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

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

#include <LibGfx/AntiAliasingPainter.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/Layout/BlockContainer.h>
#include <LibWeb/Layout/ImageBox.h>
#include <LibWeb/Painting/BackgroundPainting.h>
#include <LibWeb/Painting/InlinePaintable.h>
#include <LibWeb/Painting/ShadowPainting.h>

namespace Web::Painting {

JS::NonnullGCPtr<InlinePaintable> InlinePaintable::create(Layout::InlineNode const& layout_node)
{
    return layout_node.heap().allocate_without_realm<InlinePaintable>(layout_node);
}

InlinePaintable::InlinePaintable(Layout::InlineNode const& layout_node)
    : Paintable(layout_node)
{
}

Layout::InlineNode const& InlinePaintable::layout_node() const
{
    return static_cast<Layout::InlineNode const&>(Paintable::layout_node());
}

void InlinePaintable::paint(PaintContext& context, PaintPhase phase) const
{
    auto& painter = context.painter();

    if (phase == PaintPhase::Background) {
        auto top_left_border_radius = computed_values().border_top_left_radius();
        auto top_right_border_radius = computed_values().border_top_right_radius();
        auto bottom_right_border_radius = computed_values().border_bottom_right_radius();
        auto bottom_left_border_radius = computed_values().border_bottom_left_radius();
        auto containing_block_position_in_absolute_coordinates = containing_block()->paintable_box()->absolute_position();

        for_each_fragment([&](auto const& fragment, bool is_first_fragment, bool is_last_fragment) {
            CSSPixelRect absolute_fragment_rect { containing_block_position_in_absolute_coordinates.translated(fragment.offset()), fragment.size() };

            if (is_first_fragment) {
                auto extra_start_width = box_model().padding.left;
                absolute_fragment_rect.translate_by(-extra_start_width, 0);
                absolute_fragment_rect.set_width(absolute_fragment_rect.width() + extra_start_width);
            }

            if (is_last_fragment) {
                auto extra_end_width = box_model().padding.right;
                absolute_fragment_rect.set_width(absolute_fragment_rect.width() + extra_end_width);
            }

            auto border_radii_data = normalized_border_radii_data(layout_node(), absolute_fragment_rect, top_left_border_radius, top_right_border_radius, bottom_right_border_radius, bottom_left_border_radius);
            paint_background(context, layout_node(), absolute_fragment_rect, computed_values().background_color(), computed_values().image_rendering(), &computed_values().background_layers(), border_radii_data);

            if (auto computed_box_shadow = computed_values().box_shadow(); !computed_box_shadow.is_empty()) {
                Vector<ShadowData> resolved_box_shadow_data;
                resolved_box_shadow_data.ensure_capacity(computed_box_shadow.size());
                for (auto const& layer : computed_box_shadow) {
                    resolved_box_shadow_data.empend(
                        layer.color,
                        layer.offset_x.to_px(layout_node()),
                        layer.offset_y.to_px(layout_node()),
                        layer.blur_radius.to_px(layout_node()),
                        layer.spread_distance.to_px(layout_node()),
                        layer.placement == CSS::ShadowPlacement::Outer ? ShadowPlacement::Outer : ShadowPlacement::Inner);
                }
                auto borders_data = BordersData {
                    .top = computed_values().border_top(),
                    .right = computed_values().border_right(),
                    .bottom = computed_values().border_bottom(),
                    .left = computed_values().border_left(),
                };
                auto absolute_fragment_rect_bordered = absolute_fragment_rect.inflated(
                    borders_data.top.width, borders_data.right.width,
                    borders_data.bottom.width, borders_data.left.width);
                paint_box_shadow(context, absolute_fragment_rect_bordered, absolute_fragment_rect,
                    borders_data, border_radii_data, resolved_box_shadow_data);
            }

            return IterationDecision::Continue;
        });
    }

    auto paint_border_or_outline = [&](Optional<BordersData> outline_data = {}, CSSPixels outline_offset = 0) {
        auto top_left_border_radius = computed_values().border_top_left_radius();
        auto top_right_border_radius = computed_values().border_top_right_radius();
        auto bottom_right_border_radius = computed_values().border_bottom_right_radius();
        auto bottom_left_border_radius = computed_values().border_bottom_left_radius();

        auto borders_data = BordersData {
            .top = computed_values().border_top(),
            .right = computed_values().border_right(),
            .bottom = computed_values().border_bottom(),
            .left = computed_values().border_left(),
        };

