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serenity/Userland/Libraries/LibWeb/Layout/SVGFormattingContext.cpp
MacDue 5cf1570f40 LibWeb: Add initial support for nesting SVG viewports 
Previously, we were handling viewBoxes/viewports in a slightly hacky
way, asking graphics elements to figure out what viewBox to use during
layout. This does not work in all cases, and can't allow for more
complex SVGs where it is possible to have nested viewports.

This commit makes the SVGFormattingContext keep track of the
viewport/boxes, and it now lays out each viewport recursively, where
each nested `<svg>` or `<symbol>` can establish a new viewport.

This fixes some previous edge cases, and starts to allow nested
viewports (there's still some issues to resolve there).

Fixes #22931
2024-01-27 18:12:13 +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 <LibGfx/BoundingBox.h>
#include <LibGfx/Font/ScaledFont.h>
#include <LibGfx/TextLayout.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/Layout/SVGTextPathBox.h>
#include <LibWeb/SVG/SVGForeignObjectElement.h>
#include <LibWeb/SVG/SVGGElement.h>
#include <LibWeb/SVG/SVGMaskElement.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, Gfx::AffineTransform parent_viewbox_transform)
: FormattingContext(Type::SVG, state, box, parent)
, m_parent_viewbox_transform(parent_viewbox_transform)
{
}
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 is_container_element(Node const& node)
{
// https://svgwg.org/svg2-draft/struct.html#GroupsOverview
auto* dom_node = node.dom_node();
if (!dom_node)
return false;
if (is<SVG::SVGUseElement>(dom_node))
return true;
if (is<SVG::SVGSymbolElement>(dom_node))
return true;
if (is<SVG::SVGGElement>(dom_node))
return true;
if (is<SVG::SVGMaskElement>(dom_node))
return true;
return false;
}
enum class TraversalDecision {
Continue,
SkipChildrenAndContinue,
Break,
};
// FIXME: Add TraversalDecision::SkipChildrenAndContinue to TreeNode's implementation.
template<typename Callback>
static TraversalDecision for_each_in_inclusive_subtree(Layout::Node const& node, Callback callback)
{
if (auto decision = callback(node); decision != TraversalDecision::Continue)
return decision;
for (auto* child = node.first_child(); child; child = child->next_sibling()) {
if (for_each_in_inclusive_subtree(*child, callback) == TraversalDecision::Break)
return TraversalDecision::Break;
}
return TraversalDecision::Continue;
}
// FIXME: Add TraversalDecision::SkipChildrenAndContinue to TreeNode's implementation.
template<typename Callback>
static TraversalDecision for_each_in_subtree(Layout::Node const& node, Callback callback)
{
for (auto* child = node.first_child(); child; child = child->next_sibling()) {
if (for_each_in_inclusive_subtree(*child, callback) == TraversalDecision::Break)
return TraversalDecision::Break;
}
return TraversalDecision::Continue;
}
void SVGFormattingContext::run(Box const& box, LayoutMode layout_mode, AvailableSpace const& available_space)
{
auto& svg_viewport = dynamic_cast<SVG::SVGViewport const&>(*box.dom_node());
auto& svg_box_state = m_state.get_mutable(box);
auto viewbox = svg_viewport.view_box();
// https://svgwg.org/svg2-draft/coords.html#ViewBoxAttribute
if (viewbox.has_value()) {
if (viewbox->width < 0 || viewbox->height < 0) {
// A negative value for <width> or <height> is an error and invalidates the ‘viewBox’ attribute.
viewbox = {};
} else if (viewbox->width == 0 || viewbox->height == 0) {
// A value of zero disables rendering of the element.
return;
}
}
auto viewbox_transform = [&] {
if (!viewbox.has_value())
return m_parent_viewbox_transform;
// 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 scale_width = svg_box_state.has_definite_width() ? svg_box_state.content_width() / viewbox->width : 1;
auto scale_height = svg_box_state.has_definite_height() ? svg_box_state.content_height() / viewbox->height : 1;
// The initial value for preserveAspectRatio is xMidYMid meet.
