feat(mobile): add support for encoded image requests in local/remote image APIs (#26584)

* feat(mobile): add support for encoded image requests in local and remote image APIs

* fix(mobile): handle memory cleanup for cancelled image requests

* refactor(mobile): simplify memory management and response handling for encoded image requests

* fix(mobile): correct formatting in cancellation check for image requests

* Apply suggestion from @mertalev

Co-authored-by: Mert <101130780+mertalev@users.noreply.github.com>

* refactor(mobile): rename 'encoded' parameter to 'preferEncoded' for clarity in image request APIs

* fix(mobile): ensure proper resource cleanup for cancelled image requests

* refactor(mobile): streamline codec handling by removing unnecessary descriptor disposal in loadCodec request

---------

Co-authored-by: Mert <101130780+mertalev@users.noreply.github.com>

mobile/lib/infrastructure/loaders/image_request.dart

@@ -24,6 +24,8 @@ abstract class ImageRequest {
 
   Future<ImageInfo?> load(ImageDecoderCallback decode, {double scale = 1.0});
 
+  Future<ui.Codec?> loadCodec();
+
   void cancel() {
     if (_isCancelled) {
       return;
@@ -34,7 +36,7 @@ abstract class ImageRequest {
 
   void _onCancelled();
 
-  Future<ui.FrameInfo?> _fromEncodedPlatformImage(int address, int length) async {
+  Future<(ui.Codec, ui.ImageDescriptor)?> _codecFromEncodedPlatformImage(int address, int length) async {
     final pointer = Pointer<Uint8>.fromAddress(address);
     if (_isCancelled) {
       malloc.free(pointer);
@@ -67,6 +69,20 @@ abstract class ImageRequest {
       return null;
     }
 
+    return (codec, descriptor);
+  }
+
+  Future<ui.FrameInfo?> _fromEncodedPlatformImage(int address, int length) async {
+    final result = await _codecFromEncodedPlatformImage(address, length);
+    if (result == null) return null;
+
+    final (codec, descriptor) = result;
+    if (_isCancelled) {
+      descriptor.dispose();
+      codec.dispose();
+      return null;
+    }
+
     final frame = await codec.getNextFrame();
     descriptor.dispose();
     codec.dispose();

mobile/lib/infrastructure/loaders/local_image_request.dart

@@ -22,6 +22,7 @@ class LocalImageRequest extends ImageRequest {
       width: width,
       height: height,
       isVideo: assetType == AssetType.video,
+      preferEncoded: false,
     );
     if (info == null) {
       return null;
@@ -31,6 +32,26 @@ class LocalImageRequest extends ImageRequest {
     return frame == null ? null : ImageInfo(image: frame.image, scale: scale);
   }
 
+  @override
+  Future<ui.Codec?> loadCodec() async {
+    if (_isCancelled) {
+      return null;
+    }
+
+    final info = await localImageApi.requestImage(
+      localId,
+      requestId: requestId,
+      width: width,
+      height: height,
+      isVideo: assetType == AssetType.video,
+      preferEncoded: true,
+    );
+    if (info == null) return null;
+
+    final (codec, _) = await _codecFromEncodedPlatformImage(info['pointer']!, info['length']!) ?? (null, null);
+    return codec;
+  }
+
   @override
   Future<void> _onCancelled() {
     return localImageApi.cancelRequest(requestId);

mobile/lib/infrastructure/loaders/remote_image_request.dart

@@ -12,7 +12,8 @@ class RemoteImageRequest extends ImageRequest {
       return null;
     }
 
-    final info = await remoteImageApi.requestImage(uri, headers: headers, requestId: requestId);
+    final info = await remoteImageApi.requestImage(uri, headers: headers, requestId: requestId, preferEncoded: false);
+    // Android always returns encoded data, so we need to check for both shapes of the response.
     final frame = switch (info) {
       {'pointer': int pointer, 'length': int length} => await _fromEncodedPlatformImage(pointer, length),
       {'pointer': int pointer, 'width': int width, 'height': int height, 'rowBytes': int rowBytes} =>
@@ -22,6 +23,19 @@ class RemoteImageRequest extends ImageRequest {
     return frame == null ? null : ImageInfo(image: frame.image, scale: scale);
   }
 
+  @override
+  Future<ui.Codec?> loadCodec() async {
+    if (_isCancelled) {
+      return null;
+    }
+
+    final info = await remoteImageApi.requestImage(uri, headers: headers, requestId: requestId, preferEncoded: true);
+    if (info == null) return null;
+
+    final (codec, _) = await _codecFromEncodedPlatformImage(info['pointer']!, info['length']!) ?? (null, null);
+    return codec;
+  }
+
   @override
   Future<void> _onCancelled() {
     return remoteImageApi.cancelRequest(requestId);

mobile/lib/infrastructure/loaders/thumbhash_image_request.dart

@@ -16,6 +16,9 @@ class ThumbhashImageRequest extends ImageRequest {
     return frame == null ? null : ImageInfo(image: frame.image, scale: scale);
   }
 
+  @override
+  Future<ui.Codec?> loadCodec() => throw UnsupportedError('Thumbhash does not support codec loading');
+
   @override
   void _onCancelled() {}
 }