serenity/Userland/Libraries/LibWeb/Painting/SVGPathPaintable.cpp

/*
 * Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
 * Copyright (c) 2023, MacDue <macdue@dueutil.tech>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibGfx/AntiAliasingPainter.h>
#include <LibWeb/Painting/SVGPathPaintable.h>
#include <LibWeb/SVG/SVGSVGElement.h>

namespace Web::Painting {

JS::NonnullGCPtr<SVGPathPaintable> SVGPathPaintable::create(Layout::SVGGraphicsBox const& layout_box)
{
    return layout_box.heap().allocate_without_realm<SVGPathPaintable>(layout_box);
}

SVGPathPaintable::SVGPathPaintable(Layout::SVGGraphicsBox const& layout_box)
    : SVGGraphicsPaintable(layout_box)
{
}

Layout::SVGGraphicsBox const& SVGPathPaintable::layout_box() const
{
    return static_cast<Layout::SVGGraphicsBox const&>(layout_node());
}

Optional<HitTestResult> SVGPathPaintable::hit_test(CSSPixelPoint position, HitTestType type) const
{
    auto result = SVGGraphicsPaintable::hit_test(position, type);
    if (!result.has_value() || !computed_path().has_value())
        return {};
    auto transformed_bounding_box = computed_transforms().svg_to_css_pixels_transform().map_to_quad(computed_path()->bounding_box());
    if (!transformed_bounding_box.contains(position.to_type<float>()))
        return {};
    return result;
}

static Gfx::Painter::WindingRule to_gfx_winding_rule(SVG::FillRule fill_rule)
{
    switch (fill_rule) {
    case SVG::FillRule::Nonzero:
        return Gfx::Painter::WindingRule::Nonzero;
    case SVG::FillRule::Evenodd:
        return Gfx::Painter::WindingRule::EvenOdd;
    default:
        VERIFY_NOT_REACHED();
    }
}

void SVGPathPaintable::paint(PaintContext& context, PaintPhase phase) const
{
    if (!is_visible() || !computed_path().has_value())
        return;

    SVGGraphicsPaintable::paint(context, phase);

    if (phase != PaintPhase::Foreground)
        return;

    auto& geometry_element = layout_box().dom_node();

    auto const* svg_element = geometry_element.shadow_including_first_ancestor_of_type<SVG::SVGSVGElement>();
    auto svg_element_rect = svg_element->paintable_box()->absolute_rect();

    // FIXME: This should not be trucated to an int.
    RecordingPainterStateSaver save_painter { context.recording_painter() };

    auto offset = context.floored_device_point(svg_element_rect.location()).to_type<int>().to_type<float>();
    auto maybe_view_box = geometry_element.view_box();

    auto paint_transform = computed_transforms().svg_to_device_pixels_transform(context);
    Gfx::Path path = computed_path()->copy_transformed(paint_transform);

    // Fills are computed as though all subpaths are closed (https://svgwg.org/svg2-draft/painting.html#FillProperties)
    auto closed_path = [&] {
        // We need to fill the path before applying the stroke, however the filled
        // path must be closed, whereas the stroke path may not necessary be closed.
        // Copy the path and close it for filling, but use the previous path for stroke
        auto copy = path;
        copy.close_all_subpaths();
        return copy;
    };

    // Note: This is assuming .x_scale() == .y_scale() (which it does currently).
    auto viewbox_scale = paint_transform.x_scale();

    auto svg_viewport = [&] {
        if (maybe_view_box.has_value())
            return Gfx::FloatRect { maybe_view_box->min_x, maybe_view_box->min_y, maybe_view_box->width, maybe_view_box->height };
        return Gfx::FloatRect { { 0, 0 }, svg_element_rect.size().to_type<float>() };
    }();

    SVG::SVGPaintContext paint_context {
        .viewport = svg_viewport,
        .path_bounding_box = computed_path()->bounding_box(),
        .transform = paint_transform
    };

    auto fill_opacity = geometry_element.fill_opacity().value_or(1);
    auto winding_rule = to_gfx_winding_rule(geometry_element.fill_rule().value_or(SVG::FillRule::Nonzero));
    if (auto paint_style = geometry_element.fill_paint_style(paint_context); paint_style.has_value()) {
        context.recording_painter().fill_path({
            .path = closed_path(),
            .paint_style = *paint_style,
            .winding_rule = winding_rule,
            .opacity = fill_opacity,
            .translation = offset,
        });
    } else if (auto fill_color = geometry_element.fill_color(); fill_color.has_value()) {
        context.recording_painter().fill_path({
            .path = closed_path(),
            .color = fill_color->with_opacity(fill_opacity),
            .winding_rule = winding_rule,
            .translation = offset,
        });
    }

    auto stroke_opacity = geometry_element.stroke_opacity().value_or(1);

    // Note: This is assuming .x_scale() == .y_scale() (which it does currently).
    float stroke_thickness = geometry_element.stroke_width().value_or(1) * viewbox_scale;

    if (auto paint_style = geometry_element.stroke_paint_style(paint_context); paint_style.has_value()) {
        context.recording_painter().stroke_path({
            .path = path,
            .paint_style = *paint_style,
            .thickness = stroke_thickness,
            .opacity = stroke_opacity,
            .translation = offset,
        });
    } else if (auto stroke_color = geometry_element.stroke_color(); stroke_color.has_value()) {
        context.recording_painter().stroke_path({
            .path = path,
            .color = stroke_color->with_opacity(stroke_opacity),
            .thickness = stroke_thickness,
            .translation = offset,
        });
    }
}

}