        auto containing_block_position_in_absolute_coordinates = containing_block()->paintable_box()->absolute_position();

        for_each_fragment([&](auto const& fragment, bool is_first_fragment, bool is_last_fragment) {
            CSSPixelRect absolute_fragment_rect { containing_block_position_in_absolute_coordinates.translated(fragment.offset()), fragment.size() };

            if (is_first_fragment) {
                auto extra_start_width = box_model().padding.left;
                absolute_fragment_rect.translate_by(-extra_start_width, 0);
                absolute_fragment_rect.set_width(absolute_fragment_rect.width() + extra_start_width);
            }

            if (is_last_fragment) {
                auto extra_end_width = box_model().padding.right;
                absolute_fragment_rect.set_width(absolute_fragment_rect.width() + extra_end_width);
            }

            auto borders_rect = absolute_fragment_rect.inflated(borders_data.top.width, borders_data.right.width, borders_data.bottom.width, borders_data.left.width);
            auto border_radii_data = normalized_border_radii_data(layout_node(), borders_rect, top_left_border_radius, top_right_border_radius, bottom_right_border_radius, bottom_left_border_radius);

            if (outline_data.has_value()) {
                auto outline_offset_x = outline_offset;
                auto outline_offset_y = outline_offset;
                // "Both the height and the width of the outside of the shape drawn by the outline should not
                // become smaller than twice the computed value of the outline-width property to make sure
                // that an outline can be rendered even with large negative values."
                // https://www.w3.org/TR/css-ui-4/#outline-offset
                // So, if the horizontal outline offset is > half the borders_rect's width then we set it to that.
                // (And the same for y)
                if ((borders_rect.width() / 2) + outline_offset_x < 0)
                    outline_offset_x = -borders_rect.width() / 2;
                if ((borders_rect.height() / 2) + outline_offset_y < 0)
                    outline_offset_y = -borders_rect.height() / 2;

                border_radii_data.inflate(outline_data->top.width + outline_offset_y, outline_data->right.width + outline_offset_x, outline_data->bottom.width + outline_offset_y, outline_data->left.width + outline_offset_x);
                borders_rect.inflate(outline_data->top.width + outline_offset_y, outline_data->right.width + outline_offset_x, outline_data->bottom.width + outline_offset_y, outline_data->left.width + outline_offset_x);
                paint_all_borders(context.painter(), context.rounded_device_rect(borders_rect), border_radii_data.as_corners(context), outline_data->to_device_pixels(context));
            } else {
                paint_all_borders(context.painter(), context.rounded_device_rect(borders_rect), border_radii_data.as_corners(context), borders_data.to_device_pixels(context));
            }

            return IterationDecision::Continue;
        });
    };

    if (phase == PaintPhase::Border) {
        paint_border_or_outline();
    }

    if (phase == PaintPhase::Outline) {
        auto outline_width = computed_values().outline_width().to_px(layout_node());
        auto maybe_outline_data = borders_data_for_outline(layout_node(), computed_values().outline_color(), computed_values().outline_style(), outline_width);
        if (maybe_outline_data.has_value()) {
            paint_border_or_outline(maybe_outline_data.value(), computed_values().outline_offset().to_px(layout_node()));
        }
    }

    if (phase == PaintPhase::Overlay && layout_node().document().inspected_layout_node() == &layout_node()) {
        // FIXME: This paints a double-thick border between adjacent fragments, where ideally there
        //        would be none. Once we implement non-rectangular outlines for the `outline` CSS
        //        property, we can use that here instead.
        for_each_fragment([&](auto const& fragment, bool, bool) {
            painter.draw_rect(context.enclosing_device_rect(fragment.absolute_rect()).template to_type<int>(), Color::Magenta);
            return IterationDecision::Continue;
        });
    }
}

template<typename Callback>
void InlinePaintable::for_each_fragment(Callback callback) const
{
    // FIXME: This will be slow if the containing block has a lot of fragments!
    Vector<Layout::LineBoxFragment const&> fragments;
    verify_cast<PaintableWithLines>(*containing_block()->paintable_box()).for_each_fragment([&](auto& fragment) {
        if (layout_node().is_inclusive_ancestor_of(fragment.layout_node()))
            fragments.append(fragment);
        return IterationDecision::Continue;
    });
    for (size_t i = 0; i < fragments.size(); ++i) {
        auto const& fragment = fragments[i];
        callback(fragment, i == 0, i == fragments.size() - 1);
    }
}

}