SpectrumAnalyzer/stretchtitlelabel.cpp at main · mohammadHaghpanah/SpectrumAnalyzer · GitHub

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/**
 * @file stretchtitlelabel.cpp
 * @brief Implements leading-letter stretch animation for the app title.
 */

#include "stretchtitlelabel.h"

#include <QAbstractAnimation>
#include <QColor>
#include <QEasingCurve>
#include <QFontMetrics>
#include <QPainter>
#include <QPaintEvent>
#include <QTimer>
#include <QVariantAnimation>

StretchTitleLabel::StretchTitleLabel(QWidget *parent)
    : QLabel(parent)
{
    m_anim = new QVariantAnimation(this);
    m_anim->setDuration(900);
    m_anim->setStartValue(1.0);
    m_anim->setKeyValueAt(0.45, 1.85);
    m_anim->setEndValue(1.0);
    m_anim->setEasingCurve(QEasingCurve::InOutCubic);
    connect(m_anim, &QVariantAnimation::valueChanged, this, [this](const QVariant &v) {
        setStretch(v.toReal());
    });

    m_idleTimer = new QTimer(this);
    m_idleTimer->setInterval(3500);
    connect(m_idleTimer, &QTimer::timeout, this, &StretchTitleLabel::startStretchPulse);
    m_idleTimer->start();

    // First pulse shortly after the window appears.
    QTimer::singleShot(900, this, &StretchTitleLabel::startStretchPulse);
}

void StretchTitleLabel::setPulseEnabled(bool enabled)
{
    if (enabled) {
        if (!m_idleTimer->isActive()) {
            m_idleTimer->start();
        }
        return;
    }
    m_idleTimer->stop();
    m_anim->stop();
    setStretch(1.0);
}

qreal StretchTitleLabel::stretch() const
{
    return m_stretch;
}

void StretchTitleLabel::setStretch(qreal value)
{
    m_stretch = qMax(1.0, value);
    update();
}

void StretchTitleLabel::startStretchPulse()
{
    if (m_anim->state() == QAbstractAnimation::Running) {
        return;
    }
    m_anim->stop();
    m_anim->setCurrentTime(0);
    m_anim->start();
}

void StretchTitleLabel::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);

    const QString full = text();
    if (full.isEmpty()) {
        return;
    }

    QPainter p(this);
    p.setRenderHint(QPainter::TextAntialiasing, true);
    p.setRenderHint(QPainter::Antialiasing, true);
    p.setFont(font());
    p.setPen(palette().color(QPalette::WindowText));

    // Prefer stylesheet/color from QLabel when available.
    const QColor ink = QColor(QStringLiteral("#111111"));
    p.setPen(ink);

    const QFontMetrics fm(font());
    const QString first = full.left(1);
    const QString rest = full.mid(1);

    const int firstW = fm.horizontalAdvance(first);
    const int restW = fm.horizontalAdvance(rest);
    const int stretchedFirstW = qRound(firstW * m_stretch);
    const int totalW = stretchedFirstW + restW;
    const int baseY = (height() + fm.ascent() - fm.descent()) / 2;
    const int startX = 0; // left-aligned like the original title block

    auto drawAt = [&](int y, const QColor &color) {
        p.setPen(color);
        p.save();
        p.translate(startX, y);
        p.scale(m_stretch, 1.0);
        p.drawText(0, baseY, first);
        p.restore();
        p.drawText(startX + stretchedFirstW, baseY + y, rest);
    };

    drawAt(2, QColor(0, 0, 0, 90));
    drawAt(0, QColor(QStringLiteral("#111111")));

    Q_UNUSED(totalW);
}