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ladybird/Userland/Libraries/LibWeb/Layout/SVGFormattingContext.cpp
MacDue dc9cb449b1 LibWeb: Store computed SVG path data/transforms in LayoutState 
This removes the awkward hack to recompute the layout transform at paint
time, and makes it possible for path sizes to be computed during layout.

For example, it's possible to use relative units in SVG shapes (e.g.
<rect>), which can be resolved during layout, but would be hard to
resolve again during painting.
2023-10-30 19:44:54 +01:00

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/*
* Copyright (c) 2021-2023, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
* Copyright (c) 2022, Tobias Christiansen <tobyase@serenityos.org>
* Copyright (c) 2023, MacDue <macdue@dueutil.tech>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Debug.h>
#include <LibWeb/Layout/BlockFormattingContext.h>
#include <LibWeb/Layout/SVGFormattingContext.h>
#include <LibWeb/Layout/SVGGeometryBox.h>
#include <LibWeb/Layout/SVGSVGBox.h>
#include <LibWeb/Layout/SVGTextBox.h>
#include <LibWeb/SVG/SVGForeignObjectElement.h>
#include <LibWeb/SVG/SVGSVGElement.h>
#include <LibWeb/SVG/SVGSymbolElement.h>
#include <LibWeb/SVG/SVGUseElement.h>
namespace Web::Layout {
SVGFormattingContext::SVGFormattingContext(LayoutState& state, Box const& box, FormattingContext* parent)
: FormattingContext(Type::SVG, state, box, parent)
{
}
SVGFormattingContext::~SVGFormattingContext() = default;
CSSPixels SVGFormattingContext::automatic_content_width() const
{
return 0;
}
CSSPixels SVGFormattingContext::automatic_content_height() const
{
return 0;
}
struct ViewBoxTransform {
CSSPixelPoint offset;
double scale_factor;
};
// https://svgwg.org/svg2-draft/coords.html#PreserveAspectRatioAttribute
static ViewBoxTransform scale_and_align_viewbox_content(SVG::PreserveAspectRatio const& preserve_aspect_ratio,
SVG::ViewBox const& view_box, Gfx::FloatSize viewbox_scale, auto const& svg_box_state)
{
ViewBoxTransform viewbox_transform {};
switch (preserve_aspect_ratio.meet_or_slice) {
case SVG::PreserveAspectRatio::MeetOrSlice::Meet:
// meet (the default) - Scale the graphic such that:
// - aspect ratio is preserved
// - the entire ‘viewBox’ is visible within the SVG viewport
// - the ‘viewBox’ is scaled up as much as possible, while still meeting the other criteria
viewbox_transform.scale_factor = min(viewbox_scale.width(), viewbox_scale.height());
break;
case SVG::PreserveAspectRatio::MeetOrSlice::Slice:
// slice - Scale the graphic such that:
// aspect ratio is preserved
// the entire SVG viewport is covered by the ‘viewBox’
// the ‘viewBox’ is scaled down as much as possible, while still meeting the other criteria
viewbox_transform.scale_factor = max(viewbox_scale.width(), viewbox_scale.height());
break;
default:
VERIFY_NOT_REACHED();
}
// Handle X alignment:
if (svg_box_state.has_definite_width()) {
switch (preserve_aspect_ratio.align) {
case SVG::PreserveAspectRatio::Align::xMinYMin:
case SVG::PreserveAspectRatio::Align::xMinYMid:
case SVG::PreserveAspectRatio::Align::xMinYMax:
// Align the <min-x> of the element's ‘viewBox’ with the smallest X value of the SVG viewport.
viewbox_transform.offset.translate_by(0, 0);
break;
case SVG::PreserveAspectRatio::Align::None: {
// Do not force uniform scaling. Scale the graphic content of the given element non-uniformly
// if necessary such that the element's bounding box exactly matches the SVG viewport rectangle.
