/*

 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <AK/Enumerate.h>

#include <AK/Math.h>

#include <AK/StringBuilder.h>

#include <AK/TypeCasts.h>

#include <LibGfx/BoundingBox.h>

#include <LibGfx/Font/ScaledFont.h>

#include <LibGfx/Painter.h>

#include <LibGfx/Path.h>

#include <LibGfx/TextLayout.h>

#include <LibGfx/Vector2.h>

namespace Gfx {

void Path::approximate_elliptical_arc_with_cubic_beziers(FloatPoint center, FloatSize radii, float x_axis_rotation, float theta, float theta_delta)

{

    float sin_x_rotation;

    float cos_x_rotation;

    AK::sincos(x_axis_rotation, sin_x_rotation, cos_x_rotation);

    auto arc_point_and_derivative = [&](float t, FloatPoint& point, FloatPoint& derivative) {

        float sin_angle;

        float cos_angle;

        AK::sincos(t, sin_angle, cos_angle);

        point = FloatPoint {

            center.x()

                + radii.width() * cos_x_rotation * cos_angle

                - radii.height() * sin_x_rotation * sin_angle,

            center.y()

                + radii.width() * sin_x_rotation * cos_angle

                + radii.height() * cos_x_rotation * sin_angle,

        };

        derivative = FloatPoint {

            -radii.width() * cos_x_rotation * sin_angle

                - radii.height() * sin_x_rotation * cos_angle,

            -radii.width() * sin_x_rotation * sin_angle

                + radii.height() * cos_x_rotation * cos_angle,

        };

    };

    auto approximate_arc_between = [&](float start_angle, float end_angle) {

        auto t = AK::tan((end_angle - start_angle) / 2);

        auto alpha = AK::sin(end_angle - start_angle) * ((AK::sqrt(4 + 3 * t * t) - 1) / 3);

        FloatPoint p1, d1;

        FloatPoint p2, d2;

        arc_point_and_derivative(start_angle, p1, d1);

        arc_point_and_derivative(end_angle, p2, d2);

        auto q1 = p1 + d1.scaled(alpha, alpha);

        auto q2 = p2 - d2.scaled(alpha, alpha);

        cubic_bezier_curve_to(q1, q2, p2);

    };

    // FIXME: Come up with a more mathematically sound step size (using some error calculation).

    auto step = theta_delta;

    int step_count = 1;

    while (fabs(step) > AK::Pi<float> / 4) {

        step /= 2;

        step_count *= 2;

    }

    float prev = theta;

    float t = prev + step;

    for (int i = 0; i < step_count; i++, prev = t, t += step)

        approximate_arc_between(prev, t);

}

void Path::elliptical_arc_to(FloatPoint point, FloatSize radii, float x_axis_rotation, bool large_arc, bool sweep)

{

    auto next_point = point;

    double rx = radii.width();

    double ry = radii.height();

    double x_axis_rotation_s;

    double x_axis_rotation_c;

    AK::sincos(static_cast<double>(x_axis_rotation), x_axis_rotation_s, x_axis_rotation_c);

    FloatPoint last_point = this->last_point();

    // Step 1 of out-of-range radii correction

    if (rx == 0.0 || ry == 0.0) {

        append_segment<PathSegment::LineTo>(next_point);

        return;

    }

    // Step 2 of out-of-range radii correction

    if (rx < 0)

        rx *= -1.0;

    if (ry < 0)

        ry *= -1.0;

    // POSSIBLY HACK: Handle the case where both points are the same.

    auto same_endpoints = next_point == last_point;

    if (same_endpoints) {

        if (!large_arc) {

            // Nothing is going to be drawn anyway.

            return;

        }

        // Move the endpoint by a small amount to avoid division by zero.

        next_point.translate_by(0.01f, 0.01f);

    }

    // Find (cx, cy), theta_1, theta_delta

    // Step 1: Compute (x1', y1')

    auto x_avg = static_cast<double>(last_point.x() - next_point.x()) / 2.0;

    auto y_avg = static_cast<double>(last_point.y() - next_point.y()) / 2.0;

    auto x1p = x_axis_rotation_c * x_avg + x_axis_rotation_s * y_avg;

    auto y1p = -x_axis_rotation_s * x_avg + x_axis_rotation_c * y_avg;

    // Step 2: Compute (cx', cy')

    double x1p_sq = x1p * x1p;

    double y1p_sq = y1p * y1p;

    double rx_sq = rx * rx;

    double ry_sq = ry * ry;

