C++ BreakIterator::following方法代码示例

// In the Unicode string characters are always stored in logical order.
// This makes line breaking easy. One word is added to the current line at a time. Once the line is too long
// we either go back one step or inset the line break at the current position (depending on "wrap_before" setting).
// At the end everything that is left over is added as the final line.
void text_layout::break_line(text_line & line, double wrap_width, unsigned text_ratio, bool wrap_before)
{
    shape_text(line);
    if (!wrap_width || line.width() < wrap_width)
    {
        add_line(line);
        return;

    }
    if (text_ratio)
    {
        double wrap_at;
        double string_width = line.width();
        double string_height = line.line_height();
        for (double i = 1.0; ((wrap_at = string_width/i)/(string_height*i)) > text_ratio && (string_width/i) > wrap_width; i += 1.0) ;
        wrap_width = wrap_at;
    }

    mapnik::value_unicode_string const& text = itemizer_.text();
    Locale locale; // TODO: Is the default constructor correct?
    UErrorCode status = U_ZERO_ERROR;
    BreakIterator *breakitr = BreakIterator::createLineInstance(locale, status);

    // Not breaking the text if an error occurs is probably the best thing we can do.
    // https://github.com/mapnik/mapnik/issues/2072
    if (!U_SUCCESS(status))
    {
        add_line(line);
        MAPNIK_LOG_ERROR(text_layout) << " could not create BreakIterator: " << u_errorName(status);
        return;
    }

    breakitr->setText(text);

    double current_line_length = 0;
    int last_break_position = static_cast<int>(line.first_char());
    for (unsigned i=line.first_char(); i < line.last_char(); ++i)
    {
        // TODO: character_spacing
        std::map<unsigned, double>::const_iterator width_itr = width_map_.find(i);
        if (width_itr != width_map_.end())
        {
            current_line_length += width_itr->second;
        }
        if (current_line_length <= wrap_width) continue;

        int break_position = wrap_before ? breakitr->preceding(i) : breakitr->following(i);
        // following() returns a break position after the last word. So DONE should only be returned
        // when calling preceding.
        if (break_position <= last_break_position || break_position == static_cast<int>(BreakIterator::DONE))
        {
            // A single word is longer than the maximum line width.
            // Violate line width requirement and choose next break position
            break_position = breakitr->following(i);
            if (break_position == static_cast<int>(BreakIterator::DONE))
            {
                break_position = line.last_char();
                MAPNIK_LOG_ERROR(text_layout) << "Unexpected result in break_line. Trying to recover...\n";
            }
        }
        // Break iterator operates on the whole string, while we only look at one line. So we need to
        // clamp break values.
        if (break_position < static_cast<int>(line.first_char()))
        {
            break_position = line.first_char();
        }
        if (break_position > static_cast<int>(line.last_char()))
        {
            break_position = line.last_char();
        }

        text_line new_line(last_break_position, break_position);
        clear_cluster_widths(last_break_position, break_position);
        shape_text(new_line);
        add_line(new_line);
        last_break_position = break_position;
        i = break_position - 1;
        current_line_length = 0;
    }
    if (last_break_position == static_cast<int>(line.first_char()))
    {
        // No line breaks => no reshaping required
        add_line(line);
    }
    else if (last_break_position != static_cast<int>(line.last_char()))
    {
        text_line new_line(last_break_position, line.last_char());
        clear_cluster_widths(last_break_position, line.last_char());
        shape_text(new_line);
        add_line(new_line);
    }
}

/* Print the element at a specified position */
void printAt(BreakIterator &boundary, int32_t pos )
{
    int32_t end = boundary.following(pos);
    int32_t start = boundary.previous();
    printTextRange( boundary, start, end );
}