// FIXME: None is unimplemented (treat as xMidYMid)
[[fallthrough]];
}
case SVG::PreserveAspectRatio::Align::xMidYMin:
case SVG::PreserveAspectRatio::Align::xMidYMid:
case SVG::PreserveAspectRatio::Align::xMidYMax:
// Align the midpoint X value of the element's ‘viewBox’ with the midpoint X value of the SVG viewport.
viewbox_transform.offset.translate_by((svg_box_state.content_width() - CSSPixels::nearest_value_for(view_box.width * viewbox_transform.scale_factor)) / 2, 0);
break;
case SVG::PreserveAspectRatio::Align::xMaxYMin:
case SVG::PreserveAspectRatio::Align::xMaxYMid:
case SVG::PreserveAspectRatio::Align::xMaxYMax:
// Align the <min-x>+<width> of the element's ‘viewBox’ with the maximum X value of the SVG viewport.
viewbox_transform.offset.translate_by((svg_box_state.content_width() - CSSPixels::nearest_value_for(view_box.width * viewbox_transform.scale_factor)), 0);
break;
default:
VERIFY_NOT_REACHED();
}
}
if (svg_box_state.has_definite_width()) {
switch (preserve_aspect_ratio.align) {
case SVG::PreserveAspectRatio::Align::xMinYMin:
case SVG::PreserveAspectRatio::Align::xMidYMin:
case SVG::PreserveAspectRatio::Align::xMaxYMin:
// Align the <min-y> of the element's ‘viewBox’ with the smallest Y value of the SVG viewport.
viewbox_transform.offset.translate_by(0, 0);
break;
case SVG::PreserveAspectRatio::Align::None: {
// Do not force uniform scaling. Scale the graphic content of the given element non-uniformly
// if necessary such that the element's bounding box exactly matches the SVG viewport rectangle.
// FIXME: None is unimplemented (treat as xMidYMid)
[[fallthrough]];
}
case SVG::PreserveAspectRatio::Align::xMinYMid:
case SVG::PreserveAspectRatio::Align::xMidYMid:
case SVG::PreserveAspectRatio::Align::xMaxYMid:
// Align the midpoint Y value of the element's ‘viewBox’ with the midpoint Y value of the SVG viewport.
viewbox_transform.offset.translate_by(0, (svg_box_state.content_height() - CSSPixels::nearest_value_for(view_box.height * viewbox_transform.scale_factor)) / 2);
break;
case SVG::PreserveAspectRatio::Align::xMinYMax:
case SVG::PreserveAspectRatio::Align::xMidYMax:
case SVG::PreserveAspectRatio::Align::xMaxYMax:
// Align the <min-y>+<height> of the element's ‘viewBox’ with the maximum Y value of the SVG viewport.
viewbox_transform.offset.translate_by(0, (svg_box_state.content_height() - CSSPixels::nearest_value_for(view_box.height * viewbox_transform.scale_factor)));
break;
default:
VERIFY_NOT_REACHED();
}
}
return viewbox_transform;
}
static bool should_ensure_creation_of_paintable(Node const& node)
{
if (is<SVGTextBox>(node))
return true;
if (is<SVGGraphicsBox>(node))
return true;
if (node.dom_node()) {
if (is<SVG::SVGUseElement>(*node.dom_node()))
return true;
if (is<SVG::SVGSymbolElement>(*node.dom_node()))
return true;
}
return false;
}
void SVGFormattingContext::run(Box const& box, LayoutMode layout_mode, AvailableSpace const& available_space)
{
auto& svg_svg_element = verify_cast<SVG::SVGSVGElement>(*box.dom_node());
auto svg_box_state = m_state.get(box);
auto root_offset = svg_box_state.offset;
box.for_each_child_of_type<BlockContainer>([&](BlockContainer const& child_box) {
if (is<SVG::SVGForeignObjectElement>(child_box.dom_node())) {
Layout::BlockFormattingContext bfc(m_state, child_box, this);
bfc.run(child_box, LayoutMode::Normal, available_space);
auto& child_state = m_state.get_mutable(child_box);
child_state.set_content_offset(child_state.offset.translated(root_offset));
}
return IterationDecision::Continue;
});
box.for_each_in_subtree([&](Node const& descendant) {
if (is<SVGGeometryBox>(descendant)) {
auto const& geometry_box = static_cast<SVGGeometryBox const&>(descendant);
auto& geometry_box_state = m_state.get_mutable(geometry_box);
auto& dom_node = const_cast<SVGGeometryBox&>(geometry_box).dom_node();
auto& path = dom_node.get_path();
auto svg_transform = dom_node.get_transform();
Gfx::AffineTransform viewbox_transform;
double viewbox_scale = 1;
auto maybe_view_box = dom_node.view_box();
if (maybe_view_box.has_value()) {
// FIXME: This should allow just one of width or height to be specified.
