LibWeb+WebContent+WebWorker: Move backing store allocation in Navigable

Making navigables responsible for backing store allocation will allow us
to have separate backing stores for iframes and run paint updates for
them independently, which is a step toward isolating them into separate
processes.

Another nice side effect is that now Skia backend context is ready by
the time backing stores are allocated, so we will be able to get rid of
BackingStore class in the upcoming changes and allocate PaintingSurface
directly.

Libraries/LibWeb/Painting/BackingStore.h

@@ -8,6 +8,7 @@
 
 #include <AK/AtomicRefCounted.h>
 #include <AK/Noncopyable.h>
+#include <LibGfx/Bitmap.h>
 #include <LibGfx/Size.h>
 
 #ifdef AK_OS_MACOS

Libraries/LibWeb/Painting/BackingStoreManager.cpp

@@ -0,0 +1,146 @@
+/*
+ * Copyright (c) 2024, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/Timer.h>
+#include <LibWeb/HTML/TraversableNavigable.h>
+#include <LibWeb/Painting/BackingStoreManager.h>
+#include <WebContent/PageClient.h>
+
+#ifdef AK_OS_MACOS
+#    include <LibCore/IOSurface.h>
+#    include <LibCore/MachPort.h>
+#    include <LibCore/Platform/MachMessageTypes.h>
+#endif
+
+namespace Web::Painting {
+
+GC_DEFINE_ALLOCATOR(BackingStoreManager);
+
+#ifdef AK_OS_MACOS
+static Optional<Core::MachPort> s_browser_mach_port;
+void BackingStoreManager::set_browser_mach_port(Core::MachPort&& port)
+{
+    s_browser_mach_port = move(port);
+}
+#endif
+
+BackingStoreManager::BackingStoreManager(HTML::Navigable& navigable)
+    : m_navigable(navigable)
+{
+    m_backing_store_shrink_timer = Core::Timer::create_single_shot(3000, [this] {
+        resize_backing_stores_if_needed(WindowResizingInProgress::No);
+    });
+}
+
+void BackingStoreManager::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_navigable);
+}
+
+void BackingStoreManager::restart_resize_timer()
+{
+    m_backing_store_shrink_timer->restart();
+}
+
+void BackingStoreManager::reallocate_backing_stores(Gfx::IntSize size)
+{
+#ifdef AK_OS_MACOS
+    if (m_navigable->is_top_level_traversable() && s_browser_mach_port.has_value()) {
+        auto back_iosurface = Core::IOSurfaceHandle::create(size.width(), size.height());
+        auto back_iosurface_port = back_iosurface.create_mach_port();
+
+        auto front_iosurface = Core::IOSurfaceHandle::create(size.width(), size.height());
+        auto front_iosurface_port = front_iosurface.create_mach_port();
+
+        m_front_bitmap_id = m_next_bitmap_id++;
+        m_back_bitmap_id = m_next_bitmap_id++;
+
+        auto& page_client = m_navigable->top_level_traversable()->page().client();
+
+        Core::Platform::BackingStoreMetadata metadata;
+        metadata.page_id = page_client.id();
+        metadata.front_backing_store_id = m_front_bitmap_id;
+        metadata.back_backing_store_id = m_back_bitmap_id;
+
+        Core::Platform::MessageWithBackingStores message;
+
+        message.header.msgh_remote_port = s_browser_mach_port->port();
+        message.header.msgh_local_port = MACH_PORT_NULL;
+        message.header.msgh_bits = MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND, 0) | MACH_MSGH_BITS_COMPLEX;
+        message.header.msgh_size = sizeof(message);
+        message.header.msgh_id = Core::Platform::BACKING_STORE_IOSURFACES_MESSAGE_ID;
+
+        message.body.msgh_descriptor_count = 2;
+
+        message.front_descriptor.name = front_iosurface_port.release();
+        message.front_descriptor.disposition = MACH_MSG_TYPE_MOVE_SEND;
+        message.front_descriptor.type = MACH_MSG_PORT_DESCRIPTOR;
+
+        message.back_descriptor.name = back_iosurface_port.release();
+        message.back_descriptor.disposition = MACH_MSG_TYPE_MOVE_SEND;
+        message.back_descriptor.type = MACH_MSG_PORT_DESCRIPTOR;
+
+        message.metadata = metadata;
+
+        mach_msg_timeout_t const timeout = 100; // milliseconds
+        auto const send_result = mach_msg(&message.header, MACH_SEND_MSG | MACH_SEND_TIMEOUT, message.header.msgh_size, 0, MACH_PORT_NULL, timeout, MACH_PORT_NULL);
+        if (send_result != KERN_SUCCESS) {
+            dbgln("Failed to send message to server: {}", mach_error_string(send_result));
+            VERIFY_NOT_REACHED();
+        }
+
+        m_front_store = IOSurfaceBackingStore::create(move(front_iosurface));
+        m_back_store = IOSurfaceBackingStore::create(move(back_iosurface));
+
+        return;
+    }
+#endif
+
+    m_front_bitmap_id = m_next_bitmap_id++;
+    m_back_bitmap_id = m_next_bitmap_id++;
+
+    auto front_bitmap = Gfx::Bitmap::create_shareable(Gfx::BitmapFormat::BGRA8888, Gfx::AlphaType::Premultiplied, size).release_value();
+    auto back_bitmap = Gfx::Bitmap::create_shareable(Gfx::BitmapFormat::BGRA8888, Gfx::AlphaType::Premultiplied, size).release_value();
+
+    m_front_store = BitmapBackingStore::create(front_bitmap);
+    m_back_store = BitmapBackingStore::create(back_bitmap);
+
+    if (m_navigable->is_top_level_traversable()) {
+        auto& page_client = m_navigable->top_level_traversable()->page().client();
+        page_client.page_did_allocate_backing_stores(m_front_bitmap_id, front_bitmap->to_shareable_bitmap(), m_back_bitmap_id, back_bitmap->to_shareable_bitmap());
+    }
+}
+
+void BackingStoreManager::resize_backing_stores_if_needed(WindowResizingInProgress window_resize_in_progress)
+{
+    auto viewport_size = m_navigable->page().css_to_device_rect(m_navigable->viewport_rect()).size();
+    if (viewport_size.is_empty())
+        return;
+
+    Web::DevicePixelSize minimum_needed_size;
+    if (window_resize_in_progress == WindowResizingInProgress::Yes) {
+        // Pad the minimum needed size so that we don't have to keep reallocating backing stores while the window is being resized.
+        minimum_needed_size = { viewport_size.width() + 256, viewport_size.height() + 256 };
+    } else {
+        // If we're not in the middle of a resize, we can shrink the backing store size to match the viewport size.
+        minimum_needed_size = viewport_size;
+        m_front_store.clear();
+        m_back_store.clear();
+    }
+
+    if (!m_front_store || !m_back_store || !m_front_store->size().contains(minimum_needed_size.to_type<int>())) {
+        reallocate_backing_stores(minimum_needed_size.to_type<int>());
+    }
+}
+
+void BackingStoreManager::swap_back_and_front()
+{
+    swap(m_front_store, m_back_store);
+    swap(m_front_bitmap_id, m_back_bitmap_id);
+}
+
+}

