Add new APNG renderer, just for internal users for now.

app/build.gradle.kts

@@ -613,6 +613,7 @@ dependencies {
   implementation(project(":core:models-jvm"))
   implementation(project(":feature:camera"))
   implementation(project(":feature:registration"))
+  implementation(project(":lib:apng"))
 
   implementation(libs.androidx.fragment.ktx)
   implementation(libs.androidx.appcompat) {

app/src/main/java/org/thoughtcrime/securesms/components/settings/app/labs/LabsSettingsEvents.kt

@@ -12,4 +12,5 @@ sealed interface LabsSettingsEvents {
   data class ToggleGroupSuggestionsForMembers(val enabled: Boolean) : LabsSettingsEvents
   data class ToggleBetterSearch(val enabled: Boolean) : LabsSettingsEvents
   data class ToggleAutoLowerHand(val enabled: Boolean) : LabsSettingsEvents
+  data class ToggleNewApngRenderer(val enabled: Boolean) : LabsSettingsEvents
 }

app/src/main/java/org/thoughtcrime/securesms/components/settings/app/labs/LabsSettingsFragment.kt

@@ -142,6 +142,15 @@ private fun LabsSettingsContent(
           onCheckChanged = { onEvent(LabsSettingsEvents.ToggleAutoLowerHand(it)) }
         )
       }
+
+      item {
+        Rows.ToggleRow(
+          checked = state.newApngRenderer,
+          text = "New APNG Renderer",
+          label = "Use the new custom APNG renderer instead of the existing third-party library. Requires an app restart to take effect.",
+          onCheckChanged = { onEvent(LabsSettingsEvents.ToggleNewApngRenderer(it)) }
+        )
+      }
     }
   }
 }

app/src/main/java/org/thoughtcrime/securesms/components/settings/app/labs/LabsSettingsState.kt

@@ -14,5 +14,6 @@ data class LabsSettingsState(
   val incognito: Boolean = false,
   val groupSuggestionsForMembers: Boolean = false,
   val betterSearch: Boolean = false,
-  val autoLowerHand: Boolean = false
+  val autoLowerHand: Boolean = false,
+  val newApngRenderer: Boolean = false
 )

app/src/main/java/org/thoughtcrime/securesms/components/settings/app/labs/LabsSettingsViewModel.kt

@@ -41,6 +41,10 @@ class LabsSettingsViewModel : ViewModel() {
         SignalStore.labs.autoLowerHand = event.enabled
         _state.value = _state.value.copy(autoLowerHand = event.enabled)
       }
+      is LabsSettingsEvents.ToggleNewApngRenderer -> {
+        SignalStore.labs.newApngRenderer = event.enabled
+        _state.value = _state.value.copy(newApngRenderer = event.enabled)
+      }
     }
   }
 
@@ -51,7 +55,8 @@ class LabsSettingsViewModel : ViewModel() {
       incognito = SignalStore.labs.incognito,
       groupSuggestionsForMembers = SignalStore.labs.groupSuggestionsForMembers,
       betterSearch = SignalStore.labs.betterSearch,
-      autoLowerHand = SignalStore.labs.autoLowerHand
+      autoLowerHand = SignalStore.labs.autoLowerHand,
+      newApngRenderer = SignalStore.labs.newApngRenderer
     )
   }
 }

app/src/main/java/org/thoughtcrime/securesms/glide/SignalGlideComponents.java

@@ -16,11 +16,12 @@ import com.bumptech.glide.load.resource.gif.ByteBufferGifDecoder;
 import com.bumptech.glide.load.resource.gif.GifDrawable;
 import com.bumptech.glide.load.resource.gif.StreamGifDecoder;
 
+import org.signal.apng.ApngDecoder;
 import org.signal.blurhash.BlurHash;
+import org.signal.glide.load.resource.apng.decode.APNGDecoder;
 import org.signal.glide.blurhash.BlurHashModelLoader;
 import org.signal.glide.blurhash.BlurHashResourceDecoder;
 import org.signal.glide.common.io.InputStreamFactory;
-import org.signal.glide.load.resource.apng.decode.APNGDecoder;
 import org.thoughtcrime.securesms.badges.load.BadgeLoader;
 import org.thoughtcrime.securesms.badges.load.GiftBadgeModel;
 import org.thoughtcrime.securesms.badges.models.Badge;
@@ -29,9 +30,13 @@ import org.thoughtcrime.securesms.contacts.avatars.ContactPhotoLoader;
 import org.thoughtcrime.securesms.crypto.AttachmentSecret;
 import org.thoughtcrime.securesms.crypto.AttachmentSecretProvider;
 import org.thoughtcrime.securesms.giph.model.ChunkedImageUrl;
+import org.thoughtcrime.securesms.glide.cache.ApngDrawableTranscoder;
 import org.thoughtcrime.securesms.glide.cache.ApngFrameDrawableTranscoder;
+import org.thoughtcrime.securesms.glide.cache.ApngInputStreamFactoryResourceDecoder;
+import org.thoughtcrime.securesms.glide.cache.ApngInputStreamResourceDecoder;
 import org.thoughtcrime.securesms.glide.cache.ByteBufferApngDecoder;
 import org.thoughtcrime.securesms.glide.cache.EncryptedApngCacheEncoder;
+import org.thoughtcrime.securesms.glide.cache.EncryptedApngResourceEncoder;
 import org.thoughtcrime.securesms.glide.cache.EncryptedBitmapResourceEncoder;
 import org.thoughtcrime.securesms.glide.cache.EncryptedCacheDecoder;
 import org.thoughtcrime.securesms.glide.cache.EncryptedCacheEncoder;
@@ -46,6 +51,7 @@ import org.signal.glide.decryptableuri.DecryptableUri;
 import org.signal.glide.decryptableuri.DecryptableUriStreamLoader;
 import org.thoughtcrime.securesms.mms.RegisterGlideComponents;
 import org.thoughtcrime.securesms.mms.SignalGlideModule;
+import org.thoughtcrime.securesms.keyvalue.SignalStore;
 import org.thoughtcrime.securesms.stickers.StickerRemoteUri;
 import org.thoughtcrime.securesms.stickers.StickerRemoteUriLoader;
 import org.thoughtcrime.securesms.stories.StoryTextPostModel;
@@ -85,16 +91,25 @@ public class SignalGlideComponents implements RegisterGlideComponents {
     registry.prepend(Bitmap.class, new EncryptedBitmapResourceEncoder(secret));
     registry.prepend(BitmapDrawable.class, new BitmapDrawableEncoder(glide.getBitmapPool(), encryptedBitmapResourceEncoder));
 