    // Step 3 of out-of-range radii correction

    double lambda = x1p_sq / rx_sq + y1p_sq / ry_sq;

    double multiplier;

    if (lambda > 1.0) {

        auto lambda_sqrt = AK::sqrt(lambda);

        rx *= lambda_sqrt;

        ry *= lambda_sqrt;

        multiplier = 0.0;

    } else {

        double numerator = rx_sq * ry_sq - rx_sq * y1p_sq - ry_sq * x1p_sq;

        double denominator = rx_sq * y1p_sq + ry_sq * x1p_sq;

        multiplier = AK::sqrt(AK::max(0., numerator) / denominator);

    }

    if (large_arc == sweep)

        multiplier *= -1.0;

    double cxp = multiplier * rx * y1p / ry;

    double cyp = multiplier * -ry * x1p / rx;

    // Step 3: Compute (cx, cy) from (cx', cy')

    x_avg = (last_point.x() + next_point.x()) / 2.0f;

    y_avg = (last_point.y() + next_point.y()) / 2.0f;

    double cx = x_axis_rotation_c * cxp - x_axis_rotation_s * cyp + x_avg;

    double cy = x_axis_rotation_s * cxp + x_axis_rotation_c * cyp + y_avg;

    double theta_1 = AK::atan2((y1p - cyp) / ry, (x1p - cxp) / rx);

    double theta_2 = AK::atan2((-y1p - cyp) / ry, (-x1p - cxp) / rx);

    auto theta_delta = theta_2 - theta_1;

    if (!sweep && theta_delta > 0.0) {

        theta_delta -= 2 * AK::Pi<double>;

    } else if (sweep && theta_delta < 0) {

        theta_delta += 2 * AK::Pi<double>;

    }

    approximate_elliptical_arc_with_cubic_beziers(

        { cx, cy },

        { rx, ry },

        x_axis_rotation,

        theta_1,

        theta_delta);

}

void Path::quad(FloatQuad const& quad)

{

    move_to(quad.p1());

    line_to(quad.p2());

    line_to(quad.p3());

    line_to(quad.p4());

    close();

}

void Path::rounded_rect(FloatRect const& rect, CornerRadius top_left, CornerRadius top_right, CornerRadius bottom_right, CornerRadius bottom_left)

{

    auto x = rect.x();

    auto y = rect.y();

    auto width = rect.width();

    auto height = rect.height();

    if (top_left)

        move_to({ x + top_left.horizontal_radius, y });

    else

        move_to({ x, y });

    if (top_right) {

        horizontal_line_to(x + width - top_right.horizontal_radius);

        elliptical_arc_to({ x + width, y + top_right.horizontal_radius }, { top_right.horizontal_radius, top_right.vertical_radius }, 0, false, true);

    } else {

        horizontal_line_to(x + width);

    }

    if (bottom_right) {

        vertical_line_to(y + height - bottom_right.vertical_radius);

        elliptical_arc_to({ x + width - bottom_right.horizontal_radius, y + height }, { bottom_right.horizontal_radius, bottom_right.vertical_radius }, 0, false, true);

    } else {

        vertical_line_to(y + height);

    }

    if (bottom_left) {

        horizontal_line_to(x + bottom_left.horizontal_radius);

        elliptical_arc_to({ x, y + height - bottom_left.vertical_radius }, { bottom_left.horizontal_radius, bottom_left.vertical_radius }, 0, false, true);

    } else {

        horizontal_line_to(x);

    }

    if (top_left) {

        vertical_line_to(y + top_left.vertical_radius);

        elliptical_arc_to({ x + top_left.horizontal_radius, y }, { top_left.horizontal_radius, top_left.vertical_radius }, 0, false, true);

    } else {

        vertical_line_to(y);

    }

}

void Path::text(Utf8View text, Font const& font)

{

    if (!is<ScaledFont>(font)) {

        // FIXME: This API only accepts Gfx::Font for ease of use.

        dbgln("Cannot path-ify bitmap fonts!");

        return;

    }

    auto& scaled_font = static_cast<ScaledFont const&>(font);

    for_each_glyph_position(

        last_point(), text, scaled_font, [&](DrawGlyphOrEmoji glyph_or_emoji) {

            if (glyph_or_emoji.has<DrawGlyph>()) {

                auto& glyph = glyph_or_emoji.get<DrawGlyph>();

                move_to(glyph.position);

                auto glyph_id = scaled_font.glyph_id_for_code_point(glyph.code_point);

                scaled_font.append_glyph_path_to(*this, glyph_id);

            }

        },

        IncludeLeftBearing::Yes);

