ImageDecoder: Handle decoding of images in an asynchronous manner

ImageDecoder now queues up image decoding requests and returns the
images back to the caller later. ImageDecoderClient has a new
promise-based API that allows callers to attach their own resolve/reject
handlers to the responses from ImageDecoder.

Userland/Libraries/LibImageDecoderClient/Client.cpp

@@ -16,48 +16,101 @@ Client::Client(NonnullOwnPtr<Core::LocalSocket> socket)
 
 void Client::die()
 {
+    for (auto& [_, promise] : m_pending_decoded_images) {
+        promise->reject(Error::from_string_literal("ImageDecoder disconnected"));
+    }
+    m_pending_decoded_images.clear();
+
     if (on_death)
         on_death();
 }
 
-Optional<DecodedImage> Client::decode_image(ReadonlyBytes encoded_data, Optional<Gfx::IntSize> ideal_size, Optional<ByteString> mime_type)
+NonnullRefPtr<Core::Promise<DecodedImage>> Client::decode_image(ReadonlyBytes encoded_data, Function<ErrorOr<void>(DecodedImage&)> on_resolved, Function<void(Error&)> on_rejected, Optional<Gfx::IntSize> ideal_size, Optional<ByteString> mime_type)
 {
-    if (encoded_data.is_empty())
-        return {};
+    auto promise = Core::Promise<DecodedImage>::construct();
+    if (on_resolved)
+        promise->on_resolution = move(on_resolved);
+    if (on_rejected)
+        promise->on_rejection = move(on_rejected);
+
+    if (encoded_data.is_empty()) {
+        promise->reject(Error::from_string_literal("No encoded data"));
+        return promise;
+    }
 
     auto encoded_buffer_or_error = Core::AnonymousBuffer::create_with_size(encoded_data.size());
     if (encoded_buffer_or_error.is_error()) {
-        dbgln("Could not allocate encoded buffer");
-        return {};
+        dbgln("Could not allocate encoded buffer: {}", encoded_buffer_or_error.error());
+        promise->reject(encoded_buffer_or_error.release_error());
+        return promise;
     }
     auto encoded_buffer = encoded_buffer_or_error.release_value();
 
     memcpy(encoded_buffer.data<void>(), encoded_data.data(), encoded_data.size());
-    auto response_or_error = try_decode_image(move(encoded_buffer), ideal_size, mime_type);
 
-    if (response_or_error.is_error()) {
-        dbgln("ImageDecoder died heroically");
-        return {};
+    auto response = send_sync_but_allow_failure<Messages::ImageDecoderServer::DecodeImage>(move(encoded_buffer), ideal_size, mime_type);
+    if (!response) {
+        dbgln("ImageDecoder disconnected trying to decode image");
+        promise->reject(Error::from_string_literal("ImageDecoder disconnected"));
+        return promise;
     }
 
-    auto& response = response_or_error.value();
+    m_pending_decoded_images.set(response->image_id(), promise);
 
-    if (response.bitmaps().is_empty())
+    return promise;
+}
+
+Optional<DecodedImage> Client::decode_image(ReadonlyBytes encoded_data, Optional<Gfx::IntSize> ideal_size, Optional<ByteString> mime_type)
+{
+    auto promise = decode_image(
+        encoded_data, [](auto) -> ErrorOr<void> { return {}; }, [](Error&) -> void {}, ideal_size, mime_type);
+    auto result = promise->await();
+    if (result.is_error())
         return {};
+    return result.release_value();
+}
+
+void Client::did_decode_image(i64 image_id, bool is_animated, u32 loop_count, Vector<Gfx::ShareableBitmap> const& bitmaps, Vector<u32> const& durations, Gfx::FloatPoint scale)
+{
+    VERIFY(!bitmaps.is_empty());
+
+    auto maybe_promise = m_pending_decoded_images.take(image_id);
+    if (!maybe_promise.has_value()) {
+        dbgln("ImageDecoderClient: No pending image with ID {}", image_id);
+        return;
+    }
+    auto promise = maybe_promise.release_value();
 