-    ByteBufferApngDecoder    byteBufferApngDecoder    = new ByteBufferApngDecoder();
-    StreamApngDecoder        streamApngDecoder        = new StreamApngDecoder(byteBufferApngDecoder);
-    StreamFactoryApngDecoder streamFactoryApngDecoder = new StreamFactoryApngDecoder(byteBufferApngDecoder, glide, registry);
 
-    registry.prepend(InputStream.class, APNGDecoder.class, streamApngDecoder);
-    registry.prepend(InputStreamFactory.class, APNGDecoder.class, streamFactoryApngDecoder);
-    registry.prepend(ByteBuffer.class, APNGDecoder.class, byteBufferApngDecoder);
-    registry.prepend(APNGDecoder.class, new EncryptedApngCacheEncoder(secret));
-    registry.prepend(File.class, APNGDecoder.class, new EncryptedCacheDecoder<>(secret, streamApngDecoder));
-    registry.register(APNGDecoder.class, Drawable.class, new ApngFrameDrawableTranscoder());
+    if (SignalStore.labs().getNewApngRenderer()) {
+      registry.prepend(InputStream.class, ApngDecoder.class, new ApngInputStreamResourceDecoder());
+      registry.prepend(InputStreamFactory.class, ApngDecoder.class, new ApngInputStreamFactoryResourceDecoder());
+      registry.prepend(ApngDecoder.class, new EncryptedApngResourceEncoder(secret));
+      registry.prepend(File.class, ApngDecoder.class, new EncryptedCacheDecoder<>(secret, new ApngInputStreamResourceDecoder()));
+      registry.register(ApngDecoder.class, Drawable.class, new ApngDrawableTranscoder());
+    } else {
+      ByteBufferApngDecoder    byteBufferApngDecoder    = new ByteBufferApngDecoder();
+      StreamApngDecoder        streamApngDecoder        = new StreamApngDecoder(byteBufferApngDecoder);
+      StreamFactoryApngDecoder streamFactoryApngDecoder = new StreamFactoryApngDecoder(byteBufferApngDecoder, glide, registry);
+
+      registry.prepend(InputStream.class, APNGDecoder.class, streamApngDecoder);
+      registry.prepend(InputStreamFactory.class, APNGDecoder.class, streamFactoryApngDecoder);
+      registry.prepend(ByteBuffer.class, APNGDecoder.class, byteBufferApngDecoder);
+      registry.prepend(APNGDecoder.class, new EncryptedApngCacheEncoder(secret));
+      registry.prepend(File.class, APNGDecoder.class, new EncryptedCacheDecoder<>(secret, streamApngDecoder));
+      registry.register(APNGDecoder.class, Drawable.class, new ApngFrameDrawableTranscoder());
+    }
 
     registry.prepend(BlurHash.class, Bitmap.class, new BlurHashResourceDecoder());
     registry.prepend(StoryTextPostModel.class, Bitmap.class, new StoryTextPostModel.Decoder());

app/src/main/java/org/thoughtcrime/securesms/glide/cache/ApngDrawableTranscoder.kt