auto preserve_aspect_ratio = svg_viewport.preserve_aspect_ratio().value_or(SVG::PreserveAspectRatio {});
auto viewbox_offset_and_scale = scale_and_align_viewbox_content(preserve_aspect_ratio, *viewbox, { scale_width, scale_height }, svg_box_state);
CSSPixelPoint offset = viewbox_offset_and_scale.offset;
return Gfx::AffineTransform { m_parent_viewbox_transform }.multiply(Gfx::AffineTransform {}
.translate(offset.to_type<float>())
.scale(viewbox_offset_and_scale.scale_factor, viewbox_offset_and_scale.scale_factor)
.translate({ -viewbox->min_x, -viewbox->min_y }));
}();
if (svg_box_state.has_definite_width() && svg_box_state.has_definite_height()) {
// Scale the box of the viewport based on the parent's viewBox transform.
// The viewBox transform is always just a simple scale + offset.
// FIXME: Avoid converting SVG box to floats.
Gfx::FloatRect svg_rect = { svg_box_state.offset.to_type<float>(),
{ float(svg_box_state.content_width()), float(svg_box_state.content_height()) } };
svg_rect = m_parent_viewbox_transform.map(svg_rect);
svg_box_state.set_content_offset(svg_rect.location().to_type<CSSPixels>());
svg_box_state.set_content_width(CSSPixels(svg_rect.width()));
svg_box_state.set_content_height(CSSPixels(svg_rect.height()));
}
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;
});
for_each_in_subtree(box, [&](Node const& descendant) {
if (is<SVG::SVGViewport>(descendant.dom_node())) {
// Layout for a nested SVG viewport.
// https://svgwg.org/svg2-draft/coords.html#EstablishingANewSVGViewport.
SVGFormattingContext nested_context(m_state, static_cast<Box const&>(descendant), this, viewbox_transform);
auto& nested_viewport_state = m_state.get_mutable(static_cast<Box const&>(descendant));
auto viewport_width = [&] {
if (viewbox.has_value())
return CSSPixels::nearest_value_for(viewbox->width);
if (svg_box_state.has_definite_width())
return svg_box_state.content_width();
dbgln_if(LIBWEB_CSS_DEBUG, "FIXME: Failed to resolve width of SVG viewport!");
return CSSPixels {};
}();
auto viewport_height = [&] {
if (viewbox.has_value())
return CSSPixels::nearest_value_for(viewbox->height);
if (svg_box_state.has_definite_height())
return svg_box_state.content_height();
dbgln_if(LIBWEB_CSS_DEBUG, "FIXME: Failed to resolve height of SVG viewport!");
return CSSPixels {};
}();
auto resolve_dimension = [](auto& node, auto size, auto reference_value) {
// The value auto for width and height on the ‘svg’ element is treated as 100%.
// https://svgwg.org/svg2-draft/geometry.html#Sizing
if (size.is_auto())
return reference_value;
return size.to_px(node, reference_value);
};
// FIXME: Support the x/y attributes to calculate the offset.
