From 0b9763cec500bea6ea46e47ccc9bff2ec018fa26 Mon Sep 17 00:00:00 2001
From: Jonah Williams <jonahwilliams@google.com>
Date: Tue, 12 Nov 2024 13:44:51 -0800
Subject: [PATCH] [Impeller] prevent no-op backend from throwing exceptions
 during image  decoding (flutter/engine#56522)

This preveents errors reported in some g3 test cases.
---
 .../flutter/lib/ui/painting/image_decoder_impeller.cc |  7 +++++++
 .../src/flutter/lib/ui/painting/multi_frame_codec.cc  | 11 +++++++++++
 2 files changed, 18 insertions(+)

diff --git a/engine/src/flutter/lib/ui/painting/image_decoder_impeller.cc b/engine/src/flutter/lib/ui/painting/image_decoder_impeller.cc
index 6a1118954a9..a73310c492b 100644
--- a/engine/src/flutter/lib/ui/painting/image_decoder_impeller.cc
+++ b/engine/src/flutter/lib/ui/painting/image_decoder_impeller.cc
@@ -519,6 +519,13 @@ void ImageDecoderImpeller::Decode(fml::RefPtr<ImageDescriptor> descriptor,
        result,
        supports_wide_gamut = supports_wide_gamut_,  //
        gpu_disabled_switch = gpu_disabled_switch_]() {
+#if FML_OS_IOS_SIMULATOR
+        // No-op backend.
+        if (!context) {
+          return;
+        }
+#endif  // FML_OS_IOS_SIMULATOR
+
         if (!context) {
           result(nullptr, "No Impeller context is available");
           return;
diff --git a/engine/src/flutter/lib/ui/painting/multi_frame_codec.cc b/engine/src/flutter/lib/ui/painting/multi_frame_codec.cc
index 1521c535fd9..f05ff111236 100644
--- a/engine/src/flutter/lib/ui/painting/multi_frame_codec.cc
+++ b/engine/src/flutter/lib/ui/painting/multi_frame_codec.cc
@@ -190,6 +190,17 @@ void MultiFrameCodec::State::GetNextFrameAndInvokeCallback(
     const std::shared_ptr<const fml::SyncSwitch>& gpu_disable_sync_switch,
     size_t trace_id,
     const std::shared_ptr<impeller::Context>& impeller_context) {
+#if FML_OS_IOS_SIMULATOR
+  // Noop backend.
+  if (!resourceContext && !impeller_context) {
+    ui_task_runner->PostTask(
+        fml::MakeCopyable([callback = std::move(callback)]() {
+          // must be destroyed on UI thread.
+        }));
+    return;
+  }
+#endif  // FML_OS_IOS_SIMULATOR
+
   fml::RefPtr<CanvasImage> image = nullptr;
   int duration = 0;
   sk_sp<DlImage> dlImage;