annotation.cpp

用qt做的城市电子地图

#include <QtGui>
#include <cmath>

#include "annotation.h"

Annotation::Annotation(const QString &text, bool major)
{
    font = qApp->font();
    font.setBold(true);
    if (major) {
        font.setPointSize(font.pointSize() + 2);
        font.setStretch(QFont::SemiExpanded);
    }

    if (major) {
        threshold = 0.01 * (40 + (std::rand() % 40));
    } else {
        threshold = 0.01 * (100 + (std::rand() % 100));
    }

    str = text;
    this->major = major;
    y = 20 - (std::rand() % 40);

    setZValue(1000);
    setFlag(ItemIgnoresTransformations, true);
}

void Annotation::setText(const QString &text)
{
    prepareGeometryChange();
    str = text;
    update();
}

QString Annotation::text() const
{
    return str;
}

QRectF Annotation::boundingRect() const
{
    QFontMetricsF metrics(font);
    QRectF rect = metrics.boundingRect(str);
    rect.moveCenter(QPointF(0, y));
    rect.adjust(-4, 0, +4, 0);
    return rect;
}

void Annotation::paint(QPainter *painter,
                       const QStyleOptionGraphicsItem *option,
                       QWidget * /* widget */)
{
    if (option->levelOfDetail <= threshold)
        return;

    painter->setFont(font);

    QRectF rect = boundingRect();

    int alpha = int(30 * std::log(option->levelOfDetail));
    if (alpha >= 32)
        painter->fillRect(rect, QColor(255, 255, 255, qMin(alpha, 63)));

    painter->setPen(Qt::white);
    painter->drawText(rect.translated(+1, +1), str,
                      QTextOption(Qt::AlignCenter));
    painter->setPen(Qt::blue);
    painter->drawText(rect, str, QTextOption(Qt::AlignCenter));
}