@@ -0,0 +1,28 @@
+package org.thoughtcrime.securesms.glide.cache
+
+import android.graphics.drawable.Drawable
+import com.bumptech.glide.load.Options
+import com.bumptech.glide.load.engine.Resource
+import com.bumptech.glide.load.resource.drawable.DrawableResource
+import com.bumptech.glide.load.resource.transcode.ResourceTranscoder
+import org.signal.apng.ApngDecoder
+import org.signal.apng.ApngDrawable
+
+class ApngDrawableTranscoder : ResourceTranscoder<ApngDecoder, Drawable> {
+  override fun transcode(toTranscode: Resource<ApngDecoder>, options: Options): Resource<Drawable> {
+    val decoder = toTranscode.get()
+    val drawable = ApngDrawable(decoder).apply {
+      loopForever = true
+    }
+
+    return object : DrawableResource<Drawable>(drawable) {
+      override fun getResourceClass(): Class<Drawable> = Drawable::class.java
+
+      override fun getSize(): Int = 0
+
+      override fun recycle() {
+        (get() as ApngDrawable).recycle()
+      }
+    }
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/glide/cache/ApngInputStreamFactoryResourceDecoder.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.glide.cache
+
+import com.bumptech.glide.load.Options
+import com.bumptech.glide.load.ResourceDecoder
+import com.bumptech.glide.load.engine.Resource
+import org.signal.apng.ApngDecoder
+import org.signal.core.util.readFully
+import org.signal.glide.apng.ApngOptions
+import org.signal.glide.common.io.InputStreamFactory
+import java.io.ByteArrayInputStream
+import java.io.IOException
+
+class ApngInputStreamFactoryResourceDecoder : ResourceDecoder<InputStreamFactory, ApngDecoder> {
+
+  override fun handles(source: InputStreamFactory, options: Options): Boolean {
+    return if (options.get(ApngOptions.ANIMATE) == true) {
+      ApngDecoder.isApng(source.create())
+    } else {
+      false
+    }
+  }
+
+  @Throws(IOException::class)
+  override fun decode(source: InputStreamFactory, width: Int, height: Int, options: Options): Resource<ApngDecoder>? {
+    val data: ByteArray = source.create().readFully()
+    val decoder = ApngDecoder(ByteArrayInputStream(data))
+    return ApngResource(decoder, data.size)
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/glide/cache/ApngInputStreamResourceDecoder.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.glide.cache
+
+import com.bumptech.glide.load.Options
+import com.bumptech.glide.load.ResourceDecoder
+import com.bumptech.glide.load.engine.Resource
+import org.signal.apng.ApngDecoder
+import org.signal.core.util.readFully
+import org.signal.core.util.stream.LimitedInputStream
+import org.signal.glide.apng.ApngOptions
+import java.io.ByteArrayInputStream
+import java.io.IOException
+import java.io.InputStream
+
+class ApngInputStreamResourceDecoder : ResourceDecoder<InputStream, ApngDecoder> {
+  companion object {
+    /** Set to match [com.bumptech.glide.load.data.InputStreamRewinder]'s read limit  */
+    private const val READ_LIMIT: Long = 5 * 1024 * 1024
+  }
+
+  override fun handles(source: InputStream, options: Options): Boolean {
+    return if (options.get(ApngOptions.ANIMATE)!!) {
+      ApngDecoder.isApng(LimitedInputStream(source, READ_LIMIT))
+    } else {
+      false
+    }
+  }
+
+  @Throws(IOException::class)
+  override fun decode(source: InputStream, width: Int, height: Int, options: Options): Resource<ApngDecoder>? {
+    val data: ByteArray = source.readFully()
+    val decoder = ApngDecoder(ByteArrayInputStream(data))
+    return ApngResource(decoder, data.size)
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/glide/cache/ApngResource.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.glide.cache
+
+import com.bumptech.glide.load.engine.Resource
+import org.signal.apng.ApngDecoder
+
+class ApngResource(private val decoder: ApngDecoder, private val size: Int) : Resource<ApngDecoder> {
+  override fun getResourceClass(): Class<ApngDecoder> = ApngDecoder::class.java
+
+  override fun get(): ApngDecoder = decoder
+
+  override fun getSize(): Int = size
+
+  override fun recycle() {
+    decoder.inputStream.close()
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/glide/cache/EncryptedApngResourceEncoder.kt

@@ -0,0 +1,36 @@
+package org.thoughtcrime.securesms.glide.cache
+
+import com.bumptech.glide.load.EncodeStrategy
+import com.bumptech.glide.load.Options
+import com.bumptech.glide.load.ResourceEncoder
+import com.bumptech.glide.load.engine.Resource
+import org.signal.apng.ApngDecoder
+import org.signal.core.util.logging.Log.tag
+import org.signal.core.util.logging.Log.w
+import java.io.File
+import java.io.IOException
+
+internal class EncryptedApngResourceEncoder(private val secret: ByteArray) : EncryptedCoder(), ResourceEncoder<ApngDecoder> {
+  override fun getEncodeStrategy(options: Options): EncodeStrategy {
+    return EncodeStrategy.SOURCE
+  }
+
+  override fun encode(data: Resource<ApngDecoder>, file: File, options: Options): Boolean {
+    try {
+      val input = data.get().inputStream
+      val output = createEncryptedOutputStream(secret, file)
+
+      input.reset()
+      input.copyTo(output)
+
+      return true
+    } catch (e: IOException) {
+      w(TAG, e)
+    }
+    return false
+  }
+
+  companion object {
+    private val TAG = tag(EncryptedApngResourceEncoder::class.java)
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/keyvalue/LabsValues.kt

@@ -10,6 +10,7 @@ class LabsValues internal constructor(store: KeyValueStore) : SignalStoreValues(
     const val GROUP_SUGGESTIONS_FOR_MEMBERS: String = "labs.group_suggestions_for_members"
     const val BETTER_SEARCH: String = "labs.better_search"
     const val AUTO_LOWER_HAND: String = "labs.auto_lower_hand"
+    const val NEW_APNG_RENDERER: String = "labs.new_apng_renderer"
   }
 
   public override fun onFirstEverAppLaunch() = Unit
@@ -28,6 +29,8 @@ class LabsValues internal constructor(store: KeyValueStore) : SignalStoreValues(
 
   var autoLowerHand by booleanValue(AUTO_LOWER_HAND, true).falseForExternalUsers()
 
+  var newApngRenderer by booleanValue(NEW_APNG_RENDERER, true).falseForExternalUsers()
+
   private fun SignalStoreValueDelegate<Boolean>.falseForExternalUsers(): SignalStoreValueDelegate<Boolean> {
     return this.map { actualValue -> RemoteConfig.internalUser && actualValue }
   }

app/src/main/java/org/thoughtcrime/securesms/util/DeviceProperties.java

@@ -12,6 +12,7 @@ import androidx.annotation.RequiresApi;
 
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.dependencies.AppDependencies;
+import org.thoughtcrime.securesms.keyvalue.SignalStore;
 