Libraries/LibWeb/Painting/BackingStoreManager.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2024, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/HTML/Navigable.h>
+#include <LibWeb/Painting/BackingStore.h>
+
+namespace Web::Painting {
+
+class BackingStoreManager : public JS::Cell {
+    GC_CELL(BackingStoreManager, JS::Cell);
+    GC_DECLARE_ALLOCATOR(BackingStoreManager);
+
+public:
+#ifdef AK_OS_MACOS
+    static void set_browser_mach_port(Core::MachPort&&);
+#endif
+
+    enum class WindowResizingInProgress {
+        No,
+        Yes
+    };
+    void resize_backing_stores_if_needed(WindowResizingInProgress window_resize_in_progress);
+    void reallocate_backing_stores(Gfx::IntSize);
+    void restart_resize_timer();
+
+    struct BackingStore {
+        i32 bitmap_id { -1 };
+        Web::Painting::BackingStore* store { nullptr };
+    };
+
+    BackingStore acquire_store_for_next_frame()
+    {
+        BackingStore backing_store;
+        backing_store.bitmap_id = m_back_bitmap_id;
+        backing_store.store = m_back_store.ptr();
+        swap_back_and_front();
+        return backing_store;
+    }
+
+    virtual void visit_edges(Cell::Visitor& visitor) override;
+
+    BackingStoreManager(HTML::Navigable&);
+
+private:
+    void swap_back_and_front();
+
+    GC::Ref<HTML::Navigable> m_navigable;
+
+    i32 m_front_bitmap_id { -1 };
+    i32 m_back_bitmap_id { -1 };
+    RefPtr<Painting::BackingStore> m_front_store;
+    RefPtr<Painting::BackingStore> m_back_store;
+    int m_next_bitmap_id { 0 };
+
+    RefPtr<Core::Timer> m_backing_store_shrink_timer;
+};
+
+}

Libraries/LibWeb/Painting/NavigableContainerViewportPaintable.cpp

@@ -55,7 +55,7 @@ void NavigableContainerViewportPaintable::paint(PaintContext& context, PaintPhas
 
         context.display_list_recorder().add_clip_rect(clip_rect.to_type<int>());
 
-        DOM::Document::PaintConfig paint_config;
+        HTML::PaintConfig paint_config;
         paint_config.paint_overlay = context.should_paint_overlay();
         paint_config.should_show_line_box_borders = context.should_show_line_box_borders();
         auto display_list = const_cast<DOM::Document*>(hosted_document)->record_display_list(paint_config);