Implemeted scratching

scratchwidget.cpp

@@ -2,6 +2,7 @@
 
 #include <QPainter>
 #include <QRect>
+#include <QMouseEvent>
 #include <QDebug>
 
 #include "graphrenderer.h"
@@ -11,6 +12,9 @@ constexpr auto theWidth = 100;
 ScratchWidget::ScratchWidget(QWidget *parent) :
     QWidget{parent}
 {
+    connect(&m_timer, &QTimer::timeout, this, &ScratchWidget::timeout);
+    m_timer.setSingleShot(true);
+    m_timer.setInterval(100);
 }
 
 void ScratchWidget::paintEvent(QPaintEvent *event)
@@ -58,17 +62,46 @@ void ScratchWidget::paintEvent(QPaintEvent *event)
 
 void ScratchWidget::mousePressEvent(QMouseEvent *event)
 {
-
+    if (event->button() == Qt::LeftButton)
+    {
+        m_scratching = true;
+        m_mouseX = event->x();
+        m_timestamp = QDateTime::currentDateTime();
+        setMouseTracking(true);
+    }
 }
 
 void ScratchWidget::mouseReleaseEvent(QMouseEvent *event)
 {
-
+    if (event->button() == Qt::LeftButton)
+    {
+        m_timer.stop();
+        emit scratchSpeed(1.f);
+        m_scratching = false;
+        setMouseTracking(false);
+    }
 }
 
 void ScratchWidget::mouseMoveEvent(QMouseEvent *event)
 {
+    if (m_scratching)
+    {
+        const auto now = QDateTime::currentDateTime();
 
+        int dx = m_mouseX - event->x();
+        int dt = m_timestamp.msecsTo(now);
+
+        emit scratchSpeed(float(dx) / dt * 5.f);
+
+        m_mouseX = event->x();
+        m_timestamp = now;
+        m_timer.start();
+    }
+}
+
+void ScratchWidget::timeout()
+{
+    emit scratchSpeed(0.f);
 }
 
 QPixmap ScratchWidget::getPixmap(int index)

scratchwidget.h

@@ -3,6 +3,8 @@
 #include <QWidget>
 #include <QAudioBuffer>
 #include <QCache>
+#include <QDateTime>
+#include <QTimer>
 
 class ScratchWidget : public QWidget
 {
@@ -17,16 +19,27 @@ public:
     std::size_t position() const { return m_position; }
     void setPosition(std::size_t position) { m_position = position; repaint(); }
 
+signals:
+    void scratchSpeed(float speed);
+
 protected:
     void paintEvent(QPaintEvent *event) override;
     void mousePressEvent(QMouseEvent *event) override;
     void mouseReleaseEvent(QMouseEvent *event) override;
     void mouseMoveEvent(QMouseEvent *event) override;
 
+private slots:
+    void timeout();
+
 private:
     QPixmap getPixmap(int index);
 
     QAudioBuffer m_buffer;
     std::size_t m_position{};
     QCache<int, QPixmap> m_graphCache;
+
+    bool m_scratching{};
+    int m_mouseX;
+    QDateTime m_timestamp;
+    QTimer m_timer;
 };

trackdeck.cpp

@@ -29,6 +29,7 @@ TrackDeck::TrackDeck(QWidget *parent) :
 
     connect(m_ui->previewWidget, &PreviewWidget::positionSelected, &m_player, &AudioPlayer::setPosition);
     connect(&m_player, &AudioPlayer::positionChanged, m_ui->previewWidget, &PreviewWidget::setPosition);
+    connect(m_ui->scratchWidget, &ScratchWidget::scratchSpeed, &m_player, &AudioPlayer::setSpeed);
     connect(&m_player, &AudioPlayer::positionChanged, m_ui->scratchWidget, &ScratchWidget::setPosition);
     connect(&m_player, &AudioPlayer::playingChanged, m_ui->pushButtonPlay, [&button=*m_ui->pushButtonPlay](bool playing){ button.setText(playing ? tr("▮▮") : tr("▶")); });
 }