 /**
  * Easy access to various properties of the device, typically to make performance-related decisions.
@@ -25,6 +26,10 @@ public final class DeviceProperties {
    * large numbers of APNGs simultaneously.
    */
   public static boolean shouldAllowApngStickerAnimation(@NonNull Context context) {
+    if (SignalStore.labs().getNewApngRenderer()) {
+      return true;
+    }
+
     MemoryInfo memoryInfo = getMemoryInfo(context);
     int        memoryMb   = (int) ByteUnit.BYTES.toMegabytes(memoryInfo.totalMem);
 

core/util-jvm/src/main/java/org/signal/core/util/ByteArrayExtensions.kt

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.core.util
+
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
+
+fun ByteArray.toUInt(): UInt {
+  return ByteBuffer.wrap(this).order(ByteOrder.BIG_ENDIAN).int.toUInt()
+}
+
+fun ByteArray.toUShort(): UShort {
+  return ByteBuffer.wrap(this).order(ByteOrder.BIG_ENDIAN).getShort().toUShort()
+}

core/util-jvm/src/main/java/org/signal/core/util/InputStreamExtensions.kt

@@ -10,6 +10,7 @@ import java.io.ByteArrayOutputStream
 import java.io.IOException
 import java.io.InputStream
 import java.io.OutputStream
+import kotlin.jvm.Throws
 import kotlin.math.min
 
 /**
@@ -107,6 +108,13 @@ fun InputStream.readLength(): Long {
   return count
 }
 
+/**
+ * Reads a 32-bit unsigned integer from the stream.
+ */
+fun InputStream.readUInt(): UInt {
+  return this.readNBytesOrThrow(4).toUInt()
+}
+
 /**
  * Reads the contents of the stream and discards them.
  */

core/util-jvm/src/main/java/org/signal/core/util/OutputStreamExtensions.kt

@@ -6,6 +6,8 @@
 package org.signal.core.util
 
 import java.io.OutputStream
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
 
 /**
  * Writes a 32-bit variable-length integer to the stream.
@@ -30,3 +32,11 @@ fun OutputStream.writeVarInt32(value: Int) {
     }
   }
 }
+
+/**
+ * Writes a 32-bit unsigned integer to the stream.
+ */
+fun OutputStream.writeUInt(value: UInt) {
+  // Note that casting to an int here is fine, because at the end of the day, we're just writing 4 bytes to the stream
+  this.write(ByteBuffer.allocate(4).order(ByteOrder.BIG_ENDIAN).putInt(value.toInt()).array())
+}

core/util-jvm/src/main/java/org/signal/core/util/stream/Crc32OutputStream.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.core.util.stream
+
+import java.io.FilterOutputStream
+import java.io.OutputStream
+import java.util.zip.CRC32
+
+/**
+ * A simple pass-through stream that calculates a CRC32 as data is written to the target [OutputStream].
+ */
+class Crc32OutputStream(private val wrapped: OutputStream) : FilterOutputStream(wrapped) {
+  private val crc32 = CRC32()
+
+  val currentCrc32: Long
+    get() = crc32.value
+
+  override fun write(byte: Int) {
+    wrapped.write(byte)
+    crc32.update(byte)
+  }
+
+  override fun write(data: ByteArray) {
+    write(data, 0, data.size)
+  }
+
+  override fun write(data: ByteArray, offset: Int, length: Int) {
+    wrapped.write(data, offset, length)
+    crc32.update(data, offset, length)
+  }
+}

demo/apng/.gitignore

@@ -0,0 +1 @@
+/build

demo/apng/build.gradle.kts

@@ -0,0 +1,16 @@
+plugins {
+  id("signal-sample-app")
+  alias(libs.plugins.compose.compiler)
+}
+
+android {
+  namespace = "org.signal.apng"
+
+  defaultConfig {
+    applicationId = "org.signal.apng"
+  }
+}
+
+dependencies {
+  implementation(project(":lib:apng"))
+}

demo/apng/proguard-rules.pro

@@ -0,0 +1,21 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

demo/apng/src/main/AndroidManifest.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright 2024 Signal Messenger, LLC
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.Signal">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:label="@string/app_name"
+            android:theme="@style/Theme.Signal">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <activity
+            android:name=".DemoActivity"
+            android:exported="false"
+            android:theme="@style/Theme.Signal" />
+
+        <activity
+            android:name=".PlayerActivity"
+            android:exported="false"
+            android:theme="@style/Theme.Signal" />
+    </application>
+
+</manifest>