}

Path Path::place_text_along(Utf8View text, Font const& font) const

{

    if (!is<ScaledFont>(font)) {

        // FIXME: This API only accepts Gfx::Font for ease of use.

        dbgln("Cannot path-ify bitmap fonts!");

        return {};

    }

    auto lines = split_lines();

    auto next_point_for_offset = [&, line_index = 0U, distance_along_path = 0.0f, last_line_length = 0.0f](float offset) mutable -> Optional<FloatPoint> {

        while (line_index < lines.size() && offset > distance_along_path) {

            last_line_length = lines[line_index++].length();

            distance_along_path += last_line_length;

        }

        if (offset > distance_along_path)

            return {};

        if (last_line_length > 1) {

            // If the last line segment was fairly long, compute the point in the line.

            float p = (last_line_length + offset - distance_along_path) / last_line_length;

            auto current_line = lines[line_index - 1];

            return current_line.a() + (current_line.b() - current_line.a()).scaled(p);

        }

        if (line_index >= lines.size())

            return {};

        return lines[line_index].a();

    };

    auto& scaled_font = static_cast<Gfx::ScaledFont const&>(font);

    Gfx::Path result_path;

    Gfx::for_each_glyph_position(

        {}, text, font, [&](Gfx::DrawGlyphOrEmoji glyph_or_emoji) {

            auto* glyph = glyph_or_emoji.get_pointer<Gfx::DrawGlyph>();

            if (!glyph)

                return;

            auto offset = glyph->position.x();

            auto width = font.glyph_width(glyph->code_point);

            auto start = next_point_for_offset(offset);

            if (!start.has_value())

                return;

            auto end = next_point_for_offset(offset + width);

            if (!end.has_value())

                return;

            // Find the angle between the start and end points on the path.

            auto delta = *end - *start;

            auto angle = AK::atan2(delta.y(), delta.x());

            Gfx::Path glyph_path;

            // Rotate the glyph then move it to start point.

            auto glyph_id = scaled_font.glyph_id_for_code_point(glyph->code_point);

            scaled_font.append_glyph_path_to(glyph_path, glyph_id);

            auto transform = Gfx::AffineTransform {}

                                 .translate(*start)

                                 .multiply(Gfx::AffineTransform {}.rotate_radians(angle))

                                 .multiply(Gfx::AffineTransform {}.translate({ 0, -scaled_font.pixel_metrics().ascent }));

            glyph_path = glyph_path.copy_transformed(transform);

            result_path.append_path(glyph_path);

        },

        Gfx::IncludeLeftBearing::Yes);

    return result_path;

}

void Path::close()

{

    // If there's no `moveto` starting this subpath assume the start is (0, 0).

    FloatPoint first_point_in_subpath = { 0, 0 };

    for (auto it = end(); it-- != begin();) {

        auto segment = *it;

        if (segment.command() == PathSegment::MoveTo) {

            first_point_in_subpath = segment.point();

            break;

        }

    }

    if (first_point_in_subpath != last_point())

        line_to(first_point_in_subpath);

    append_segment<PathSegment::ClosePath>();

}

void Path::close_all_subpaths()

{

    // This is only called before filling, not before stroking, so this doesn't have to insert ClosePath segments.

    auto it = begin();

    // Note: Get the end outside the loop as closing subpaths will move the end.

    auto end = this->end();

    while (it < end) {

        // If there's no `moveto` starting this subpath assume the start is (0, 0).

        FloatPoint first_point_in_subpath = { 0, 0 };

        auto segment = *it;

        if (segment.command() == PathSegment::MoveTo) {

            first_point_in_subpath = segment.point();

            ++it;

        }

        // Find the end of the current subpath.

        FloatPoint cursor = first_point_in_subpath;

        for (; it < end; ++it) {

            auto segment = *it;

            if (segment.command() == PathSegment::ClosePath)

                continue;

            if (segment.command() == PathSegment::MoveTo)

                break;

            cursor = segment.point();

        }

        // Close the subpath.

        if (first_point_in_subpath != cursor) {

            move_to(cursor);

            line_to(first_point_in_subpath);

        }

    }

}

ByteString Path::to_byte_string() const

{

    // Dumps this path as an SVG compatible string.

