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LibWeb: Rework the layout engine to use relative offsets

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The box tree and line boxes now all store a relative offset from their
containing block, instead of an absolute (document-relative) position.

This removes a huge pain point from the layout system which was having
to adjust offsets recursively when something moved. It also makes some
layout logic significantly simpler.

Every box can still find its absolute position by walking its chain
of containing blocks and accumulating the translation from the root.
This is currently what we do both for rendering and hit testing.
This commit is contained in:
Andreas Kling 2020-06-10 10:42:29 +02:00
parent e836f09094
commit 656b01eb0f
21 changed files with 183 additions and 119 deletions
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45
Libraries/LibWeb/Layout/LayoutBox.cpp
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@ -203,9 +203,9 @@ void LayoutBox::render(RenderingContext& context)
#endif
Gfx::FloatRect padded_rect;
padded_rect.set_x(x() - box_model().padding().left.to_px(*this));
padded_rect.set_x(absolute_x() - box_model().padding().left.to_px(*this));
padded_rect.set_width(width() + box_model().padding().left.to_px(*this) + box_model().padding().right.to_px(*this));
padded_rect.set_y(y() - box_model().padding().top.to_px(*this));
padded_rect.set_y(absolute_y() - box_model().padding().top.to_px(*this));
padded_rect.set_height(height() + box_model().padding().top.to_px(*this) + box_model().padding().bottom.to_px(*this));
if (!is_body()) {
@ -237,7 +237,7 @@ void LayoutBox::render(RenderingContext& context)
LayoutNodeWithStyleAndBoxModelMetrics::render(context);
if (node() && document().inspected_node() == node())
context.painter().draw_rect(enclosing_int_rect(m_rect), Color::Magenta);
context.painter().draw_rect(enclosing_int_rect(absolute_rect()), Color::Magenta);
}
HitTestResult LayoutBox::hit_test(const Gfx::Point& position) const
@ -245,7 +245,7 @@ HitTestResult LayoutBox::hit_test(const Gfx::Point& position) const
// FIXME: It would be nice if we could confidently skip over hit testing
// parts of the layout tree, but currently we can't just check
// m_rect.contains() since inline text rects can't be trusted..
HitTestResult result { m_rect.contains(position.x(), position.y()) ? this : nullptr };
HitTestResult result { absolute_rect().contains(position.x(), position.y()) ? this : nullptr };
for_each_child([&](auto& child) {
auto child_result = child.hit_test(position);
if (child_result.layout_node)
@ -260,7 +260,7 @@ void LayoutBox::set_needs_display()
ASSERT(frame);
if (!is_inline()) {
const_cast<Frame*>(frame)->set_needs_display(enclosing_int_rect(rect()));
const_cast<Frame*>(frame)->set_needs_display(enclosing_int_rect(absolute_rect()));
return;
}
@ -272,12 +272,41 @@ bool LayoutBox::is_body() const
return node() && node() == document().body();
}
void LayoutBox::set_rect(const Gfx::FloatRect& rect)
void LayoutBox::set_offset(const Gfx::FloatPoint& offset)
{
if (m_rect == rect)
if (m_offset == offset)
return;
m_rect = rect;
m_offset = offset;
did_set_rect();
}
void LayoutBox::set_size(const Gfx::FloatSize& size)
{
if (m_size == size)
return;
m_size = size;
did_set_rect();
}
Gfx::FloatPoint LayoutBox::effective_offset() const
{
if (m_containing_line_box_fragment)
return m_containing_line_box_fragment->offset();
return m_offset;
}
const Gfx::FloatRect LayoutBox::absolute_rect() const
{
Gfx::FloatRect rect { effective_offset(), size() };
for (auto* block = containing_block(); block; block = block->containing_block()) {
rect.move_by(block->effective_offset());
}
return rect;
}
void LayoutBox::set_containing_line_box_fragment(LineBoxFragment& fragment)
{
m_containing_line_box_fragment = fragment.make_weak_ptr();
}
}