demo/apng/src/main/java/org/signal/apng/DemoActivity.kt

@@ -0,0 +1,298 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.apng
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.ImageView
+import android.widget.TextView
+import androidx.activity.ComponentActivity
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.ListAdapter
+import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.RecyclerView.ViewHolder
+
+class DemoActivity : ComponentActivity() {
+  override fun onCreate(savedInstanceState: Bundle?) {
+    super.onCreate(savedInstanceState)
+    setContentView(R.layout.demo_activity)
+
+    val myAdapter = MyAdapter()
+
+    findViewById<RecyclerView?>(R.id.list).apply {
+      layoutManager = LinearLayoutManager(this@DemoActivity)
+      adapter = myAdapter
+    }
+
+    // All test cases taken from:
+    // https://philip.html5.org/tests/apng/tests.html
+    myAdapter.submitList(
+      listOf(
+        TestModel.Heading("Basic cases"),
+        // TODO we don't yet render non-apngs
+//      TestModel(
+//        filename = "test00.png",
+//        description = "Trivial static image. This should be solid green."
+//      ),
+        TestModel.ApngModel(
+          filename = "test01.png",
+          description = "Trivial animated image - one frame; using default image. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test02.png",
+          description = "Trivial animated image - one frame; ignoring default image. This should be solid green."
+        ),
+
+        // IDAT, fdAT splitting
+        // TODO we don't yet support split IDAT/fdAT
+//      _root_ide_package_.org.signal.apng.MainActivity.TestModel.ApngModel(
+//        filename = "test03.png",
+//        description = "Basic split IDAT. This should be solid green."
+//      ),
+//      _root_ide_package_.org.signal.apng.MainActivity.TestModel.ApngModel(
+//        filename = "test04.png",
+//        description = "Split IDAT with zero-length chunk. This should be solid green."
+//      ),
+//      _root_ide_package_.org.signal.apng.MainActivity.TestModel.ApngModel(
+//        filename = "test05.png",
+//        description = "Basic split fdAT. This should be solid green."
+//      ),
+//      _root_ide_package_.org.signal.apng.MainActivity.TestModel.ApngModel(
+//        filename = "test06.png",
+//        description = "Split fdAT with zero-length chunk. This should be solid green."
+//      ),
+
+        TestModel.Heading("Dispose ops"),
+        TestModel.ApngModel(
+          filename = "test07.png",
+          description = "APNG_DISPOSE_OP_NONE - basic. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test08.png",
+          description = "APNG_DISPOSE_OP_BACKGROUND - basic. This should be transparent."
+        ),
+        TestModel.ApngModel(
+          filename = "test09.png",
+          description = "APNG_DISPOSE_OP_BACKGROUND - final frame. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test10.png",
+          description = "APNG_DISPOSE_OP_PREVIOUS - basic. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test11.png",
+          description = "APNG_DISPOSE_OP_PREVIOUS - final frame. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test12.png",
+          description = "APNG_DISPOSE_OP_PREVIOUS - first frame. This should be transparent."
+        ),
+
+        TestModel.Heading("Dispose ops and regions"),
+        TestModel.ApngModel(
+          filename = "test13.png",
+          description = "APNG_DISPOSE_OP_NONE in region. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test14.png",
+          description = "APNG_DISPOSE_OP_BACKGROUND before region. This should be transparent."
+        ),
+        TestModel.ApngModel(
+          filename = "test15.png",
+          description = "APNG_DISPOSE_OP_BACKGROUND in region. This should be a solid blue rectangle containing a smaller transparent rectangle."
+        ),
+        TestModel.ApngModel(
+          filename = "test16.png",
+          description = "APNG_DISPOSE_OP_PREVIOUS in region. This should be solid green."
+        ),
+
+        TestModel.Heading("Blend ops"),
+        TestModel.ApngModel(
+          filename = "test17.png",
+          description = "APNG_BLEND_OP_SOURCE on solid colour. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test18.png",
+          description = "APNG_BLEND_OP_SOURCE on transparent colour. This should be transparent."
+        ),
+        TestModel.ApngModel(
+          filename = "test19.png",
+          description = "APNG_BLEND_OP_SOURCE on nearly-transparent colour. This should be very nearly transparent."
+        ),
+        TestModel.ApngModel(
+          filename = "test20.png",
+          description = "APNG_BLEND_OP_OVER on solid and transparent colours. This should be solid green. "
+        ),
+        TestModel.ApngModel(
+          filename = "test21.png",
+          description = "APNG_BLEND_OP_OVER repeatedly with nearly-transparent colours. This should be solid green."
+        ),
+
+        TestModel.Heading("Blending and gamma"),
+        TestModel.ApngModel(
+          filename = "test22.png",
+          description = "APNG_BLEND_OP_OVER This should be solid slightly-dark green."
+        ),
+        TestModel.ApngModel(
+          filename = "test23.png",
+          description = "APNG_BLEND_OP_OVER This should be solid nearly-black."
+        ),
+
+        TestModel.Heading("Chunk ordering"),
+        TestModel.ApngModel(
+          filename = "test24.png",
+          description = "fcTL before acTL. This should be solid green."
+        ),
+
+        TestModel.Heading("Delays"),
+        TestModel.ApngModel(
+          filename = "test25.png",
+          description = "Basic delays. This should flash blue for half a second, then yellow for one second, then repeat."
+        ),
+        TestModel.ApngModel(
+          filename = "test26.png",
+          description = "Rounding of division. This should flash blue for half a second, then yellow for one second, then repeat."
+        ),
+        TestModel.ApngModel(
+          filename = "test27.png",
+          description = "16-bit numerator/denominator. This should flash blue for half a second, then yellow for one second, then repeat."
+        ),
+        TestModel.ApngModel(
+          filename = "test28.png",
+          description = "Zero denominator. This should flash blue for half a second, then yellow for one second, then repeat."
+        ),
+        TestModel.ApngModel(
+          filename = "test29.png",
+          description = "Zero numerator. This should flash cyan for a short period of time (perhaps zero), then magenta for the same short period of time, then blue for half a second, then yellow for one second, then repeat."
+        ),
+
+        TestModel.Heading("num_plays"),
+        TestModel.ApngModel(
+          filename = "test30.png",
+          description = "num_plays = 0. This should flash yellow for one second, then blue for one second, then repeat forever."
+        ),
+        TestModel.ApngModel(
+          filename = "test31.png",
+          description = "num_plays = 1. When first loaded, this should flash yellow for one second, then stay blue forever."
+        ),
+        TestModel.ApngModel(
+          filename = "test32.png",
+          description = "num_plays = 2. When first loaded, this should flash yellow for one second, then blue for one second, then yellow for one second, then blue forever."
+        ),
+
+        TestModel.Heading("Other depths and color types"),
+        TestModel.ApngModel(
+          filename = "test33.png",
+          description = "16-bit colour. This should be dark blue."
+        ),
+        TestModel.ApngModel(
+          filename = "test34.png",
+          description = "8-bit greyscale. This should be a solid grey rectangle containing a solid white rectangle."
+        ),
+        TestModel.ApngModel(
+          filename = "test35.png",
+          description = "8-bit greyscale and alpha, with blending. This should be solid grey."
+        ),
+        TestModel.ApngModel(
+          filename = "test36.png",
+          description = "2-color palette. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test37.png",
+          description = "2-bit palette and alpha. This should be solid green."
+        ),
+        TestModel.ApngModel(
+          filename = "test38.png",
+          description = "1-bit palette and alpha, with blending. This should be solid dark blue."
+        ),
+
+        TestModel.Heading("Random sample images"),
+        TestModel.ApngModel(
+          filename = "clock.png",
+          description = "A clock that uses BLEND_OP_OVER to draw moving hands."
+        ),
+        TestModel.ApngModel(
+          filename = "ball.png",
+          description = "Classic bouncing ball."
+        ),
+        TestModel.ApngModel(
+          filename = "elephant.png",
+          description = "A cute elephant"
+        )
+      )
+    )
+  }
+
+  sealed class TestModel {
+    data class Heading(val description: String) : TestModel()
+    data class ApngModel(val filename: String, val description: String) : TestModel()
+  }
+
+  private class MyAdapter : ListAdapter<TestModel, TestViewHolder>(object : DiffUtil.ItemCallback<TestModel>() {
+    override fun areItemsTheSame(oldItem: TestModel, newItem: TestModel): Boolean {
+      return oldItem == newItem
+    }
+
+    override fun areContentsTheSame(oldItem: TestModel, newItem: TestModel): Boolean {
+      return oldItem == newItem
+    }
+  }) {
+    override fun getItemViewType(position: Int): Int {
+      return when (getItem(position)) {
+        is TestModel.Heading -> 1
+        is TestModel.ApngModel -> 2
+      }
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TestViewHolder {
+      when (viewType) {
+        1 -> return TestViewHolder.HeadingViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.list_item_heading, parent, false))
+        2 -> return TestViewHolder.ApngViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.list_item_apng, parent, false))
+        else -> throw IllegalStateException()
+      }
+    }
+
+    override fun onBindViewHolder(holder: TestViewHolder, position: Int) {
+      holder.bind(getItem(position))
+    }
+  }
+
+  sealed class TestViewHolder(itemView: View) : ViewHolder(itemView) {
+    abstract fun bind(testModel: TestModel)
+
+    class HeadingViewHolder(itemView: View) : TestViewHolder(itemView) {
+      val description: TextView = itemView.findViewById(R.id.description)
+
+      override fun bind(testModel: TestModel) {
+        if (testModel !is TestModel.Heading) {
+          throw IllegalStateException()
+        }
+
+        description.text = testModel.description
+      }
+    }
+
+    class ApngViewHolder(itemView: View) : TestViewHolder(itemView) {
+      val description: TextView = itemView.findViewById(R.id.description)
+      val image: ImageView = itemView.findViewById(R.id.image)
+
+      override fun bind(testModel: TestModel) {
+        if (testModel !is TestModel.ApngModel) {
+          throw IllegalStateException()
+        }
+
+        description.text = testModel.description
+
+        val decoder = ApngDecoder(itemView.context.assets.open(testModel.filename))
+        val drawable = ApngDrawable(decoder)
+        image.setImageDrawable(drawable)
+      }
+    }
+  }
+}

