ladybird/Libraries/LibWeb/Compositor/AsyncScrollTree.cpp
Andreas Kling ce1521441f LibWeb: Reject async wheels over nested navigables
Add main-thread wheel regions to async scrolling snapshots for embedded
navigable containers. A viewport scroll node covers the iframe box, so
the compositor must explicitly treat that rectangle as a synchronous
routing boundary before it accepts a UI-process wheel bypass.

Hit-test those regions in both internals admission and the compositor's
async enqueue path. The enqueue path now stores the hit-tested scroll
target in the queued command, ensuring accepted input is applied to the
same target that passed admission instead of being reselected later.

Add a text test for iframe routing. A wheel over the nested navigable is
rejected for async scrolling, while a wheel over the parent viewport
remains admitted.
2026-05-12 20:57:08 +02:00

309 lines
13 KiB
C++

/*
* Copyright (c) 2026-present, the Ladybird developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Compositor/AsyncScrollTree.h>
#include <LibWeb/Painting/DisplayList.h>
#include <AK/Debug.h>
namespace Web::Compositor {
void AsyncScrollTree::set_state(AsyncScrollingState&& state)
{
m_scroll_nodes = move(state.scroll_nodes);
m_sticky_areas = move(state.sticky_areas);
m_main_thread_wheel_event_regions = move(state.main_thread_wheel_event_regions);
m_viewport_rect = state.viewport_rect;
m_main_thread_wheel_event_targets.clear();
m_wheel_scroll_targets.clear();
}
AsyncScrollNode* AsyncScrollTree::scroll_node_for_id(AsyncScrollNodeID node_id)
{
for (auto& node : m_scroll_nodes) {
if (node.node_id == node_id)
return &node;
}
return nullptr;
}
AsyncScrollNode const* AsyncScrollTree::scroll_node_for_id(AsyncScrollNodeID node_id) const
{
for (auto const& node : m_scroll_nodes) {
if (node.node_id == node_id)
return &node;
}
return nullptr;
}
AsyncStickyArea const* AsyncScrollTree::sticky_area_for_scroll_frame_index(Painting::ScrollFrameIndex scroll_frame_index) const
{
for (auto const& sticky_area : m_sticky_areas) {
if (sticky_area.scroll_frame_index == scroll_frame_index)
return &sticky_area;
}
return nullptr;
}
Gfx::FloatPoint AsyncScrollTree::clamp_scroll_offset_to_node(AsyncScrollNode const& node, Gfx::FloatPoint scroll_offset)
{
scroll_offset.set_x(max(0.0f, min(scroll_offset.x(), node.max_scroll_offset.x())));
scroll_offset.set_y(max(0.0f, min(scroll_offset.y(), node.max_scroll_offset.y())));
return scroll_offset;
}
bool AsyncScrollTree::can_scroll_node_by_delta(AsyncScrollNode const& node, Gfx::FloatPoint delta)
{
if (delta.x() < 0 && node.scroll_offset.x() > 0)
return true;
if (delta.x() > 0 && node.scroll_offset.x() < node.max_scroll_offset.x())
return true;
if (delta.y() < 0 && node.scroll_offset.y() > 0)
return true;
if (delta.y() > 0 && node.scroll_offset.y() < node.max_scroll_offset.y())
return true;
return false;
}
bool AsyncScrollTree::can_scroll_target_by_delta(WheelScrollTarget const& target, Gfx::FloatPoint delta)
{
if (delta.x() < 0 && target.can_scroll_left)
return true;
if (delta.x() > 0 && target.can_scroll_right)
return true;
if (delta.y() < 0 && target.can_scroll_up)
return true;
if (delta.y() > 0 && target.can_scroll_down)
return true;
return false;
}
bool AsyncScrollTree::has_non_zero_scroll_delta(Gfx::FloatPoint delta)
{
return delta.x() != 0 || delta.y() != 0;
}
Optional<AsyncScrollNodeID> AsyncScrollTree::scrollable_ancestor_for_node(AsyncScrollNodeID node_id, Gfx::FloatPoint delta) const
{
auto const* node = scroll_node_for_id(node_id);
if (!node)
return {};
auto parent_node_id = node->parent_node_id;
while (parent_node_id.has_value()) {
auto const* parent_node = scroll_node_for_id(*parent_node_id);
if (!parent_node)
return {};
if (can_scroll_node_by_delta(*parent_node, delta))
return *parent_node_id;
parent_node_id = parent_node->parent_node_id;
}
return {};
}
Optional<Painting::ScrollFrameIndex> AsyncScrollTree::parent_scroll_frame_index(Painting::ScrollFrameIndex scroll_frame_index) const
{
for (auto const& node : m_scroll_nodes) {
if (node.node_id.scroll_frame_index != scroll_frame_index)
continue;
if (!node.parent_node_id.has_value())
return {};
return node.parent_node_id->scroll_frame_index;
}
if (auto const* sticky_area = sticky_area_for_scroll_frame_index(scroll_frame_index))
return sticky_area->parent_scroll_frame_index;
return {};
}
Gfx::FloatPoint AsyncScrollTree::cumulative_device_offset_for_frame(Painting::ScrollFrameIndex scroll_frame_index, Painting::ScrollStateSnapshot const& scroll_state_snapshot) const
{
Gfx::FloatPoint offset;
for (auto index = scroll_frame_index; index.value();) {
offset.translate_by(scroll_state_snapshot.device_offset_for_index(index));
auto parent_index = parent_scroll_frame_index(index);
if (!parent_index.has_value())
break;