     DecodedImage image;
-    image.is_animated = response.is_animated();
-    image.loop_count = response.loop_count();
-    image.scale = response.scale();
-    image.frames.ensure_capacity(response.bitmaps().size());
-    auto bitmaps = response.take_bitmaps();
+    image.is_animated = is_animated;
+    image.loop_count = loop_count;
+    image.scale = scale;
+    image.frames.ensure_capacity(bitmaps.size());
     for (size_t i = 0; i < bitmaps.size(); ++i) {
-        if (!bitmaps[i].is_valid())
-            return {};
+        if (!bitmaps[i].is_valid()) {
+            dbgln("ImageDecoderClient: Invalid bitmap for request {} at index {}", image_id, i);
+            promise->reject(Error::from_string_literal("Invalid bitmap"));
+            return;
+        }
 
-        image.frames.empend(*bitmaps[i].bitmap(), response.durations()[i]);
+        image.frames.empend(*bitmaps[i].bitmap(), durations[i]);
     }
-    return image;
+
+    promise->resolve(move(image));
+}
+
+void Client::did_fail_to_decode_image(i64 image_id, String const& error_message)
+{
+    auto maybe_promise = m_pending_decoded_images.take(image_id);
+    if (!maybe_promise.has_value()) {
+        dbgln("ImageDecoderClient: No pending image with ID {}", image_id);
+        return;
+    }
+    auto promise = maybe_promise.release_value();
+
+    dbgln("ImageDecoderClient: Failed to decode image with ID {}: {}", image_id, error_message);
+    // FIXME: Include the error message in the Error object when Errors are allowed to hold Strings
+    promise->reject(Error::from_string_literal("Image decoding failed or aborted"));
 }
 
 }

Userland/Libraries/LibImageDecoderClient/Client.h

@@ -9,6 +9,7 @@
 #include <AK/HashMap.h>
 #include <ImageDecoder/ImageDecoderClientEndpoint.h>
 #include <ImageDecoder/ImageDecoderServerEndpoint.h>
+#include <LibCore/Promise.h>
 #include <LibIPC/ConnectionToServer.h>
 
 namespace ImageDecoderClient {
@@ -33,12 +34,20 @@ class Client final
 public:
     Client(NonnullOwnPtr<Core::LocalSocket>);
 
+    NonnullRefPtr<Core::Promise<DecodedImage>> decode_image(ReadonlyBytes, Function<ErrorOr<void>(DecodedImage&)> on_resolved, Function<void(Error&)> on_rejected, Optional<Gfx::IntSize> ideal_size = {}, Optional<ByteString> mime_type = {});
+
+    // FIXME: Move all clients to the promise-based API and get rid of this synchronous (i.e. EventLoop-spinning) one.
     Optional<DecodedImage> decode_image(ReadonlyBytes, Optional<Gfx::IntSize> ideal_size = {}, Optional<ByteString> mime_type = {});
 
     Function<void()> on_death;
 
 private:
     virtual void die() override;
+
+    virtual void did_decode_image(i64 image_id, bool is_animated, u32 loop_count, Vector<Gfx::ShareableBitmap> const& bitmaps, Vector<u32> const& durations, Gfx::FloatPoint scale) override;
+    virtual void did_fail_to_decode_image(i64 image_id, String const& error_message) override;
+
+    HashMap<i64, NonnullRefPtr<Core::Promise<DecodedImage>>> m_pending_decoded_images;
 };
 
 }

Userland/Services/ImageDecoder/ConnectionFromClient.cpp

@@ -72,20 +72,50 @@ static void decode_image_to_details(Core::AnonymousBuffer const& encoded_buffer,
     decode_image_to_bitmaps_and_durations_with_decoder(*decoder, ideal_size, bitmaps, durations);
 }
 