demo/apng/src/main/java/org/signal/apng/MainActivity.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.apng
+
+import android.content.Intent
+import android.os.Bundle
+import android.widget.Button
+import androidx.activity.ComponentActivity
+
+class MainActivity : ComponentActivity() {
+  override fun onCreate(savedInstanceState: Bundle?) {
+    super.onCreate(savedInstanceState)
+    setContentView(R.layout.main_activity)
+
+    findViewById<Button>(R.id.demo_button).setOnClickListener {
+      startActivity(Intent(this, DemoActivity::class.java))
+    }
+    findViewById<Button>(R.id.player_button).setOnClickListener {
+      startActivity(Intent(this, PlayerActivity::class.java))
+    }
+  }
+}

demo/apng/src/main/java/org/signal/apng/PlayerActivity.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.apng
+
+import android.annotation.SuppressLint
+import android.os.Bundle
+import android.widget.Button
+import android.widget.ImageView
+import android.widget.TextView
+import androidx.activity.ComponentActivity
+
+class PlayerActivity : ComponentActivity() {
+  lateinit var frameMetadata: TextView
+  lateinit var disposeOpText: TextView
+  lateinit var blendOpText: TextView
+
+  override fun onCreate(savedInstanceState: Bundle?) {
+    super.onCreate(savedInstanceState)
+    setContentView(R.layout.player_activity)
+
+    val image = findViewById<ImageView>(R.id.player_image)
+    val prevButton = findViewById<Button>(R.id.prev_button)
+    val nextButton = findViewById<Button>(R.id.next_button)
+    frameMetadata = findViewById<TextView>(R.id.frame_metadata)
+
+    val decoder = ApngDecoder(assets.open("broken03.png"))
+    val drawable = ApngDrawable(decoder).apply {
+      stop()
+      debugDrawBounds = true
+    }
+
+    image.setImageDrawable(drawable)
+
+    prevButton.setOnClickListener {
+      drawable.prevFrame()
+      updateFrameInfo(drawable)
+    }
+
+    nextButton.setOnClickListener {
+      drawable.nextFrame()
+      updateFrameInfo(drawable)
+    }
+
+    updateFrameInfo(drawable)
+  }
+
+  @SuppressLint("SetTextI18n")
+  private fun updateFrameInfo(drawable: ApngDrawable) {
+    frameMetadata.text = """
+      Frame: ${drawable.position + 1}/${drawable.frameCount}
+      --
+      Width: ${drawable.currentFrame.fcTL.width}
+      Height: ${drawable.currentFrame.fcTL.height}
+      --
+      xOffset: ${drawable.currentFrame.fcTL.xOffset}
+      yOffset: ${drawable.currentFrame.fcTL.yOffset}
+      --
+      DisposeOp: ${drawable.currentFrame.fcTL.disposeOp.name}
+      BlendOp: ${drawable.currentFrame.fcTL.blendOp.name}
+      
+      WARNING: Going backwards can break rendering.
+    """.trimIndent()
+  }
+}

