ladybird/Libraries/LibWeb/HTML/OffscreenCanvas.h
Timothy Flynn 64abc6101d LibWeb+WebWorker: Use IPC mechanics for structured serialization
Our structured serialization implementation had its own bespoke encoder
and decoder to serialize JS values. It also used a u32 buffer under the
hood, which made using its structures a bit awkward. We had previously
worked around its data structures in transferable streams, which nested
transfers of MessagePort instances. We basically had to add hooks into
the MessagePort to route to the correct transfer receiving steps, and
we could not invoke the correct AOs directly as the spec dictates.

We now use IPC mechanics to encode and decode data. This works because,
although we are encoding JS values, we are only ultimately encoding
primitive and basic AK types. The resulting data structures actually
enforce that we implement transferable streams exactly as the spec is
worded (I had planned to do that in a separate commit, but the fallout
of this patch actually required that change).
2025-07-18 10:09:02 -04:00

90 lines
3.2 KiB
C++

/*
* Copyright (c) 2025, Ladybird contributors
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <LibGfx/Bitmap.h>
#include <LibWeb/Bindings/PlatformObject.h>
#include <LibWeb/Bindings/Transferable.h>
#include <LibWeb/DOM/EventTarget.h>
#include <LibWeb/Forward.h>
#include <LibWeb/WebIDL/Types.h>
namespace Web::HTML {
// https://html.spec.whatwg.org/multipage/canvas.html#offscreenrenderingcontext
// NOTE: This is the Variant created by the IDL wrapper generator, and needs to be updated accordingly.
using OffscreenRenderingContext = Variant<GC::Root<OffscreenCanvasRenderingContext2D>, GC::Root<WebGL::WebGLRenderingContext>, GC::Root<WebGL::WebGL2RenderingContext>, Empty>;
// https://html.spec.whatwg.org/multipage/canvas.html#imageencodeoptions
struct ImageEncodeOptions {
FlyString type { "image/png"_fly_string };
Optional<double> quality;
};
// https://html.spec.whatwg.org/multipage/canvas.html#offscreencanvas
class OffscreenCanvas : public DOM::EventTarget
, public Web::Bindings::Transferable {
WEB_PLATFORM_OBJECT(OffscreenCanvas, DOM::EventTarget);
GC_DECLARE_ALLOCATOR(OffscreenCanvas);
public:
static GC::Ref<OffscreenCanvas> create(JS::Realm&, WebIDL::UnsignedLong width, WebIDL::UnsignedLong height);
static WebIDL::ExceptionOr<GC::Ref<OffscreenCanvas>> construct_impl(
JS::Realm&,
WebIDL::UnsignedLong width,
WebIDL::UnsignedLong height);
virtual ~OffscreenCanvas() override;
// ^Web::Bindings::Transferable
virtual WebIDL::ExceptionOr<void> transfer_steps(HTML::TransferDataEncoder&) override;
virtual WebIDL::ExceptionOr<void> transfer_receiving_steps(HTML::TransferDataDecoder&) override;
virtual HTML::TransferType primary_interface() const override;
WebIDL::UnsignedLong width() const;
WebIDL::UnsignedLong height() const;
RefPtr<Gfx::Bitmap> bitmap() const;
WebIDL::ExceptionOr<void> set_width(WebIDL::UnsignedLong);
WebIDL::ExceptionOr<void> set_height(WebIDL::UnsignedLong);
Gfx::IntSize bitmap_size_for_canvas() const;
JS::ThrowCompletionOr<OffscreenRenderingContext> get_context(Bindings::OffscreenRenderingContextId contextId, JS::Value options);
WebIDL::ExceptionOr<GC::Ref<ImageBitmap>> transfer_to_image_bitmap();
GC::Ref<WebIDL::Promise> convert_to_blob(Optional<ImageEncodeOptions> options);
void set_oncontextlost(GC::Ptr<WebIDL::CallbackType>);
GC::Ptr<WebIDL::CallbackType> oncontextlost();
void set_oncontextrestored(GC::Ptr<WebIDL::CallbackType>);
GC::Ptr<WebIDL::CallbackType> oncontextrestored();
private:
OffscreenCanvas(JS::Realm&, RefPtr<Gfx::Bitmap> bitmap);
virtual void initialize(JS::Realm&) override;
virtual void visit_edges(Cell::Visitor&) override;
enum class HasOrCreatedContext {
No,
Yes,
};
JS::ThrowCompletionOr<HasOrCreatedContext> create_2d_context(JS::Value options);
void reset_context_to_default_state();
void set_new_bitmap_size(Gfx::IntSize new_size);
Variant<GC::Ref<HTML::OffscreenCanvasRenderingContext2D>, GC::Ref<WebGL::WebGLRenderingContext>, GC::Ref<WebGL::WebGL2RenderingContext>, Empty> m_context;
RefPtr<Gfx::Bitmap> m_bitmap;
};
}