Files
ladybird/Libraries/LibWeb/CSS/FontLoading.cpp
Andreas Kling e1d35d7da9 LibWeb+LibGfx: Decompress WOFF2 fonts off the main thread
Add an off-thread preparation step for downloaded vector fonts so
WOFF2 resources can be decompressed before LibWeb tries to create a
typeface from them. This avoids doing the conversion work on the main
thread during @font-face loading.

Expose raw WOFF2-to-TTF conversion from LibGfx's WOFF2 loader and use
that from the new preparation path. Keeping the libwoff2 integration
in LibGfx preserves the layering between LibWeb and the third-party
decoder while still letting LibWeb schedule the work off-thread.
2026-04-18 23:46:20 +02:00

93 lines
3.6 KiB
C++

/*
* Copyright (c) 2026-present, the Ladybird developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Endian.h>
#include <LibCore/EventLoop.h>
#include <LibGfx/Font/WOFF/Loader.h>
#include <LibGfx/Font/WOFF2/Loader.h>
#include <LibThreading/ThreadPool.h>
#include <LibWeb/CSS/FontLoading.h>
namespace Web::CSS {
static constexpr u32 woff2_signature = 0x774F4632;
bool requires_off_thread_vector_font_preparation(ByteBuffer const& data, Optional<ByteString> const& mime_type_essence)
{
if (mime_type_essence == "font/woff2"sv || mime_type_essence == "application/font-woff2"sv)
return true;
if (data.size() < sizeof(u32))
return false;
auto signature = *bit_cast<BigEndian<u32> const*>(data.data());
return signature == woff2_signature;
}
static ErrorOr<PreparedVectorFontData> prepare_vector_font_data(ByteBuffer data, Optional<ByteString> mime_type_essence)
{
if (!requires_off_thread_vector_font_preparation(data, mime_type_essence))
return PreparedVectorFontData { .data = move(data), .mime_type_essence = move(mime_type_essence) };
return PreparedVectorFontData {
.data = TRY(WOFF2::convert_to_ttf(data)),
.mime_type_essence = ByteString { "font/ttf"sv }
};
}
ErrorOr<NonnullRefPtr<Gfx::Typeface const>> try_load_vector_font(ByteBuffer const& data, Optional<ByteString> const& mime_type_essence)
{
auto try_ttf = [&]() -> ErrorOr<NonnullRefPtr<Gfx::Typeface const>> {
return Gfx::Typeface::try_load_from_temporary_memory(data);
};
auto try_woff = [&]() -> ErrorOr<NonnullRefPtr<Gfx::Typeface const>> {
return WOFF::try_load_from_bytes(data);
};
auto try_woff2 = [&]() -> ErrorOr<NonnullRefPtr<Gfx::Typeface const>> {
return WOFF2::try_load_from_bytes(data);
};
if (mime_type_essence.has_value()) {
if (*mime_type_essence == "font/ttf"sv || *mime_type_essence == "application/x-font-ttf"sv || *mime_type_essence == "font/otf"sv)
return try_ttf();
if (*mime_type_essence == "font/woff"sv || *mime_type_essence == "application/font-woff"sv)
return try_woff();
if (*mime_type_essence == "font/woff2"sv || *mime_type_essence == "application/font-woff2"sv)
return try_woff2();
} else {
if (auto result = try_ttf(); !result.is_error())
return result.release_value();
if (auto result = try_woff(); !result.is_error())
return result.release_value();
if (auto result = try_woff2(); !result.is_error())
return result.release_value();
}
return Error::from_string_literal("Automatic format detection failed");
}
void prepare_vector_font_data_off_thread(ByteBuffer data, Function<void(ErrorOr<PreparedVectorFontData>)>&& on_complete, Optional<ByteString> mime_type_essence)
{
// Keep the callback on the origin thread so any GC roots it captures are
// also destroyed there.
auto* callback = new Function<void(ErrorOr<PreparedVectorFontData>)>(move(on_complete));
auto event_loop_weak = Core::EventLoop::current_weak();
Threading::ThreadPool::the().submit(
[data = move(data), callback, event_loop_weak = move(event_loop_weak), mime_type_essence = move(mime_type_essence)]() mutable {
auto result = prepare_vector_font_data(move(data), move(mime_type_essence));
auto origin = event_loop_weak->take();
if (!origin)
return;
origin->deferred_invoke([callback, result = move(result)]() mutable {
(*callback)(move(result));
delete callback;
});
});
}
}