demo/apng/src/main/java/org/signal/apng/ui/theme/Color.kt

@@ -0,0 +1,11 @@
+package org.signal.apng.ui.theme
+
+import androidx.compose.ui.graphics.Color
+
+val Purple80 = Color(0xFFD0BCFF)
+val PurpleGrey80 = Color(0xFFCCC2DC)
+val Pink80 = Color(0xFFEFB8C8)
+
+val Purple40 = Color(0xFF6650a4)
+val PurpleGrey40 = Color(0xFF625b71)
+val Pink40 = Color(0xFF7D5260)

demo/apng/src/main/java/org/signal/apng/ui/theme/Theme.kt

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.apng.ui.theme
+
+import android.app.Activity
+import android.os.Build
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.darkColorScheme
+import androidx.compose.material3.dynamicDarkColorScheme
+import androidx.compose.material3.dynamicLightColorScheme
+import androidx.compose.material3.lightColorScheme
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.SideEffect
+import androidx.compose.ui.graphics.toArgb
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalView
+import androidx.core.view.WindowCompat
+
+private val DarkColorScheme = darkColorScheme(
+  primary = Purple80,
+  secondary = PurpleGrey80,
+  tertiary = Pink80
+)
+
+private val LightColorScheme = lightColorScheme(
+  primary = Purple40,
+  secondary = PurpleGrey40,
+  tertiary = Pink40
+
+  /* Other default colors to override
+    background = Color(0xFFFFFBFE),
+    surface = Color(0xFFFFFBFE),
+    onPrimary = Color.White,
+    onSecondary = Color.White,
+    onTertiary = Color.White,
+    onBackground = Color(0xFF1C1B1F),
+    onSurface = Color(0xFF1C1B1F),
+   */
+)
+
+@Composable
+fun SignalTheme(
+  darkTheme: Boolean = isSystemInDarkTheme(),
+  // Dynamic color is available on Android 12+
+  dynamicColor: Boolean = true,
+  content: @Composable () -> Unit
+) {
+  val colorScheme = when {
+    dynamicColor && Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
+      val context = LocalContext.current
+      if (darkTheme) dynamicDarkColorScheme(context) else dynamicLightColorScheme(context)
+    }
+
+    darkTheme -> DarkColorScheme
+    else -> LightColorScheme
+  }
+  val view = LocalView.current
+  if (!view.isInEditMode) {
+    SideEffect {
+      val window = (view.context as Activity).window
+      window.statusBarColor = colorScheme.primary.toArgb()
+      WindowCompat.getInsetsController(window, view).isAppearanceLightStatusBars = darkTheme
+    }
+  }
+
+  MaterialTheme(
+    colorScheme = colorScheme,
+    typography = Typography,
+    content = content
+  )
+}

demo/apng/src/main/java/org/signal/apng/ui/theme/Type.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.apng.ui.theme
+
+import androidx.compose.material3.Typography
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.sp
+
+// Set of Material typography styles to start with
+val Typography = Typography(
+  bodyLarge = TextStyle(
+    fontFamily = FontFamily.Default,
+    fontWeight = FontWeight.Normal,
+    fontSize = 16.sp,
+    lineHeight = 24.sp,
+    letterSpacing = 0.5.sp
+  )
+  /* Other default text styles to override
+    titleLarge = TextStyle(
+        fontFamily = FontFamily.Default,
+        fontWeight = FontWeight.Normal,
+        fontSize = 22.sp,
+        lineHeight = 28.sp,
+        letterSpacing = 0.sp
+    ),
+    labelSmall = TextStyle(
+        fontFamily = FontFamily.Default,
+        fontWeight = FontWeight.Medium,
+        fontSize = 11.sp,
+        lineHeight = 16.sp,
+        letterSpacing = 0.5.sp
+    )
+   */
+)

demo/apng/src/main/res/drawable-v24/ic_launcher_foreground.xml

@@ -0,0 +1,35 @@
+<!--
+  ~ Copyright 2024 Signal Messenger, LLC
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:aapt="http://schemas.android.com/aapt"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path android:pathData="M31,63.928c0,0 6.4,-11 12.1,-13.1c7.2,-2.6 26,-1.4 26,-1.4l38.1,38.1L107,108.928l-32,-1L31,63.928z">
+        <aapt:attr name="android:fillColor">
+            <gradient
+                android:endX="85.84757"
+                android:endY="92.4963"
+                android:startX="42.9492"
+                android:startY="49.59793"
+                android:type="linear">
+                <item
+                    android:color="#44000000"
+                    android:offset="0.0" />
+                <item
+                    android:color="#00000000"
+                    android:offset="1.0" />
+            </gradient>
+        </aapt:attr>
+    </path>
+    <path
+        android:fillColor="#FFFFFF"
+        android:fillType="nonZero"
+        android:pathData="M65.3,45.828l3.8,-6.6c0.2,-0.4 0.1,-0.9 -0.3,-1.1c-0.4,-0.2 -0.9,-0.1 -1.1,0.3l-3.9,6.7c-6.3,-2.8 -13.4,-2.8 -19.7,0l-3.9,-6.7c-0.2,-0.4 -0.7,-0.5 -1.1,-0.3C38.8,38.328 38.7,38.828 38.9,39.228l3.8,6.6C36.2,49.428 31.7,56.028 31,63.928h46C76.3,56.028 71.8,49.428 65.3,45.828zM43.4,57.328c-0.8,0 -1.5,-0.5 -1.8,-1.2c-0.3,-0.7 -0.1,-1.5 0.4,-2.1c0.5,-0.5 1.4,-0.7 2.1,-0.4c0.7,0.3 1.2,1 1.2,1.8C45.3,56.528 44.5,57.328 43.4,57.328L43.4,57.328zM64.6,57.328c-0.8,0 -1.5,-0.5 -1.8,-1.2s-0.1,-1.5 0.4,-2.1c0.5,-0.5 1.4,-0.7 2.1,-0.4c0.7,0.3 1.2,1 1.2,1.8C66.5,56.528 65.6,57.328 64.6,57.328L64.6,57.328z"
+        android:strokeWidth="1"
+        android:strokeColor="#00000000" />
+</vector>