// E.g. We should be able to layout <svg width="100%"> where height is unspecified/auto.
if (!svg_box_state.has_definite_width() || !svg_box_state.has_definite_height()) {
dbgln_if(LIBWEB_CSS_DEBUG, "FIXME: Attempting to layout indefinitely sized SVG with a viewbox -- this likely won't work!");
}
auto view_box = maybe_view_box.value();
auto scale_width = svg_box_state.has_definite_width() ? svg_box_state.content_width() / view_box.width : 1;
auto scale_height = svg_box_state.has_definite_height() ? svg_box_state.content_height() / view_box.height : 1;
// The initial value for preserveAspectRatio is xMidYMid meet.
auto preserve_aspect_ratio = svg_svg_element.preserve_aspect_ratio().value_or(SVG::PreserveAspectRatio {});
auto viewbox_offset_and_scale = scale_and_align_viewbox_content(preserve_aspect_ratio, view_box, { scale_width, scale_height }, svg_box_state);
viewbox_transform = Gfx::AffineTransform {}.translate(viewbox_offset_and_scale.offset.to_type<float>()).scale(viewbox_offset_and_scale.scale_factor, viewbox_offset_and_scale.scale_factor).translate({ -view_box.min_x, -view_box.min_y });
viewbox_scale = viewbox_offset_and_scale.scale_factor;
}
// Stroke increases the path's size by stroke_width/2 per side.
auto path_transform = Gfx::AffineTransform {}.multiply(viewbox_transform).multiply(svg_transform);
auto path_bounding_box = path_transform.map(path.bounding_box()).to_type<CSSPixels>();
CSSPixels stroke_width = CSSPixels::nearest_value_for(static_cast<double>(geometry_box.dom_node().visible_stroke_width()) * viewbox_scale);
path_bounding_box.inflate(stroke_width, stroke_width);
geometry_box_state.set_content_offset(path_bounding_box.top_left());
geometry_box_state.set_content_width(path_bounding_box.width());
geometry_box_state.set_content_height(path_bounding_box.height());
geometry_box_state.set_svg_path_data(Painting::SVGGeometryPaintable::PathData(path, viewbox_transform, svg_transform));
} else if (is<SVGSVGBox>(descendant)) {
SVGFormattingContext nested_context(m_state, static_cast<SVGSVGBox const&>(descendant), this);
nested_context.run(static_cast<SVGSVGBox const&>(descendant), layout_mode, available_space);
} else if (should_ensure_creation_of_paintable(descendant)) {
// NOTE: This hack creates a layout state to ensure the existence of
// a paintable in LayoutState::commit().
m_state.get_mutable(static_cast<NodeWithStyleAndBoxModelMetrics const&>(descendant));
}
return IterationDecision::Continue;
});
// https://svgwg.org/svg2-draft/struct.html#Groups
// 5.2. Grouping: the ‘g’ element
// The ‘g’ element is a container element for grouping together related graphics elements.
box.for_each_in_subtree_of_type<Box>([&](Box const& descendant) {
if (is<SVGGraphicsBox>(descendant) && !is<SVGGeometryBox>(descendant) && !is<SVGTextBox>(descendant)) {
auto const& svg_graphics_box = static_cast<SVGGraphicsBox const&>(descendant);
auto& graphics_box_state = m_state.get_mutable(svg_graphics_box);
auto smallest_x_position = CSSPixels(0);
auto smallest_y_position = CSSPixels(0);
auto greatest_x_position = CSSPixels(0);
auto greatest_y_position = CSSPixels(0);
descendant.for_each_in_subtree_of_type<Box>([&](Box const& child_of_svg_container) {
auto& box_state = m_state.get_mutable(child_of_svg_container);
smallest_x_position = box_state.offset.x();
smallest_y_position = box_state.offset.y();
return IterationDecision::Break;
});
descendant.for_each_in_subtree_of_type<Box>([&](Box const& child_of_svg_container) {
auto& box_state = m_state.get_mutable(child_of_svg_container);
smallest_x_position = min(smallest_x_position, box_state.offset.x());
smallest_y_position = min(smallest_y_position, box_state.offset.y());
greatest_x_position = max(greatest_x_position, box_state.offset.x() + box_state.content_width());
greatest_y_position = max(greatest_y_position, box_state.offset.y() + box_state.content_height());
return IterationDecision::Continue;
});
graphics_box_state.set_content_x(smallest_x_position);
graphics_box_state.set_content_y(smallest_y_position);
graphics_box_state.set_content_width(greatest_x_position - smallest_x_position);
graphics_box_state.set_content_height(greatest_y_position - smallest_y_position);
}
return IterationDecision::Continue;
});
}
}
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