First try

osciwidget.cpp

@@ -0,0 +1,108 @@
+#include "osciwidget.h"
+
+#include <cmath>
+
+#include <QLine>
+
+namespace {
+constexpr auto framerate = 60;
+constexpr auto blend = 190;
+}
+
+template<typename T>
+auto pythagoras(const T &dx, const T &dy)
+{
+    return std::sqrt(dx * dx + dy * dy);
+}
+
+auto pythagoras(const QLine &line)
+{
+    return pythagoras(line.dx(), line.dy());
+}
+
+OsciWidget::OsciWidget(QWidget *parent) :
+    QWidget(parent), m_timerId(startTimer(1000/framerate))
+{
+    resizePixmap();
+    m_timer.start();
+}
+
+void OsciWidget::samplesReceived(const SamplePair *begin, const SamplePair *end)
+{
+    QPainter painter;
+    painter.begin(&m_pixmap);
+    painter.setCompositionMode(QPainter::CompositionMode_Plus);
+
+    QPen pen;
+    pen.setWidth(2);
+
+    for (auto i = begin; i < end; i++)
+    {
+        const qint32 x = (float(i->x) / std::numeric_limits<qint16>::max() / 2 * width() * 2) + (width() / 2);
+        const qint32 y = (float(-i->y) / std::numeric_limits<qint16>::max() / 2 * height() * 2) + (height() / 2);
+        const QPoint p{x,y};
+
+        if (Q_LIKELY(m_lastPoint.has_value()))
+        {
+            auto dist = pythagoras(QLine(*m_lastPoint, p));
+            if (dist < 1)
+                dist = 1;
+
+            pen.setColor(QColor(0, 1./dist*255, 0));
+            painter.setPen(pen);
+
+            painter.drawLine(*m_lastPoint, p);
+        }
+
+        m_lastPoint = p;
+    }
+
+    painter.end();
+
+    if (m_timer.hasExpired(1000/framerate))
+    {
+        repaint();
+        m_timer.restart();
+    }
+}
+
+void OsciWidget::paintEvent(QPaintEvent *event)
+{
+    Q_UNUSED(event)
+
+    QPainter painter;
+    painter.begin(this);
+    painter.drawPixmap(0, 0, m_pixmap);
+    painter.end();
+
+    painter.begin(&m_pixmap);
+    painter.setCompositionMode(QPainter::CompositionMode_Multiply);
+    painter.drawPixmap(0, 0, m_fadeoutPixmap);
+    painter.end();
+}
+
+void OsciWidget::timerEvent(QTimerEvent *event)
+{
+    if (event->timerId() == m_timerId)
+    {
+        //repaint();
+    }
+    else
+        QWidget::timerEvent(event);
+}
+
+void OsciWidget::resizeEvent(QResizeEvent *event)
+{
+    Q_UNUSED(event)
+
+    resizePixmap();
+}
+
+void OsciWidget::resizePixmap()
+{
+    m_pixmap = QPixmap(size());
+    m_pixmap.fill(QColor());
+
+    m_fadeoutPixmap = QPixmap(size());
+    m_fadeoutPixmap.fill(QColor(blend, blend, blend));
+}