demo/apng/src/main/res/drawable/ic_launcher_background.xml

@@ -0,0 +1,175 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright 2024 Signal Messenger, LLC
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillColor="#3DDC84"
+        android:pathData="M0,0h108v108h-108z" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M9,0L9,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,0L19,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M29,0L29,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M39,0L39,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M49,0L49,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M59,0L59,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M69,0L69,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M79,0L79,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M89,0L89,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M99,0L99,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,9L108,9"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,19L108,19"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,29L108,29"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,39L108,39"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,49L108,49"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,59L108,59"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,69L108,69"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,79L108,79"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,89L108,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,99L108,99"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,29L89,29"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,39L89,39"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,49L89,49"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,59L89,59"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,69L89,69"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,79L89,79"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M29,19L29,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M39,19L39,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M49,19L49,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M59,19L59,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M69,19L69,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M79,19L79,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+</vector>

demo/apng/src/main/res/layout/demo_activity.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    xmlns:tools="http://schemas.android.com/tools"
+    tools:context=".DemoActivity">
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/list"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+
+</LinearLayout>

demo/apng/src/main/res/layout/list_item_apng.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:layout_marginBottom="8dp"
+    android:padding="8dp">
+
+    <TextView
+        android:id="@+id/description"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="4dp"
+        android:text="@string/apng_description_placeholder"/>
+
+    <ImageView
+        android:id="@+id/image"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content" />
+
+</LinearLayout>

demo/apng/src/main/res/layout/list_item_heading.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:layout_marginBottom="8dp"
+    android:padding="8dp">
+
+    <TextView
+        android:id="@+id/description"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="4dp"
+        android:textAppearance="@android:style/TextAppearance.Material.Headline"
+        tools:text="Some title"/>
+
+</LinearLayout>

demo/apng/src/main/res/layout/main_activity.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    android:gravity="center_vertical"
+    xmlns:tools="http://schemas.android.com/tools"
+    tools:context=".DemoActivity">
+
+    <Button
+        android:id="@+id/demo_button"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="@string/apng_demo" />
+
+    <Button
+        android:id="@+id/player_button"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="@string/apng_player" />
+
+</LinearLayout>

demo/apng/src/main/res/layout/player_activity.xml

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    android:gravity="center"
+    xmlns:tools="http://schemas.android.com/tools"
+    tools:context=".DemoActivity">
+
+    <ImageView
+        android:id="@+id/player_image"
+        android:layout_width="300dp"
+        android:layout_height="300dp" />
+
+    <LinearLayout
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal">
+
+        <Button
+            android:id="@+id/prev_button"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/apng_prev" />
+
+        <Button
+            android:id="@+id/next_button"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/apng_next" />
+    </LinearLayout>
+
+    <TextView
+        android:id="@+id/frame_metadata"
+        android:layout_width="250dp"
+        android:layout_height="wrap_content"
+        tools:text="10/15" />
+
+</LinearLayout>

demo/apng/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright 2024 Signal Messenger, LLC
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+    <monochrome android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

demo/apng/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright 2024 Signal Messenger, LLC
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+    <monochrome android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

demo/apng/src/main/res/values/colors.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright 2024 Signal Messenger, LLC
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+
+<resources>
+    <color name="purple_200">#FFBB86FC</color>
+    <color name="purple_500">#FF6200EE</color>
+    <color name="purple_700">#FF3700B3</color>
+    <color name="teal_200">#FF03DAC5</color>
+    <color name="teal_700">#FF018786</color>
+    <color name="black">#FF000000</color>
+    <color name="white">#FFFFFFFF</color>
+</resources>

demo/apng/src/main/res/values/strings.xml

@@ -0,0 +1,13 @@
+<!--
+  ~ Copyright 2024 Signal Messenger, LLC
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+
+<resources>
+    <string name="app_name">apng-app</string>
+    <string name="apng_description_placeholder">idk</string>
+    <string name="apng_demo">Demo</string>
+    <string name="apng_player">Player</string>
+    <string name="apng_prev">Prev</string>
+    <string name="apng_next">Next</string>
+</resources>

demo/apng/src/main/res/values/themes.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright 2024 Signal Messenger, LLC
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+
+<resources>
+
+    <style name="Theme.Signal" parent="android:Theme.Material.Light.NoActionBar" />
+</resources>

demo/apng/src/test/java/org/signal/apng/ExampleUnitTest.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.apng
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+/**
+ * Example local unit test, which will execute on the development machine (host).
+ *
+ * See [testing documentation](http://d.android.com/tools/testing).
+ */
+class ExampleUnitTest {
+  @Test
+  fun addition_isCorrect() {
+    assertEquals(4, 2 + 2)
+  }
+}

lib/apng/.gitignore

@@ -0,0 +1 @@
+/build

lib/apng/build.gradle.kts

@@ -0,0 +1,13 @@
+plugins {
+  id("signal-library")
+}
+
+android {
+  namespace = "org.signal.apng"
+}
+
+dependencies {
+  implementation(project(":core:util"))
+  testImplementation(testLibs.junit.junit)
+  testImplementation(testLibs.robolectric.robolectric)
+}

lib/apng/proguard-rules.pro

@@ -0,0 +1,21 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile