blame: src/imageviewwidget.cpp

#include "imageviewwidget.h"

#include <QPainter>

#include <QKeyEvent>

#include <QMouseEvent>

#include <QFile>

#include <QImageReader>

#include <QPalette>

#include <algorithm>

#include <iostream>

#include <fcntl.h>

#include <unistd.h>

// --- ImageLoadWorker ---

ImageLoadWorker::ImageLoadWorker(const QByteArray &path, QObject *parent)

    : QThread(parent), m_path(path)

{

}

// THREADING: This function runs on its own QThread, NOT the main thread.

// It must not access any ImageViewWidget member state.  The only data it uses

// is m_path which is immutable after construction.  The emitted imageLoaded()

// signal is delivered to the main thread via Qt::AutoConnection which resolves

// to QueuedConnection at emit time (worker thread != receiver's main-thread

// affinity), so onImageLoaded() always executes on the main thread.

void ImageLoadWorker::run()

{

    int fd = ::open(m_path.constData(), O_RDONLY | O_CLOEXEC);

    if (fd < 0) {

        emit imageLoaded(m_path, QPixmap{});

        return;

    }

    QFile file;

    if (!file.open(fd, QIODevice::ReadOnly, QFileDevice::AutoCloseHandle)) {

        ::close(fd);

        emit imageLoaded(m_path, QPixmap{});

        return;

    }

    QImageReader reader(&file);

    reader.setAutoTransform(true);

    reader.setDecideFormatFromContent(true);

    reader.setAllocationLimit(0);

    QImage image = reader.read();

    QPixmap pixmap;

    if (!image.isNull()) {

        if (image.format() != QImage::Format_RGB32

            && image.format() != QImage::Format_ARGB32

            && image.format() != QImage::Format_ARGB32_Premultiplied)

            image = image.convertToFormat(QImage::Format_ARGB32);

        pixmap = QPixmap::fromImage(image);

    }

    emit imageLoaded(m_path, pixmap);

}

// --- ImageViewWidget ---

ImageViewWidget::ImageViewWidget(QWidget *parent)

    : QWidget(parent)

{

    setFocusPolicy(Qt::StrongFocus);

    setAutoFillBackground(true);

    setBackgroundColor("black");

}

QPixmap ImageViewWidget::loadImageFromDisk(const QByteArray &path)

{

    int fd = ::open(path.constData(), O_RDONLY | O_CLOEXEC);

    if (fd < 0)

        return {};

    QFile file;

    if (!file.open(fd, QIODevice::ReadOnly, QFileDevice::AutoCloseHandle)) {

        ::close(fd);

        return {};

    }

    QImageReader reader(&file);

    reader.setAutoTransform(true);

    reader.setDecideFormatFromContent(true);

    reader.setAllocationLimit(0);

    QImage image = reader.read();

    if (!image.isNull()) {

        if (image.format() != QImage::Format_RGB32

            && image.format() != QImage::Format_ARGB32

            && image.format() != QImage::Format_ARGB32_Premultiplied)

            image = image.convertToFormat(QImage::Format_ARGB32);

        return QPixmap::fromImage(image);

    }

    return {};

}

void ImageViewWidget::setImage(const QByteArray &path)

{

    m_currentPath = path;

    m_exifData = ExifData{}; // clear stale EXIF until new data is set

    // Check cache first

    if (m_cache.contains(path)) {

        m_pixmap = m_cache[path];

    } else {

        m_pixmap = loadImageFromDisk(path);

        m_cache[path] = m_pixmap;

    }

    m_zoomMode = FitToScreen;

    m_zoomFactor = 1.0;

    m_offset = QPoint(0, 0);

    update();

    // Trigger prefetch of neighbors if they have been set

    if (!m_neighborPaths.isEmpty()) {

        // Evict entries that are no longer in the neighbor window

        QSet<QByteArray> keep(m_neighborPaths.begin(), m_neighborPaths.end());

        keep.insert(m_currentPath);

        for (auto it = m_cache.begin(); it != m_cache.end(); ) {

            if (!keep.contains(it.key()))

                it = m_cache.erase(it);

            else

                ++it;

        }

        // Prefetch neighbors that are not yet cached

        for (const QByteArray &neighbor : m_neighborPaths) {

            prefetchImage(neighbor);

        }

    }

}

void ImageViewWidget::prefetchImage(const QByteArray &path)

{

    if (m_cache.contains(path) || m_pendingLoads.contains(path))

        return;

    m_pendingLoads.insert(path);

    auto *worker = new ImageLoadWorker(path, this);

    // THREADING: Qt::AutoConnection (default) resolves to QueuedConnection at

    // emit time because ImageLoadWorker::run() emits from its worker thread

    // while 'this' (ImageViewWidget) has main-thread affinity.  This guarantees

    // onImageLoaded() always runs on the main thread — no mutex needed.

    connect(worker, &ImageLoadWorker::imageLoaded, this, &ImageViewWidget::onImageLoaded);

    connect(worker, &QThread::finished, worker, &QObject::deleteLater);

    worker->start();

}

void ImageViewWidget::onImageLoaded(const QByteArray &path, const QPixmap &pixmap)

{

    m_pendingLoads.remove(path);

    // Only cache if path is still relevant (current or a neighbor)

    QSet<QByteArray> keep(m_neighborPaths.begin(), m_neighborPaths.end());

    keep.insert(m_currentPath);

    if (keep.contains(path)) {

        m_cache[path] = pixmap;

    }

}

void ImageViewWidget::setNeighborPaths(const QList<QByteArray> &paths)

{

    m_neighborPaths = paths;

}

void ImageViewWidget::clearCache()

{

    m_cache.clear();

    m_neighborPaths.clear();

}

void ImageViewWidget::setBackgroundColor(const QString &color)

{

    m_backgroundColor = color;

    QPalette pal = palette();

    pal.setColor(QPalette::Window, QColor(color));

    setPalette(pal);

    update();

}

void ImageViewWidget::paintEvent(QPaintEvent *)

{

    if (m_pixmap.isNull())

        return;

    QPainter painter(this);

    painter.setRenderHint(QPainter::SmoothPixmapTransform, true);

    painter.setRenderHint(QPainter::Antialiasing, true);

    QPixmap drawn;

    switch (m_zoomMode) {

    case FitToScreen:

        drawn = m_pixmap.scaled(size(), Qt::KeepAspectRatio, Qt::SmoothTransformation);

        break;

    case OriginalSize:

        drawn = m_pixmap;

        break;

    case CustomZoom: {

        QSize target(static_cast<int>(m_pixmap.width() * m_zoomFactor),

                     static_cast<int>(m_pixmap.height() * m_zoomFactor));

        drawn = m_pixmap.scaled(target, Qt::KeepAspectRatio, Qt::SmoothTransformation);

        break;

    }

    }

    clampOffset(drawn.width(), drawn.height());

    int x = (width()  - drawn.width())  / 2 + m_offset.x();

    int y = (height() - drawn.height()) / 2 + m_offset.y();

    painter.drawPixmap(x, y, drawn);

    // EXIF overlay — top-right corner, toggled with 'i'

    if (m_showExifOverlay) {

        const auto fields = m_exifData.toList();

        if (!fields.isEmpty()) {

            const int padding = 10;

            const int lineH = 18;

            QFont font = painter.font();

            font.setPointSize(9);

            painter.setFont(font);

            QFontMetrics fm(font);

            int maxW = 0;

            for (const auto &f : fields)

                maxW = qMax(maxW, fm.horizontalAdvance(f.first + QLatin1String(": ") + f.second));

            const int boxW = maxW + padding * 2;

            const int boxH = fields.size() * lineH + padding * 2;

            const int boxX = width() - boxW - padding;

            const int boxY = padding;

            painter.save();

            painter.setPen(Qt::NoPen);

            painter.setBrush(QColor(0, 0, 0, 160));

            painter.drawRoundedRect(boxX, boxY, boxW, boxH, 8, 8);

            painter.setPen(Qt::white);

            for (int i = 0; i < fields.size(); ++i) {

                const QString line = fields[i].first + QLatin1String(": ") + fields[i].second;

                painter.drawText(boxX + padding,

                                 boxY + padding + fm.ascent() + i * lineH,

                                 line);

            }

            painter.restore();

        }

    }

    // Caption-Abstract overlay — bottom-centre, always shown when non-empty

    if (!m_exifData.captionAbstract.isEmpty()) {

        const int padding  = 10;

        const int margin   = 20;  // distance from bottom edge

        const int maxWidth = width() * 3 / 4;

        QFont captionFont = painter.font();

        captionFont.setPointSize(11);

        painter.setFont(captionFont);

        QFontMetrics cfm(captionFont);

        QRect textBounds = cfm.boundingRect(

            QRect(0, 0, maxWidth, 0),

            Qt::AlignHCenter | Qt::TextWordWrap,

            m_exifData.captionAbstract);

        const int boxW = textBounds.width()  + padding * 2;

        const int boxH = textBounds.height() + padding * 2;

        const int boxX = (width() - boxW) / 2;

        const int boxY = height() - boxH - margin;

        painter.save();

        painter.setPen(Qt::NoPen);

        painter.setBrush(QColor(0, 0, 0, 180));

        painter.drawRoundedRect(boxX, boxY, boxW, boxH, 8, 8);

        painter.setPen(Qt::white);

        painter.drawText(QRect(boxX + padding, boxY + padding, textBounds.width(), textBounds.height()),

                         Qt::AlignHCenter | Qt::TextWordWrap,

                         m_exifData.captionAbstract);

        painter.restore();

    }

    // Help overlay — centered, toggled with F1

    if (m_showHelpOverlay) {

        static const QPair<QString, QString> shortcuts[] = {

            {QStringLiteral("F1"),           QStringLiteral("Show/hide keyboard shortcuts")},

            {QStringLiteral("Esc / Enter"),  QStringLiteral("Close viewer")},

            {QStringLiteral("PgDn / PgUp"),  QStringLiteral("Next / previous image")},

            {QStringLiteral("\u2190 \u2192 \u2191 \u2193"),

                                             QStringLiteral("Pan image")},

            {QStringLiteral("/"),            QStringLiteral("Zoom to original size")},

            {QStringLiteral("*"),            QStringLiteral("Zoom to fit screen")},

            {QStringLiteral("+ / \u2212"),   QStringLiteral("Zoom in / out")},

            {QStringLiteral("I"),            QStringLiteral("Toggle EXIF info")},

            {QStringLiteral("E"),            QStringLiteral("Edit caption")},

            {QStringLiteral("F11"),          QStringLiteral("Toggle fullscreen")},

        };

        const int count = static_cast<int>(std::size(shortcuts));

        const int padding = 16;

        const int lineH   = 22;

        const int colGap  = 20;

        QFont font = painter.font();

        font.setPointSize(10);

        painter.setFont(font);

        QFontMetrics fm(font);

        int keyColW  = 0;

        int descColW = 0;

        for (const auto &s : shortcuts) {

            keyColW  = qMax(keyColW,  fm.horizontalAdvance(s.first));

            descColW = qMax(descColW, fm.horizontalAdvance(s.second));

        }

        const int boxW = padding + keyColW + colGap + descColW + padding;

        const int boxH = count * lineH + padding * 2;

        const int boxX = (width()  - boxW) / 2;

        const int boxY = (height() - boxH) / 2;

        painter.save();

        painter.setPen(Qt::NoPen);

        painter.setBrush(QColor(0, 0, 0, 200));

        painter.drawRoundedRect(boxX, boxY, boxW, boxH, 10, 10);

        for (int i = 0; i < count; ++i) {

            const int textY = boxY + padding + fm.ascent() + i * lineH;

            // Key column — right-aligned, light lavender

            painter.setPen(QColor(180, 180, 255));

            painter.drawText(QRect(boxX + padding, textY - fm.ascent(), keyColW, lineH),

                             Qt::AlignRight | Qt::AlignVCenter,

                             shortcuts[i].first);

            // Description column — left-aligned, white

            painter.setPen(Qt::white);

            painter.drawText(QRect(boxX + padding + keyColW + colGap,

                                   textY - fm.ascent(), descColW, lineH),

                             Qt::AlignLeft | Qt::AlignVCenter,

                             shortcuts[i].second);

        }

        painter.restore();

    }

}

void ImageViewWidget::keyPressEvent(QKeyEvent *event)

{

    if (event->key() == Qt::Key_F1)

    {

        m_showHelpOverlay = !m_showHelpOverlay;

        update();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_Escape || event->key() == Qt::Key_Return || event->key() == Qt::Key_Enter)

    {

        emit closeRequested();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_PageDown)

    {

        emit nextRequested();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_PageUp)

    {

        emit previousRequested();

        event->accept();

        return;

    }

    // Arrow keys for panning

    constexpr int panStep = 50;

    if (event->key() == Qt::Key_Left)

    {

        m_offset.rx() += panStep;

        update();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_Right)

    {

        m_offset.rx() -= panStep;

        update();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_Up)

    {

        m_offset.ry() += panStep;

        update();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_Down)

    {

        m_offset.ry() -= panStep;

        update();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_Slash)

    {

        zoomOriginal();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_Asterisk)

    {

        zoomFitToScreen();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_Plus)

    {

        zoomIn();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_Minus)

    {

        zoomOut();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_I)

    {

        toggleExifOverlay();

        event->accept();

        return;

    }

    if (event->key() == Qt::Key_E)

    {

        emit editCaptionRequested();

        event->accept();

        return;

    }

    QWidget::keyPressEvent(event);

}

void ImageViewWidget::setExifData(const ExifData &data)

{

    m_exifData = data;

    if (m_showExifOverlay)

        update();

}

void ImageViewWidget::toggleExifOverlay()

{

    m_showExifOverlay = !m_showExifOverlay;

    update();

}

QByteArray ImageViewWidget::currentPath() const

{

    return m_currentPath;

}

void ImageViewWidget::zoomIn()

{

    if (m_zoomMode == FitToScreen) {

        // Calculate the current effective scale so zooming feels continuous

        double sx = static_cast<double>(width()) / m_pixmap.width();

        double sy = static_cast<double>(height()) / m_pixmap.height();

        m_zoomFactor = std::min(sx, sy);

    }

    m_zoomFactor *= 1.25;

    m_zoomMode = CustomZoom;

    update();

}

void ImageViewWidget::zoomOut()

{

    if (m_zoomMode == FitToScreen) {

        double sx = static_cast<double>(width()) / m_pixmap.width();

        double sy = static_cast<double>(height()) / m_pixmap.height();

        m_zoomFactor = std::min(sx, sy);

    }

    m_zoomFactor /= 1.25;

    if (m_zoomFactor < 0.01)

        m_zoomFactor = 0.01;

    m_zoomMode = CustomZoom;

    update();

}

void ImageViewWidget::zoomOriginal()

{

    m_zoomMode = OriginalSize;

    m_zoomFactor = 1.0;

    update();

}

void ImageViewWidget::zoomFitToScreen()

{

    m_zoomMode = FitToScreen;

    m_offset = QPoint(0, 0);

    update();

}

void ImageViewWidget::mousePressEvent(QMouseEvent *event)

{

    if (event->button() == Qt::LeftButton) {

        m_dragging = true;

        m_dragStart = event->pos();

        m_offsetAtDragStart = m_offset;

        setCursor(Qt::ClosedHandCursor);

        event->accept();

    }

}

void ImageViewWidget::mouseMoveEvent(QMouseEvent *event)

{

    if (m_dragging) {

        m_offset = m_offsetAtDragStart + (event->pos() - m_dragStart);

        update();

        event->accept();

    }

}

void ImageViewWidget::mouseReleaseEvent(QMouseEvent *event)

{

    if (event->button() == Qt::LeftButton && m_dragging) {

        m_dragging = false;

        setCursor(Qt::ArrowCursor);

        event->accept();

    }

}

void ImageViewWidget::mouseDoubleClickEvent(QMouseEvent *event)

{

    if (event->button() == Qt::LeftButton) {

        emit closeRequested();

        event->accept();

    }

}

void ImageViewWidget::clampOffset(int imgW, int imgH)

{

    // Only allow panning when the drawn image exceeds the widget

    int overflowX = imgW - width();

    int overflowY = imgH - height();

    if (overflowX <= 0)

        m_offset.rx() = 0;

    else {

        int limit = overflowX / 2;

        m_offset.rx() = std::clamp(m_offset.x(), -limit, limit);

    }

    if (overflowY <= 0)

        m_offset.ry() = 0;

    else {

        int limit = overflowY / 2;

        m_offset.ry() = std::clamp(m_offset.y(), -limit, limit);

    }

}