    StringBuilder builder;

    if (is_empty() || m_commands.first() != PathSegment::MoveTo)

        builder.append("M 0,0"sv);

    for (auto segment : *this) {

        if (!builder.is_empty())

            builder.append(' ');

        switch (segment.command()) {

        case PathSegment::MoveTo:

            builder.append('M');

            break;

        case PathSegment::LineTo:

            builder.append('L');

            break;

        case PathSegment::QuadraticBezierCurveTo:

            builder.append('Q');

            break;

        case PathSegment::CubicBezierCurveTo:

            builder.append('C');

            break;

        case PathSegment::ClosePath:

            builder.append('Z');

            break;

        }

        for (auto point : segment.points())

            builder.appendff(" {},{}", point.x(), point.y());

    }

    return builder.to_byte_string();

}

Optional<FloatRect> Path::as_rect() const

{

    if (m_commands.size() != 6 || m_points.size() != 5)

        return {};

    if (m_commands[0] != PathSegment::MoveTo

        || m_commands[1] != PathSegment::LineTo

        || m_commands[2] != PathSegment::LineTo

        || m_commands[3] != PathSegment::LineTo

        || m_commands[4] != PathSegment::LineTo

        || m_commands[5] != PathSegment::ClosePath)

        return {};

    VERIFY(m_points[0] == m_points[4]);

    if (m_points[0].y() != m_points[1].y()

        || m_points[1].x() != m_points[2].x()

        || m_points[2].y() != m_points[3].y()

        || m_points[3].x() != m_points[0].x())

        return {};

    return FloatRect::from_two_points(m_points[0], m_points[2]);

}

void Path::segmentize_path()

{

    Vector<FloatLine> segments;

    FloatBoundingBox bounding_box;

    Vector<size_t> subpath_end_indices;

    auto add_line = [&](auto const& p0, auto const& p1) {

        segments.append({ p0, p1 });

        bounding_box.add_point(p1);

    };

    FloatPoint cursor { 0, 0 };

    for (auto segment : *this) {

        switch (segment.command()) {

        case PathSegment::MoveTo:

            bounding_box.add_point(segment.point());

            break;

        case PathSegment::LineTo: {

            add_line(cursor, segment.point());

            break;

        }

        case PathSegment::QuadraticBezierCurveTo: {

            Painter::for_each_line_segment_on_bezier_curve(segment.through(), cursor, segment.point(), [&](FloatPoint p0, FloatPoint p1) {

                add_line(p0, p1);

            });

            break;

        }

        case PathSegment::CubicBezierCurveTo: {

            Painter::for_each_line_segment_on_cubic_bezier_curve(segment.through_0(), segment.through_1(), cursor, segment.point(), [&](FloatPoint p0, FloatPoint p1) {

                add_line(p0, p1);

            });

            break;

        }

        case PathSegment::ClosePath: {

            if (subpath_end_indices.is_empty() || subpath_end_indices.last() != segments.size() - 1)

                subpath_end_indices.append(segments.size() - 1);

            break;

        }

        }

        if (segment.command() != PathSegment::ClosePath)

            cursor = segment.point();

    }

    m_split_lines = SplitLines { move(segments), bounding_box, move(subpath_end_indices) };

}

Path Path::copy_transformed(Gfx::AffineTransform const& transform) const

{

    Path result;

    result.m_commands = m_commands;

    result.m_points.ensure_capacity(m_points.size());

    for (auto point : m_points)

        result.m_points.unchecked_append(transform.map(point));

    return result;

}

void Path::transform(AffineTransform const& transform)

{

    for (auto& point : m_points)

        point = transform.map(point);

    invalidate_split_lines();

}

void Path::append_path(Path const& path, AppendRelativeToLastPoint relative_to_last_point)

{

    auto previous_last_point = last_point();

    auto new_points_start = m_points.size();

    m_commands.extend(path.m_commands);

    m_points.extend(path.m_points);

    if (relative_to_last_point == AppendRelativeToLastPoint::Yes) {

        for (size_t i = new_points_start; i < m_points.size(); i++)

            m_points[i] += previous_last_point;

    }

    invalidate_split_lines();

}

template<typename T>

struct RoundTrip {

    RoundTrip(ReadonlySpan<T> span)

        : m_span(span)

    {

    }

    size_t size() const

    {

        return m_span.size() * 2 - 1;

    }

    T const& operator[](size_t index) const

    {

        // Follow the path:

        if (index < m_span.size())

            return m_span[index];

        // Then in reverse:

        if (index < size())

            return m_span[size() - index - 1];

        // Then wrap around again:

        return m_span[index - size() + 1];

    }

private:

    ReadonlySpan<T> m_span;

};

static Vector<FloatPoint, 128> make_pen(float thickness)

{

    constexpr auto flatness = 0.15f;

    auto pen_vertex_count = 4;

    if (thickness > flatness) {

        pen_vertex_count = max(

            static_cast<int>(ceilf(AK::Pi<float>

                / acosf(1 - (2 * flatness) / thickness))),

            pen_vertex_count);

