Read render diagnostics

Required dependencies

This page is standalone. Host diagnostics and RenderStats are in the base application modules; no optional diagnostics artifact is required:

build.gradle.kts

repositories { mavenCentral() }

dependencies {
    implementation("com.viewcompose:viewcompose-material3-android:0.1.0-alpha01")
    implementation("androidx.activity:activity:1.12.4")
    implementation("com.google.android.material:material:1.13.0")
}

Sample renderer counters on demand

Create RenderDiagnosticsTutorialActivity.kt:

package com.viewcompose.samples.tutorials

import android.os.Bundle
import androidx.activity.ComponentActivity
import com.viewcompose.material3.android.setMaterial3UiContent
import com.viewcompose.runtime.mutableStateOf
import com.viewcompose.ui.modifier.Modifier
import com.viewcompose.ui.modifier.fillMaxSize
import com.viewcompose.ui.modifier.padding
import com.viewcompose.ui.unit.dp
import com.viewcompose.ui.foundation.Button
import com.viewcompose.ui.foundation.Column
import com.viewcompose.ui.foundation.RenderDiagnosticCollection
import com.viewcompose.ui.foundation.RenderDiagnostics
import com.viewcompose.ui.foundation.RenderFrameCompleted
import com.viewcompose.ui.foundation.RenderFrameDiagnosticLevel
import com.viewcompose.ui.foundation.RenderStats
import com.viewcompose.ui.foundation.Text
import com.viewcompose.ui.foundation.remember
import java.util.concurrent.atomic.AtomicReference

class RenderDiagnosticsTutorialActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val latestStats = AtomicReference(RenderStats())
        val diagnostics = RenderDiagnostics(
            collection = RenderDiagnosticCollection(
                lifecycle = false,
                failures = false,
                frameLevel = RenderFrameDiagnosticLevel.Stats,
            ),
            sink = { event ->
                if (event is RenderFrameCompleted) {
                    event.stats?.let(latestStats::set)
                }
            },
        )
        setMaterial3UiContent(
            debug = true,
            debugTag = "RenderTutorial",
            diagnostics = diagnostics,
        ) {
            val summary = remember { mutableStateOf("No sample yet") }

            Column(
                spacing = 12.dp,
                modifier = Modifier.fillMaxSize().padding(24.dp),
            ) {
                Button(
                    "Sample render stats",
                    onClick = {
                        val stats = latestStats.get()
                        summary.value =
                            "${stats.inserts} inserts, ${stats.reuses} reuses, " +
                                "${stats.patchedNodes} patches"
                    },
                )
                Text(summary.value)
            }
        }
    }
}

The diagnostics sink runs synchronously after authoritative frames. Store the immutable stats snapshot outside composition and read it only from an explicit UI event. Writing every RenderFrameCompleted event directly into observed UI state would create a render-observe-render loop and distort the counters being measured.

Count production failures without frame trees

Add the optional artifact when the application needs bounded recurring-failure counts:

build.gradle.kts

dependencies {
    implementation("com.viewcompose:viewcompose-diagnostics:0.1.0-alpha01")
}

Use one application-owned aggregator as a failure-only sink:

fun boundedFailureAggregationSample(
    install: (RenderDiagnostics) -> Unit,
): BoundedRenderFailureAggregator {
    val aggregator = BoundedRenderFailureAggregator()
    val diagnostics = RenderDiagnostics(
        collection = RenderDiagnosticCollection(
            lifecycle = false,
            failures = true,
            frameLevel = RenderFrameDiagnosticLevel.None,
        ),
        sink = aggregator,
    )
    install(diagnostics)
    return aggregator
}

Schedule snapshot/export outside sink delivery. The snapshot contains only bounded redacted fingerprints and safe framework context; it contains no original Throwable, message, raw node key, application stack, file, or line. The framework does not choose a scheduler, storage system, consent model, upload endpoint, or telemetry vendor.

Inspect the same app from Android Studio

Add debugImplementation("com.viewcompose:viewcompose-preview:0.1.0-alpha04"), run the debuggable app, and choose Inspect Device Diagnostics in Android Studio. Select the Host Session once. Its summary keeps the latest committed frame separate from a later rolled-back attempt and shows only a safe failure phase, recovery, exception type, and optional Android View operation.

Use Session sources to return to this Activity, Mounted nodes to load and optionally highlight a real View boundary, and Finite timing only while reproducing a bounded interaction. Click Refresh snapshot after another render; the inspector never polls or records a continuous history. If you need a deterministic timing target, the Demo Diagnostics → Renderer route exposes a visible 0/8 to 8/8 workload.

Verify the result

Press Sample render stats and confirm that a stable counter summary appears. If the optional Preview artifact is present, also confirm the inspector shows the selected Session, source, and latest committed frame without changing the running page. Debug diagnostics can add work, so use release benchmarks for performance conclusions. Compile with:

./gradlew :samples:tutorials:assembleDebug

See the Diagnostics guide and Diagnostics module manual for failure hooks, redaction, render traces, and logging policy.