qt5base-lts/tests/manual/textrendering/textperformance/main.cpp

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** Copyright (C) 2020 The Qt Company Ltd.
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** This file is part of the test suite of the Qt Toolkit.
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** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
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#include <QApplication>
#include <QDialog>
#include <QFontDatabase>
#include <QPainter>
#include <QRandomGenerator>
#include <QElapsedTimer>
#include <QTimer>

static const int lastMeasurementsCount = 50;

class FontBlaster: public QWidget
{
    Q_OBJECT

public:
    FontBlaster(QWidget *parent = 0)
        : QWidget(parent)
        , m_currentMode(0)
    {
        setFocusPolicy(Qt::StrongFocus);
    }

    void paintEvent(QPaintEvent *event)
    {
        Q_UNUSED(event);
        QPainter p(this);

        if (m_timer.isValid())
            m_lastMeasurements.append(m_timer.elapsed());
        m_timer.start();

        p.save();
        m_modes[m_currentMode].function(p, size());
        p.restore();

        const QFontMetrics fm = p.fontMetrics();
        p.setOpacity(0.7);
        p.fillRect(0, 0, width(), fm.height(), Qt::gray);
        p.fillRect(0, height() - fm.height(), width(), height(), Qt::gray);
        p.setOpacity(1);
        p.setPen(palette().color(QPalette::Text));
        p.drawText(2, fm.ascent(), m_modes[m_currentMode].name);

        if (m_lastMeasurements.count() == lastMeasurementsCount) {
            m_lastMeasurements.removeFirst();
            int lastMsecsSum = 0;
            foreach(const int measurement, m_lastMeasurements)
                lastMsecsSum += measurement;

            p.drawText(2, height() - fm.descent(),
                QLatin1String("Fps: ") +
                QString::number(1000 / ((qreal)lastMsecsSum / lastMeasurementsCount), 'f', 1)
            );
        }

        QTimer::singleShot(0, this, SLOT(repaint()));
    }

    /*
      Creating all kinds of size/weight/italic combinations, stress testing
      the glyph cache.
      Also: painting with different opacities, stress testing blitting.
    */
    static void paintDifferentFontStyles(QPainter &p, const QSize &size)
    {
        static const QString text = QLatin1String("Qt rocks!!!");
        static const int textsPerPaint = 30;
        for (int i = 0; i < textsPerPaint; i++) {
            const int fontSize = 4 + QRandomGenerator::global()->bounded(5);
            const int fontWeight = QRandomGenerator::global()->bounded(2) == 1 ? QFont::Normal : QFont::Bold;
            const bool fontItalic = QRandomGenerator::global()->bounded(2) == 1;
            const QFont font("Default", fontSize, fontWeight, fontItalic);
            p.setFont(font);
            p.setPen(QColor::fromHsv(QRandomGenerator::global()->bounded(359), 155 + QRandomGenerator::global()->bounded(100),
                                     155 + QRandomGenerator::global()->bounded(100), 100 + QRandomGenerator::global()->bounded(155)));
            const QSize textSize(p.fontMetrics().boundingRect(text).size());
            const QPoint position(
                -textSize.width() / 2 + QRandomGenerator::global()->bounded(size.width()),
                textSize.height() / 2 + QRandomGenerator::global()->bounded(size.height()));
            p.drawText(position, text);
        }
    }

    /*
      Drawing a multiline latin text, stress testing the text layout system.
    */
    static void paintLongLatinText(QPainter &p, const QSize &size)
    {
        static const char* const pieces[] = {
            "lorem ipsum",
            "dolor sit amet",
            "consectetuer",
            "sed diam nonumy",
            "eos et accusam",
            "sea takimata sanctus"
        };
        static const int piecesCount = (int)(sizeof pieces / sizeof pieces[0]);
        static const int piecesPerPaint = 30;

        QString text;
        for (int i = 0; i < piecesPerPaint; ++i) {
            QString piece = QLatin1String(pieces[QRandomGenerator::global()->bounded(piecesCount)]);
            if (i == 0 || QRandomGenerator::global()->bounded(2)) {
                // Make this piece the beginning of a new sentence.
                piece[0] = piece[0].toUpper();
                if (i > 0)
                    piece.prepend(QLatin1String(". "));
            } else {
                piece.prepend(QLatin1String(", "));
            }
            text.append(piece);
        }
        text.append(QLatin1Char('.'));

        p.drawText(QRectF(QPointF(0, 0), QSizeF(size)),
                   Qt::AlignTop | Qt::AlignAbsolute | Qt::TextWordWrap, text);
    }

    /*
      Drawing one text with several snippets of different writingSystems, stress
      testing the font merging in the font database.
    */
    static void paintInternationalText(QPainter &p, const QSize &size)
    {
        static QStringList samples;
        if (samples.isEmpty()) {
            foreach (const QFontDatabase::WritingSystem system, QFontDatabase::writingSystems())
                if (system != QFontDatabase::Ogham && system != QFontDatabase::Runic)
                    samples.append(QFontDatabase::writingSystemSample(system));
        }
        static const int systemsPerPaint = 65;
        QString text;
        for (int i = 0; i < systemsPerPaint; i++) {
            if (i > 0)
                text.append(QLatin1Char(' '));
            text.append(samples.at(QRandomGenerator::global()->bounded(samples.count())));
        }
        p.drawText(QRectF(QPointF(0, 0), QSizeF(size)),
                   Qt::AlignTop | Qt::AlignAbsolute | Qt::TextWordWrap, text);
    }

protected:
    void nextMode()
    {
        m_currentMode = (m_currentMode + 1) % m_modesCount;
        m_lastMeasurements.clear();
    }

    void keyPressEvent(QKeyEvent *event)
    {
        Q_UNUSED(event);
        nextMode();
    }

    void mousePressEvent(QMouseEvent *event)
    {
        Q_UNUSED(event);
        nextMode();
    }

private:
    static const struct mode {
        QString name;
        void (*function)(QPainter &, const QSize&);
    } m_modes[];
    static const int m_modesCount;

    int m_currentMode;
    QList<int> m_lastMeasurements;
    QElapsedTimer m_timer;
};

const struct FontBlaster::mode FontBlaster::m_modes[] = {
    { QLatin1String("Qt rocks!!!"), FontBlaster::paintDifferentFontStyles },
    { QLatin1String("Latin"), FontBlaster::paintLongLatinText },
    { QLatin1String("International"), FontBlaster::paintInternationalText }
};

const int FontBlaster::m_modesCount =
    (int)(sizeof m_modes / sizeof m_modes[0]);

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    FontBlaster dlg;
    dlg.show();

    return a.exec();
}

#include "main.moc"