    }

    if (pen_vertex_count % 2 == 1)

        pen_vertex_count += 1;

    Vector<FloatPoint, 128> pen_vertices;

    pen_vertices.ensure_capacity(pen_vertex_count);

    // Generate vertices for the pen (going counterclockwise). The pen does not necessarily need

    // to be a circle (or an approximation of one), but other shapes are untested.

    float theta = 0;

    float theta_delta = (AK::Pi<float> * 2) / pen_vertex_count;

    for (int i = 0; i < pen_vertex_count; i++) {

        float sin_theta;

        float cos_theta;

        AK::sincos(theta, sin_theta, cos_theta);

        pen_vertices.unchecked_append({ cos_theta * thickness / 2, sin_theta * thickness / 2 });

        theta -= theta_delta;

    }

    return pen_vertices;

}

static void apply_dash_pattern(Vector<Vector<FloatPoint>>& segments, Vector<bool>& segment_is_closed, Vector<float> dash_pattern, float dash_offset)

{

    VERIFY(!dash_pattern.is_empty());

    // Has to be ensured by callers. (They all double the list, but <canvas> needs to do that in a way that

    // is visible to JS accessors, so don't do it here.)

    VERIFY(dash_pattern.size() % 2 == 0);

    // This implementation is vaguely based on the <canvas> spec. One difference is that the <canvas> spec

    // modifies the path in place, while this implementation returns a new path. The spec is written in terms

    // of [start, end] intervals that are removed from the input path, while we have to instead add the

    // complement of those intervals to the output path. This is done by keeping track of the previous `end`

    // value and then filling in the gap between that and the current `start` value on every interval, and

    // at the end of each subpath.

    Vector<Vector<FloatPoint>> new_segments;

    // https://html.spec.whatwg.org/multipage/canvas.html#line-styles:dash-list-5

    // 7. Let `pattern width` be the concatenation of all the entries of style's dash list, in coordinate space units.

    // (NOTE: The spec means sum, not concatenation.)

    float pattern_width = 0;

    for (auto& entry : dash_pattern) {

        VERIFY(entry >= 0);

        pattern_width += entry;

    }

    // 8. For each subpath `subpath` in `path`, run the following substeps. These substeps mutate the subpaths in `path` in vivo.

    for (auto const& [subpath_index, subpath] : enumerate(segments)) {

        float end, last_end = 0;

        // 1. Let `subpath width` be the length of all the lines of `subpath`, in coordinate space units.

        float subpath_width = 0;

        for (size_t i = 0; i < subpath.size() - 1; i++)

            subpath_width += subpath[i].distance_from(subpath[i + 1]);

        // 2. Let `offset` be the value of style's lineDashOffset, in coordinate space units.

        float offset = dash_offset;

        // 3. While `offset` is greater than `pattern width`, decrement it by pattern width.

        //    While `offset` is less than zero, increment it by `pattern width`.

        // FIXME: Rewrite this using fmodf() in the future, once this has good test coverage.

        while (offset > pattern_width)

            offset -= pattern_width;

        while (offset < 0)

            offset += pattern_width;

        // 4. Define `L` to be a linear coordinate line defined along all lines in subpath, such that the start of the first line

        //    in the subpath is defined as coordinate 0, and the end of the last line in the subpath is defined as coordinate `subpath width`.

        float L = 0;

        size_t current_vertex_index = 0;

        auto next_L = [&]() -> float {

            return L + subpath[current_vertex_index].distance_from(subpath[current_vertex_index + 1]);

        };

        auto append_distinct = [](Vector<FloatPoint>& path, FloatPoint p) {

            if (path.is_empty() || path.last() != p)

                path.append(p);

        };

        auto skip_until = [&](float target_L) {

            while (next_L() < target_L) {

                L = next_L();

                current_vertex_index++;

            }

        };

        auto append_until = [&](Vector<FloatPoint>& new_subpath, float target_L) {

            while (next_L() < target_L) {

                L = next_L();

                current_vertex_index++;

                append_distinct(new_subpath, subpath[current_vertex_index]);

            }

        };

        auto append_lerp = [&](Vector<FloatPoint>& new_subpath, float target_L) {

            VERIFY(target_L >= L);

            VERIFY(target_L <= next_L());

            append_distinct(new_subpath, mix(subpath[current_vertex_index], subpath[current_vertex_index + 1], (target_L - L) / (next_L() - L)));

        };

        // 5. Let `position` be zero minus offset.

        float position = -offset;

        // 6. Let `index` be 0.

        size_t index = 0;

        // 7. Let `current state` be off (the other states being on and zero-on).