auto nested_viewport_width = resolve_dimension(descendant, descendant.computed_values().width(), viewport_width);
auto nested_viewport_height = resolve_dimension(descendant, descendant.computed_values().height(), viewport_height);
nested_viewport_state.set_content_width(nested_viewport_width);
nested_viewport_state.set_content_height(nested_viewport_height);
nested_context.run(static_cast<Box const&>(descendant), layout_mode, available_space);
return TraversalDecision::SkipChildrenAndContinue;
}
if (is<SVGGraphicsBox>(descendant)) {
auto const& graphics_box = static_cast<SVGGraphicsBox const&>(descendant);
auto& dom_node = const_cast<SVGGraphicsBox&>(graphics_box).dom_node();
auto& graphics_box_state = m_state.get_mutable(graphics_box);
auto svg_transform = dom_node.get_transform();
graphics_box_state.set_computed_svg_transforms(Painting::SVGGraphicsPaintable::ComputedTransforms(viewbox_transform, svg_transform));
auto to_css_pixels_transform = Gfx::AffineTransform {}.multiply(viewbox_transform).multiply(svg_transform);
Gfx::Path path;
if (is<SVGGeometryBox>(descendant)) {
path = static_cast<SVG::SVGGeometryElement&>(dom_node).get_path();
} else if (is<SVGTextBox>(descendant)) {
auto& text_element = static_cast<SVG::SVGTextPositioningElement&>(dom_node);
auto& font = graphics_box.first_available_font();
auto text_contents = text_element.text_contents();
Utf8View text_utf8 { text_contents };
auto text_width = font.width(text_utf8);
auto text_offset = text_element.get_offset();
// https://svgwg.org/svg2-draft/text.html#TextAnchoringProperties
switch (text_element.text_anchor().value_or(SVG::TextAnchor::Start)) {
case SVG::TextAnchor::Start:
// The rendered characters are aligned such that the start of the resulting rendered text is at the initial
// current text position.
break;
case SVG::TextAnchor::Middle: {
// The rendered characters are shifted such that the geometric middle of the resulting rendered text
// (determined from the initial and final current text position before applying the text-anchor property)
// is at the initial current text position.
text_offset.translate_by(-text_width / 2, 0);
break;
}
case SVG::TextAnchor::End: {
// The rendered characters are shifted such that the end of the resulting rendered text (final current text
// position before applying the text-anchor property) is at the initial current text position.
text_offset.translate_by(-text_width, 0);
break;
}
default:
VERIFY_NOT_REACHED();
}
path.move_to(text_offset);
path.text(text_utf8, font);
} else if (is<SVGTextPathBox>(descendant)) {
auto& text_path_element = static_cast<SVG::SVGTextPathElement&>(dom_node);
auto path_or_shape = text_path_element.path_or_shape();
if (!path_or_shape)
return TraversalDecision::Continue;
auto& font = graphics_box.first_available_font();
auto text_contents = text_path_element.text_contents();
Utf8View text_utf8 { text_contents };
auto shape_path = const_cast<SVG::SVGGeometryElement&>(*path_or_shape).get_path();
path = shape_path.place_text_along(text_utf8, font);
}
auto path_bounding_box = to_css_pixels_transform.map(path.bounding_box()).to_type<CSSPixels>();
// Stroke increases the path's size by stroke_width/2 per side.
CSSPixels stroke_width = CSSPixels::nearest_value_for(graphics_box.dom_node().visible_stroke_width() * viewbox_transform.x_scale());
path_bounding_box.inflate(stroke_width, stroke_width);
graphics_box_state.set_content_offset(path_bounding_box.top_left());
graphics_box_state.set_content_width(path_bounding_box.width());
graphics_box_state.set_content_height(path_bounding_box.height());
graphics_box_state.set_computed_svg_path(move(path));
}
return TraversalDecision::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_container_element(descendant)) {
Gfx::BoundingBox<CSSPixels> bounding_box;
descendant.for_each_in_subtree_of_type<Box>([&](Box const& child_of_svg_container) {
auto& box_state = m_state.get(child_of_svg_container);
bounding_box.add_point(box_state.offset);
bounding_box.add_point(box_state.offset.translated(box_state.content_width(), box_state.content_height()));
return IterationDecision::Continue;
});
auto& box_state = m_state.get_mutable(descendant);
box_state.set_content_x(bounding_box.x());
box_state.set_content_y(bounding_box.y());
box_state.set_content_width(bounding_box.width());
box_state.set_content_height(bounding_box.height());
}
return IterationDecision::Continue;
});
}
}
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