Method fill_border_jump

source/matplot/axes_objects/contours.cpp:625–734

Generate points to close a polygon if not closed yet Some polygons might not be closed yet. Large polygons that end on borders might not be going around the borders properly as it should. That's fine for lines but it's not fine for filled curves. In these cases, we have to sanitize and continue clockwise or anticlockwise around the borders until we reach the initial point. If they start or end o

    /// go around the borders. In these cases, the contourc
    /// algorithm does not close the polygons for us.
    std::pair<vector_1d, vector_1d>
    contours::fill_border_jump(double start_x, double start_y, double end_x,
                               double end_y, double x_min, double x_max,
                               double y_min, double y_max, bool is_parent) {
        // start_b = identify if starting border W,S,E,N
        constexpr uint8_t NONE = 0;
        constexpr uint8_t NORTH = 1;
        constexpr uint8_t SOUTH = 2;
        constexpr uint8_t WEST = 3;
        constexpr uint8_t EAST = 4;
        uint8_t xy1_border = NONE;
        if (start_x <= x_min) {
            xy1_border = WEST;
        } else if (start_x >= x_max) {
            xy1_border = EAST;
        } else if (start_y <= y_min) {
            xy1_border = SOUTH;
        } else if (start_y >= y_max) {
            xy1_border = NORTH;
        }
        if (xy1_border == NONE) {
            return {};
        }

        // end_b   = identify if closing border border W,S,E,N
        uint8_t xy2_border = NONE;
        if (end_x <= x_min) {
            xy2_border = WEST;
        } else if (end_x >= x_max) {
            xy2_border = EAST;
        } else if (end_y <= y_min) {
            xy2_border = SOUTH;
        } else if (end_y >= y_max) {
            xy2_border = NORTH;
        }
        if (xy2_border == NONE) {
            return {};
        }

        // parents go anticlockwise
        // we need to know the direction we should use to fill the border
        const bool clockwise = !is_parent;

        std::pair<vector_1d, vector_1d> result;
        if (clockwise) {
            while (xy1_border != xy2_border) {
                switch (xy1_border) {
                case WEST:
                    // append NW
                    result.first.emplace_back(x_min);
                    result.second.emplace_back(y_max);
                    xy1_border = NORTH;
                    break;
                case NORTH:
                    // append NE
                    result.first.emplace_back(x_max);
                    result.second.emplace_back(y_max);
                    xy1_border = EAST;