        // (NOTE: The mentioned "zero-on" state in the spec appears unused.)

        enum class State {

            Off,

            On,

        };

        State current_state = State::Off;

    dash_on:

        // 8. Dash on: Let `segment length` be the value of style's dash list's `index`th entry.

        float segment_length = dash_pattern[index];

        // 9. Increment `position` by `segment length`.

        position += segment_length;

        // 10. If `position` is greater than `subpath width`, then end these substeps for this subpath and start them again for the next subpath;

        //     if there are no more subpaths, then jump to the step labeled `convert` instead.

        if (position > subpath_width) {

            if (last_end < subpath_width) {

                // Fill from last_end to subpath_width.

                Vector<FloatPoint> new_subpath;

                skip_until(last_end);

                append_lerp(new_subpath, last_end);

                for (++current_vertex_index; current_vertex_index < subpath.size(); ++current_vertex_index)

                    append_distinct(new_subpath, subpath[current_vertex_index]);

                new_segments.append(move(new_subpath));

            }

            continue;

        }

        // 11. If `segment length` is nonzero, then let current state be on.

        if (segment_length != 0)

            current_state = State::On;

        // 12. Increment `index` by one.

        index++;

        // 13. Dash off: Let segment length be the value of style's dash list's `index`th entry.

        // (NOTE: The label "Dash off:" in the spec appears unused.)

        segment_length = dash_pattern[index];

        // 14. Let `start` be the offset `position` on L.

        float start = position;

        // 15. Increment `position` by `segment length`.

        position += segment_length;

        // 16. If `position` is less than zero, then jump to the step labeled `post-cut`.

        if (position < 0)

            goto post_cut;

        // 17. If `start` is less than zero, then let `start` be zero.

        if (start < 0)

            start = 0;

        // 18. If `position` is greater than `subpath width`, then let `end` be the offset `subpath width` on `L`. Otherwise, let `end` be the offset `position` on `L`.

        end = position > subpath_width ? subpath_width : position;

        // 19. Jump to the first appropriate step:

        //   If segment length is zero and current state is off

        //       Do nothing, just continue to the next step.

        //   If current state is off

        //       Cut the line on which `end` finds itself short at `end` and place a point there, cutting in two the subpath that it was in;

        //       remove all line segments, joins, points, and subpaths that are between `start` and `end`; and finally place a single point at

        //       `start` with no lines connecting to it.

        //       The point has a directionality for the purposes of drawing line caps (see below). The directionality is the direction that

        //       the original line had at that point (i.e. when `L` was defined above).

        //   Otherwise

        //       Cut the line on which `start` finds itself into two at `start` and place a point there, cutting in two the subpath that it was in,

        //       and similarly cut the line on which `end` finds itself short at end and place a point there, cutting in two the subpath that it was in,

        //       and then remove all line segments, joins, points, and subpaths that are between `start` and `end`.

        if (segment_length == 0 && current_state == State::Off) {

            // Do nothing.

        } else if (current_state == State::Off) {

            Vector<FloatPoint> new_subpath;

            skip_until(start);

            append_lerp(new_subpath, start);

            // FIXME: Store directionality.

            new_segments.append(move(new_subpath));

        } else {

            Vector<FloatPoint> new_subpath;

            skip_until(last_end);

            append_lerp(new_subpath, last_end);

            append_until(new_subpath, start);

            append_lerp(new_subpath, start);

            new_segments.append(move(new_subpath));

            last_end = end;

        }

        // 20. If start and end are the same point, then this results in just the line being cut in two and two points being inserted there,

        //     with nothing being removed, unless a join also happens to be at that point, in which case the join must be removed.

        // FIXME: Not clear if we have to do anything here, given our inverted interval implementation.

    post_cut:

        // 21. Post-cut: If position is greater than subpath width, then jump to the step labeled convert.

        if (position > subpath_width)

            break;

        // 22. If segment length is greater than zero, then let positioned-at-on-dash be false.

        // (NOTE: The spec doesn't mention positioned-at-on-dash anywhere else.)

