaselineProfileGenerator {
+    @get:Rule
+    val baselineProfileRule = BaselineProfileRule()
+
+    @Test
+    fun generate() = baselineProfileRule.collect(packageName = TARGET_PACKAGE) {
+        pressHome()
+        launchJetchat()
+        val list = waitForConversation()
+        scrollConversation(list)
+    }
+}

Jetchat/benchmark/src/main/java/com/example/compose/jetchat/benchmark/ConversationScrollBenchmark.kt

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2026 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
+ *
+ *     https://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 com.example.compose.jetchat.benchmark
+
+import androidx.benchmark.macro.CompilationMode
+import androidx.benchmark.macro.ExperimentalMetricApi
+import androidx.benchmark.macro.FrameTimingMetric
+import androidx.benchmark.macro.StartupMode
+import androidx.benchmark.macro.TraceSectionMetric
+import androidx.benchmark.macro.junit4.MacrobenchmarkRule
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@OptIn(ExperimentalMetricApi::class)
+@RunWith(AndroidJUnit4::class)
+class ConversationScrollBenchmark {
+    @get:Rule
+    val benchmarkRule = MacrobenchmarkRule()
+
+    @Test
+    fun scrollConversationNone() = scroll(CompilationMode.None())
+
+    @Test
+    fun scrollConversationPartial() = scroll(CompilationMode.Partial())
+
+    private fun scroll(compilationMode: CompilationMode) = benchmarkRule.measureRepeated(
+        packageName = TARGET_PACKAGE,
+        metrics = listOf(
+            FrameTimingMetric(),
+            // Mode.Sum reports both Compose:recomposeSumMs and Compose:recomposeCount
+            TraceSectionMetric("Compose:recompose", TraceSectionMetric.Mode.Sum),
+        ),
+        compilationMode = compilationMode,
+        startupMode = StartupMode.WARM,
+        iterations = 10,
+        setupBlock = {
+            pressHome()
+            launchJetchat()
+        },
+    ) {
+        val list = waitForConversation()
+        scrollConversation(list)
+    }
+}