blame: src/imageviewwidget.cpp

#include "imageviewwidget.h"

#include <QPainter>

#include <QKeyEvent>

#include <QMouseEvent>

#include <QImageReader>

#include <algorithm>

ImageViewWidget::ImageViewWidget(QWidget *parent)

    : QWidget(parent)

{

    setFocusPolicy(Qt::StrongFocus);

    setStyleSheet("background-color: black;");

}

void ImageViewWidget::setImage(const QString &path)

{

    QImageReader reader(path);

    reader.setAutoTransform(true);

    QImage image = reader.read();

    if (!image.isNull())

        m_pixmap = QPixmap::fromImage(image);

    else

        m_pixmap = QPixmap();

    m_zoomMode = FitToScreen;

    m_zoomFactor = 1.0;

    m_offset = QPoint(0, 0);

    update();

}

void ImageViewWidget::paintEvent(QPaintEvent *)

{

    if (m_pixmap.isNull())

        return;

    QPainter painter(this);

    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);

}

void ImageViewWidget::keyPressEvent(QKeyEvent *event)

{

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

    {

        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;

    }

    QWidget::keyPressEvent(event);

}

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::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);

    }

}