        // 23. Increment index by one. If it is equal to the number of entries in style's dash list, then let index be 0.

        index++;

        if (index == dash_pattern.size())

            index = 0;

        // 24. Return to the step labeled `dash on`.

        goto dash_on;

    }

    segments = move(new_segments);

    // This function is only called if there are dashes, and dashes are never closed.

    segment_is_closed.resize(segments.size());

    for (auto& is_closed : segment_is_closed)

        is_closed = false;

}

Path Path::stroke_to_fill(StrokeStyle const& style) const

{

    // Note: This convolves a polygon with the path using the algorithm described

    // in https://keithp.com/~keithp/talks/cairo2003.pdf (3.1 Stroking Splines via Convolution)

    // Cap style handling is done by replacing the convolution with an explicit shape

    // at the path's ends, but we still maintain a position on the pen and pretend we're convolving.

    auto thickness = style.thickness;

    auto cap_style = style.cap_style;

    auto join_style = style.join_style;

    VERIFY(thickness > 0);

    auto lines = split_lines();

    if (lines.is_empty())

        return Path {};

    auto subpath_end_indices = split_lines_subbpath_end_indices();

    size_t current_subpath_end_indices_cursor = 0;

    // Paths can be disconnected, which a pain to deal with, so split it up.

    // Also filter out duplicate points here (but keep one-point paths around

    // since we draw round and square caps for them).

    Vector<Vector<FloatPoint>> segments;

    Vector<bool> segment_is_closed;

    segments.append({ lines.first().a() });

    for (auto const& [line_index, line] : enumerate(lines)) {

        bool previous_line_closed_segment = false;

        if (subpath_end_indices.size() > current_subpath_end_indices_cursor)

            previous_line_closed_segment = subpath_end_indices[current_subpath_end_indices_cursor] == line_index - 1;

        if (line.a() == segments.last().last() && !previous_line_closed_segment) {

            if (line.a() != line.b())

                segments.last().append(line.b());

        } else {

            segment_is_closed.append(previous_line_closed_segment);

            if (previous_line_closed_segment)

                current_subpath_end_indices_cursor++;

            segments.append({ line.a() });

            if (line.a() != line.b())

                segments.last().append(line.b());

        }

    }

    if (segment_is_closed.size() < segments.size()) {

        bool previous_line_closed_segment = false;

        if (subpath_end_indices.size() > current_subpath_end_indices_cursor)

            previous_line_closed_segment = subpath_end_indices[current_subpath_end_indices_cursor] == lines.size() - 1;

        segment_is_closed.append(previous_line_closed_segment);

        if (previous_line_closed_segment)

            current_subpath_end_indices_cursor++;

        VERIFY(segment_is_closed.size() == segments.size());

        VERIFY(current_subpath_end_indices_cursor == subpath_end_indices.size());

    }

    if (!style.dash_pattern.is_empty())

        apply_dash_pattern(segments, segment_is_closed, style.dash_pattern, style.dash_offset);

    Vector<FloatPoint, 128> pen_vertices = make_pen(thickness);

    static constexpr auto mod = [](int a, int b) {

        VERIFY(b > 0);

        VERIFY(a + b >= 0);

        return (a + b) % b;

    };

    auto wrapping_index = [](auto& vertices, auto index) {

        return vertices[mod(index, vertices.size())];

    };

Path.cpp:auto Gfx::Path::stroke_to_fill(Gfx::Path::StrokeStyle const&) const::$_0::operator()<AK::Vector<Gfx::Point<float>, 128ul>, int>(AK::Vector<Gfx::Point<float>, 128ul>&, int) const

Line

Count

Source

805

1.65M

    auto wrapping_index = [](auto& vertices, auto index) {

806

1.65M

        return vertices[mod(index, vertices.size())];

807

1.65M

    };

Unexecuted instantiation: Path.cpp:auto Gfx::Path::stroke_to_fill(Gfx::Path::StrokeStyle const&) const::$_0::operator()<AK::Vector<Gfx::Path::stroke_to_fill(Gfx::Path::StrokeStyle const&) const::ActiveRange, 128ul>, int>(AK::Vector<Gfx::Path::stroke_to_fill(Gfx::Path::StrokeStyle const&) const::ActiveRange, 128ul>&, int) const

    auto angle_between = [](auto p1, auto p2) {

        auto delta = p2 - p1;

        return atan2f(delta.y(), delta.x());

    };

    struct ActiveRange {

        float start;

        float end;

        bool in_range(float angle) const

        {

            // Note: Since active ranges go counterclockwise start > end unless we wrap around at 180 degrees

            return ((angle <= start && angle >= end)

                || (start < end && angle <= start)

                || (start < end && angle >= end));

        }

    };

    Vector<ActiveRange, 128> active_ranges;

    active_ranges.ensure_capacity(pen_vertices.size());

    for (int i = 0; i < (int)pen_vertices.size(); i++) {

        active_ranges.unchecked_append({ angle_between(wrapping_index(pen_vertices, i - 1), pen_vertices[i]),

            angle_between(pen_vertices[i], wrapping_index(pen_vertices, i + 1)) });