+ConnectionFromClient::Job ConnectionFromClient::make_decode_image_job(i64 image_id, Core::AnonymousBuffer encoded_buffer, Optional<Gfx::IntSize> ideal_size, Optional<ByteString> mime_type)
+{
+    return [strong_this = NonnullRefPtr(*this), image_id, encoded_buffer = move(encoded_buffer), ideal_size = move(ideal_size), mime_type = move(mime_type)]() {
+        bool is_animated = false;
+        u32 loop_count = 0;
+        Gfx::FloatPoint scale { 1, 1 };
+        Vector<Gfx::ShareableBitmap> bitmaps;
+        Vector<u32> durations;
+
+        decode_image_to_details(encoded_buffer, ideal_size, mime_type, is_animated, loop_count, bitmaps, durations, scale);
+        if (bitmaps.is_empty()) {
+            strong_this->async_did_fail_to_decode_image(image_id, "Could not decode image"_string);
+        } else {
+            strong_this->async_did_decode_image(image_id, is_animated, loop_count, bitmaps, durations, scale);
+        }
+    };
+}
+
 Messages::ImageDecoderServer::DecodeImageResponse ConnectionFromClient::decode_image(Core::AnonymousBuffer const& encoded_buffer, Optional<Gfx::IntSize> const& ideal_size, Optional<ByteString> const& mime_type)
 {
+    auto image_id = m_next_image_id++;
+
     if (!encoded_buffer.is_valid()) {
         dbgln_if(IMAGE_DECODER_DEBUG, "Encoded data is invalid");
-        return nullptr;
+        async_did_fail_to_decode_image(image_id, "Encoded data is invalid"_string);
+        return image_id;
     }
 
-    bool is_animated = false;
-    u32 loop_count = 0;
-    Gfx::FloatPoint scale { 1, 1 };
-    Vector<Gfx::ShareableBitmap> bitmaps;
-    Vector<u32> durations;
-    decode_image_to_details(encoded_buffer, ideal_size, mime_type, is_animated, loop_count, bitmaps, durations, scale);
-    return { is_animated, loop_count, bitmaps, durations, scale };
+    m_pending_jobs.set(image_id, make_decode_image_job(image_id, encoded_buffer, ideal_size, mime_type));
+
+    Core::deferred_invoke([strong_this = NonnullRefPtr(*this), image_id]() {
+        if (auto job = strong_this->m_pending_jobs.take(image_id); job.has_value()) {
+            job.value()();
+        }
+    });
+
+    return image_id;
+}
+
+void ConnectionFromClient::cancel_decoding(i64 image_id)
+{
+    if (auto job = m_pending_jobs.take(image_id); job.has_value()) {
+        async_did_fail_to_decode_image(image_id, "Decoding was canceled"_string);
+    }
 }
 
 }

Userland/Services/ImageDecoder/ConnectionFromClient.h

@@ -24,9 +24,17 @@ public:
     virtual void die() override;
 
 private:
+    using Job = Function<void()>;
+
     explicit ConnectionFromClient(NonnullOwnPtr<Core::LocalSocket>);
 
     virtual Messages::ImageDecoderServer::DecodeImageResponse decode_image(Core::AnonymousBuffer const&, Optional<Gfx::IntSize> const& ideal_size, Optional<ByteString> const& mime_type) override;
+    virtual void cancel_decoding(i64 image_id) override;
+
+    Job make_decode_image_job(i64 image_id, Core::AnonymousBuffer, Optional<Gfx::IntSize> ideal_size, Optional<ByteString> mime_type);
+
+    i64 m_next_image_id { 0 };
+    HashMap<i64, Job> m_pending_jobs;
 };
 
 }

Userland/Services/ImageDecoder/ImageDecoderClient.ipc

@@ -1,6 +1,7 @@
-#include <LibCore/AnonymousBuffer.h>
 #include <LibGfx/ShareableBitmap.h>
 
 endpoint ImageDecoderClient
 {
+    did_decode_image(i64 image_id, bool is_animated, u32 loop_count, Vector<Gfx::ShareableBitmap> bitmaps, Vector<u32> durations, Gfx::FloatPoint scale) =|
+    did_fail_to_decode_image(i64 image_id, String error_message) =|
 }

Userland/Services/ImageDecoder/ImageDecoderServer.ipc

@@ -1,7 +1,7 @@
 #include <LibCore/AnonymousBuffer.h>
-#include <LibGfx/ShareableBitmap.h>
 
 endpoint ImageDecoderServer
 {
-    decode_image(Core::AnonymousBuffer data, Optional<Gfx::IntSize> ideal_size, Optional<ByteString> mime_type) => (bool is_animated, u32 loop_count, Vector<Gfx::ShareableBitmap> bitmaps, Vector<u32> durations, Gfx::FloatPoint scale)
+    decode_image(Core::AnonymousBuffer data, Optional<Gfx::IntSize> ideal_size, Optional<ByteString> mime_type) => (i64 image_id)
+    cancel_decoding(i64 image_id) =|
 }