index = *parent_index;
}
return offset;
}
Gfx::FloatPoint AsyncScrollTree::apply_scroll_delta_to_node(AsyncScrollNode& node, Gfx::FloatPoint delta, Painting::ScrollStateSnapshot& scroll_state_snapshot)
{
auto old_scroll_offset = node.scroll_offset;
auto new_scroll_offset = clamp_scroll_offset_to_node(node, old_scroll_offset.translated(delta));
if (new_scroll_offset == old_scroll_offset) {
dbgln_if(COMPOSITOR_DEBUG, "[Compositor] Async scroll node {} did not move for delta {},{} (offset={},{} max={},{})",
node.node_id.scroll_frame_index.value(), delta.x(), delta.y(), old_scroll_offset.x(), old_scroll_offset.y(), node.max_scroll_offset.x(), node.max_scroll_offset.y());
return delta;
}
node.scroll_offset = new_scroll_offset;
scroll_state_snapshot.set_device_offset_for_index(node.node_id.scroll_frame_index, { -new_scroll_offset.x(), -new_scroll_offset.y() });
Gfx::FloatPoint consumed_delta {
new_scroll_offset.x() - old_scroll_offset.x(),
new_scroll_offset.y() - old_scroll_offset.y()
};
dbgln_if(COMPOSITOR_DEBUG, "[Compositor] Async scroll node {} moved from {},{} to {},{} (consumed={},{} remaining={},{})",
node.node_id.scroll_frame_index.value(),
old_scroll_offset.x(), old_scroll_offset.y(),
new_scroll_offset.x(), new_scroll_offset.y(),
consumed_delta.x(), consumed_delta.y(),
delta.x() - consumed_delta.x(), delta.y() - consumed_delta.y());
return {
delta.x() - consumed_delta.x(),
delta.y() - consumed_delta.y()
};
}
void AsyncScrollTree::update_sticky_offsets(Painting::ScrollStateSnapshot& scroll_state_snapshot) const
{
// This mirrors ViewportPaintable::refresh_scroll_state(), but consumes the compositor's mutated
// ScrollStateSnapshot instead of live layout objects.
for (auto const& sticky_area : m_sticky_areas) {
if (!sticky_area.nearest_scrolling_ancestor_index.value())
continue;
Gfx::FloatPoint parent_sticky_offset;
if (sticky_area.parent_scroll_frame_index.value() && sticky_area_for_scroll_frame_index(sticky_area.parent_scroll_frame_index))
parent_sticky_offset = cumulative_device_offset_for_frame(sticky_area.parent_scroll_frame_index, scroll_state_snapshot);
auto sticky_position_in_ancestor = sticky_area.position_relative_to_scroll_ancestor.translated(parent_sticky_offset);
auto containing_block_region = sticky_area.containing_block_region;
if (sticky_area.needs_parent_offset_adjustment)
containing_block_region.translate_by(parent_sticky_offset);
auto min_offset_within_containing_block = containing_block_region.top_left();
Gfx::FloatPoint max_offset_within_containing_block {
containing_block_region.right() - sticky_area.border_box_size.width(),
containing_block_region.bottom() - sticky_area.border_box_size.height()
};
auto ancestor_device_offset = scroll_state_snapshot.device_offset_for_index(sticky_area.nearest_scrolling_ancestor_index);
Gfx::FloatPoint scroll_ancestor_scroll_offset { -ancestor_device_offset.x(), -ancestor_device_offset.y() };
Gfx::FloatRect scrollport_rect { scroll_ancestor_scroll_offset, sticky_area.scrollport_size };
Gfx::FloatPoint sticky_offset;
if (sticky_area.inset_top.has_value()) {
if (scrollport_rect.top() > sticky_position_in_ancestor.y() - *sticky_area.inset_top)
sticky_offset.set_y(min(scrollport_rect.top() + *sticky_area.inset_top, max_offset_within_containing_block.y()) - sticky_position_in_ancestor.y());
}
if (sticky_area.inset_left.has_value()) {
if (scrollport_rect.left() > sticky_position_in_ancestor.x() - *sticky_area.inset_left)
sticky_offset.set_x(min(scrollport_rect.left() + *sticky_area.inset_left, max_offset_within_containing_block.x()) - sticky_position_in_ancestor.x());
}
if (sticky_area.inset_bottom.has_value()) {
if (scrollport_rect.bottom() < sticky_position_in_ancestor.y() + sticky_area.border_box_size.height() + *sticky_area.inset_bottom)
sticky_offset.set_y(max(scrollport_rect.bottom() - sticky_area.border_box_size.height() - *sticky_area.inset_bottom, min_offset_within_containing_block.y()) - sticky_position_in_ancestor.y());
}
if (sticky_area.inset_right.has_value()) {
if (scrollport_rect.right() < sticky_position_in_ancestor.x() + sticky_area.border_box_size.width() + *sticky_area.inset_right)
sticky_offset.set_x(max(scrollport_rect.right() - sticky_area.border_box_size.width() - *sticky_area.inset_right, min_offset_within_containing_block.x()) - sticky_position_in_ancestor.x());
}
scroll_state_snapshot.set_device_offset_for_index(sticky_area.scroll_frame_index, sticky_offset);
}
}
bool AsyncScrollTree::apply_scroll_delta(AsyncScrollNodeID node_id, Gfx::FloatPoint delta, Painting::ScrollStateSnapshot& scroll_state_snapshot)
{
// The compositor can advance only the scroll offsets it owns in this snapshot. When a target reaches an edge,
// the remaining wheel delta is handed to the nearest scrollable ancestor from the same immutable tree.