    }

    auto clockwise = [](float current_angle, float target_angle) {

        if (target_angle < 0)

            target_angle += AK::Pi<float> * 2;

        if (current_angle < 0)

            current_angle += AK::Pi<float> * 2;

        if (target_angle < current_angle)

            target_angle += AK::Pi<float> * 2;

        auto angle = target_angle - current_angle;

        // If the end of the range is antiparallel to where we want to go,

        // we have to keep moving clockwise: In that case, the _next_ range

        // is what we want.

        if (fabs(angle - AK::Pi<float>) < 0.0001f)

            return true;

        return angle <= AK::Pi<float>;

    };

    Path convolution;

    for (auto const& [segment_index, segment] : enumerate(segments)) {

        if (segment.size() < 2) {

            // Draw round and square caps for single-point segments.

            // FIXME: THis is is a bit ad-hoc. It matches what most PDF engines do,

            // and matches what Chrome and Firefox (but not WebKit) do for canvas paths.

            if (cap_style == CapStyle::Round) {

                convolution.move_to(segment[0] + pen_vertices[0]);

                for (int i = 1; i < (int)pen_vertices.size(); i++)

                    convolution.line_to(segment[0] + pen_vertices[i]);

                convolution.close();

            } else if (cap_style == CapStyle::Square) {

                convolution.rect({ segment[0].translated(-thickness / 2, -thickness / 2), { thickness, thickness } });

            }

            continue;

        }

        RoundTrip<FloatPoint> shape { segment };

        bool first = true;

        auto add_vertex = [&](auto v) {

            if (first) {

                convolution.move_to(v);

                first = false;

            } else {

                convolution.line_to(v);

            }

        };

        auto shape_idx = 0u;

        auto slope = [&] {

            return angle_between(shape[shape_idx], shape[shape_idx + 1]);

        };

        auto start_slope = slope();

        // Note: At least one range must be active.

        int active = *active_ranges.find_first_index_if([&](auto& range) {

            return range.in_range(start_slope);

        });

        shape_idx = 1;

        auto add_round_join = [&](unsigned next_index) {

            add_vertex(shape[shape_idx] + pen_vertices[active]);

            auto slope_now = angle_between(shape[shape_idx], shape[next_index]);

            auto range = active_ranges[active];

            while (!range.in_range(slope_now)) {

                active = mod(active + (clockwise(slope_now, range.end) ? 1 : -1), pen_vertices.size());

                add_vertex(shape[shape_idx] + pen_vertices[active]);

                range = active_ranges[active];

            }

        };

        auto add_bevel_join = [&](unsigned next_index) {

            add_vertex(shape[shape_idx] + pen_vertices[active]);

            auto slope_now = angle_between(shape[shape_idx], shape[next_index]);

            auto range = active_ranges[active];

            auto last_active = active;

            while (!range.in_range(slope_now)) {

                last_active = active;

                active = mod(active + (clockwise(slope_now, range.end) ? 1 : -1), pen_vertices.size());

                range = active_ranges[active];

            }

            if (last_active != active)

                add_vertex(shape[shape_idx] + pen_vertices[active]);

        };

        auto add_miter_join = [&](unsigned next_index) {

            auto cross_product = [](FloatPoint const& p1, FloatPoint const& p2) {

                return p1.x() * p2.y() - p1.y() * p2.x();

            };

            auto segment1 = shape[shape_idx] - shape[shape_idx - 1];

            auto normal1 = FloatVector2(-segment1.y(), segment1.x()).normalized();

            auto offset1 = FloatPoint(normal1.x(), normal1.y()) * (thickness / 2);

            auto p1 = shape[shape_idx - 1] + offset1;

            auto segment2 = shape[next_index] - shape[shape_idx];

            auto normal2 = FloatVector2(-segment2.y(), segment2.x()).normalized();

            auto offset2 = FloatPoint(normal2.x(), normal2.y()) * (thickness / 2);

            auto p2 = shape[shape_idx] + offset2;

            auto denominator = cross_product(segment1, segment2);

            if (denominator == 0)

                return add_bevel_join(next_index);

            auto intersection = p1 + segment1 * cross_product(p2 - p1, segment2) / denominator;

            if (intersection.distance_from(shape[shape_idx]) / (thickness / 2) > style.miter_limit)

                return add_bevel_join(next_index);

            add_vertex(intersection);

            auto slope_now = angle_between(shape[shape_idx], shape[next_index]);

            auto range = active_ranges[active];

            while (!range.in_range(slope_now)) {