bool scrolled = false;
auto remaining_delta = delta;
for (size_t remaining_handoffs = m_scroll_nodes.size(); remaining_handoffs > 0 && has_non_zero_scroll_delta(remaining_delta); --remaining_handoffs) {
auto* node = scroll_node_for_id(node_id);
if (!node)
break;
auto delta_before_scroll = remaining_delta;
remaining_delta = apply_scroll_delta_to_node(*node, remaining_delta, scroll_state_snapshot);
if (remaining_delta != delta_before_scroll)
scrolled = true;
if (!has_non_zero_scroll_delta(remaining_delta))
break;
auto ancestor_node_id = scrollable_ancestor_for_node(node_id, remaining_delta);
if (!ancestor_node_id.has_value())
break;
node_id = *ancestor_node_id;
}
if (scrolled)
update_sticky_offsets(scroll_state_snapshot);
else
dbgln_if(COMPOSITOR_DEBUG, "[Compositor] Async scroll tree did not scroll any node for delta {},{}",
delta.x(), delta.y());
return scrolled;
}
void AsyncScrollTree::rebuild_wheel_scroll_targets(RefPtr<Painting::DisplayList> const& display_list, Painting::ScrollStateSnapshot const& scroll_state_snapshot)
{
m_wheel_scroll_targets.clear();
m_main_thread_wheel_event_targets.clear();
if (!display_list)
return;
auto const& visual_context_tree = display_list->visual_context_tree();
for (auto const& node : m_scroll_nodes) {
auto viewport_rect = node.is_viewport
? Gfx::FloatRect { {}, m_viewport_rect.size().to_type<float>() }
: visual_context_tree.transform_rect_to_viewport(node.hit_test_visual_context_index, node.scrollport_rect.to_type<float>(), scroll_state_snapshot);
m_wheel_scroll_targets.append({
.node_id = node.node_id,
.viewport_rect = viewport_rect,
.can_scroll_left = node.scroll_offset.x() > 0,
.can_scroll_right = node.scroll_offset.x() < node.max_scroll_offset.x(),
.can_scroll_up = node.scroll_offset.y() > 0,
.can_scroll_down = node.scroll_offset.y() < node.max_scroll_offset.y(),
});
}
for (auto const& region : m_main_thread_wheel_event_regions) {
m_main_thread_wheel_event_targets.append({
.viewport_rect = visual_context_tree.transform_rect_to_viewport(region.visual_context_index, region.rect, scroll_state_snapshot),
});
}
}
void AsyncScrollTree::clear_wheel_scroll_targets()
{
m_wheel_scroll_targets.clear();
m_main_thread_wheel_event_targets.clear();
}
Optional<Gfx::FloatPoint> AsyncScrollTree::scroll_offset_for_node(AsyncScrollNodeID node_id) const
{
if (auto const* node = scroll_node_for_id(node_id))
return node->scroll_offset;
return {};
}
Optional<AsyncScrollNodeID> AsyncScrollTree::hit_test_scroll_node_for_wheel(Gfx::FloatPoint position, Gfx::FloatPoint delta) const
{
for (auto const& target : m_main_thread_wheel_event_targets) {
if (target.viewport_rect.contains(position))
return {};
}
Optional<AsyncScrollNodeID> scroll_target;
for (auto const& target : m_wheel_scroll_targets) {
if (!target.viewport_rect.contains(position))
continue;
if (!can_scroll_target_by_delta(target, delta))
continue;
scroll_target = target.node_id;
}
return scroll_target;
}
}