Implemented basic preview!

audioplayer.cpp

@@ -59,8 +59,11 @@ void AudioPlayer::writeSamples(frame_t *begin, frame_t *end)
 
     m_position = position;
     const auto now = QDateTime::currentDateTime();
-    if (m_lastPositionUpdate.isNull() || m_lastPositionUpdate.msecsTo(now) > 100)
+    if (m_lastPositionUpdate.isNull() || m_lastPositionUpdate.msecsTo(now) > 1000/30)
+    {
         emit positionChanged(m_position);
+        m_lastPositionUpdate = now;
+    }
 
     if (ended)
         emit playingChanged(m_playing = false);

graphrenderer.cpp

@@ -15,17 +15,16 @@ QPixmap GraphRenderer::render(const QSize &size, const frame_t *frameBegin, cons
 
     painter.fillRect(pixmap.rect(), palette.base());
 
-    painter.setPen(Qt::white);
-    painter.setBrush(Qt::black);
+    painter.setBrush(palette.base());
 
-    painter.drawRect(QRect({}, size));
+    painter.drawRect(pixmap.rect());
 
-    render(size, frameBegin, frameEnd, painter, palette);
+    render(pixmap.rect(), frameBegin, frameEnd, painter, palette);
     painter.end();
     return pixmap;
 }
 
-void GraphRenderer::render(const QSize &size, const frame_t *frameBegin, const frame_t *frameEnd, QPainter &painter, const QPalette &palette)
+void GraphRenderer::render(const QRect &rect, const frame_t *frameBegin, const frame_t *frameEnd, QPainter &painter, const QPalette &palette)
 {
     if (frameEnd == frameBegin)
         return;
@@ -33,9 +32,9 @@ void GraphRenderer::render(const QSize &size, const frame_t *frameBegin, const f
     painter.setPen(QPen{palette.color(QPalette::Text)});
     painter.setBrush(palette.text());
 
-    const auto framesPerPixel = std::distance(frameBegin, frameEnd) / size.width();
+    const auto framesPerPixel = std::distance(frameBegin, frameEnd) / rect.width();
 
-    for (int x = 0; x < size.width(); x++)
+    for (int x = 0; x < rect.width(); x++)
     {
         const frame_t *begin = frameBegin + (x * framesPerPixel);
         const frame_t *end = begin + framesPerPixel;
@@ -53,7 +52,7 @@ void GraphRenderer::render(const QSize &size, const frame_t *frameBegin, const f
                 max[1] = (*iter)[1];
         }
 
-        painter.drawLine(x, (size.height() / 2) - (min[0] * (size.height() / 2)),
-                         x, (size.height() / 2) + (max[0] * (size.height() / 2)));
+        painter.drawLine(rect.x() + x, rect.y() + (rect.height() / 2) - (min[0] * (rect.height() / 2)),
+                         rect.x() + x, rect.y() + (rect.height() / 2) + (max[0] * (rect.height() / 2)));
     }
 }

graphrenderer.h

@@ -10,5 +10,5 @@ class QPalette;
 namespace GraphRenderer
 {
     QPixmap render(const QSize &size, const frame_t *frameBegin, const frame_t *frameEnd, const QPalette &palette);
-    void render(const QSize &size, const frame_t *frameBegin, const frame_t *frameEnd, QPainter &painter, const QPalette &palette);
+    void render(const QRect &rect, const frame_t *frameBegin, const frame_t *frameEnd, QPainter &painter, const QPalette &palette);
 }

previewwidget.cpp

@@ -27,7 +27,7 @@ void PreviewWidget::paintEvent(QPaintEvent *event)
         painter.drawRect(m_graphCache.rect());
 
         if (m_buffer.isValid())
-            GraphRenderer::render(size(), m_buffer.constData<frame_t>(), m_buffer.constData<frame_t>() + m_buffer.frameCount(), painter, palette());
+            GraphRenderer::render(m_graphCache.rect(), m_buffer.constData<frame_t>(), m_buffer.constData<frame_t>() + m_buffer.frameCount(), painter, palette());
 
         painter.end();
     }

scratchwidget.cpp

@@ -1,9 +1,13 @@
 #include "scratchwidget.h"
 
 #include <QPainter>
+#include <QRect>
+#include <QDebug>
 
 #include "graphrenderer.h"
 
+constexpr auto theWidth = 100;
+
 ScratchWidget::ScratchWidget(QWidget *parent) :
     QWidget{parent}
 {
@@ -18,6 +22,29 @@ void ScratchWidget::paintEvent(QPaintEvent *event)
     painter.setBrush(palette().window());
     painter.drawRect(rect());
 
+    if (m_buffer.isValid() && m_position < m_buffer.frameCount() - sampleRate)
+    {
+        {
+            QPen pen{Qt::blue};
+            pen.setWidth(3);
+            painter.setPen(pen);
+        }
+
+        const auto doit = [&](int offset)
+        {
+            int x = ((width()/2)-(float(m_position % sampleRate) / sampleRate * theWidth)) + (theWidth*offset);
+            const auto pixmap = getPixmap((m_position/sampleRate)+offset);
+            if (!pixmap.isNull())
+                painter.drawPixmap(x, 0, pixmap);
+        };
+
+        doit(-2);
+        doit(-1);
+        doit(0);
+        doit(1);
+        doit(2);
+    }
+
     {
         QPen pen{Qt::red};
         pen.setWidth(3);
@@ -43,3 +70,25 @@ void ScratchWidget::mouseMoveEvent(QMouseEvent *event)
 {
 
 }
+
+QPixmap ScratchWidget::getPixmap(int index)
+{
+    {
+        const auto pixmap = m_graphCache[index];
+        if (pixmap)
+            return *pixmap;
+    }
+
+    if (!m_buffer.isValid() || index < 0 || index >= m_buffer.frameCount()/sampleRate)
+    {
+        qWarning() << index;
+        return {};
+    }
+
+    const auto *begin = m_buffer.constData<frame_t>() + (index*sampleRate);
+    const auto pixmap = GraphRenderer::render(QSize{theWidth, height()}, begin, begin+sampleRate, palette());
+
+    m_graphCache.insert(index, new QPixmap{pixmap});
+
+    return pixmap;
+}

scratchwidget.h

@@ -1,9 +1,8 @@
 #pragma once
 
-#include <vector>
-
 #include <QWidget>
 #include <QAudioBuffer>
+#include <QCache>
 
 class ScratchWidget : public QWidget
 {
@@ -15,8 +14,8 @@ public:
     const QAudioBuffer &buffer() const { return m_buffer; }
     void setBuffer(const QAudioBuffer &buffer) { m_buffer = buffer; m_graphCache.clear(); repaint(); }
 
-    double position() const { return m_position; }
-    void setPosition(double position) { m_position = position; repaint(); }
+    std::size_t position() const { return m_position; }
+    void setPosition(std::size_t position) { m_position = position; repaint(); }
 
 protected:
     void paintEvent(QPaintEvent *event) override;
@@ -25,7 +24,9 @@ protected:
     void mouseMoveEvent(QMouseEvent *event) override;
 
 private:
+    QPixmap getPixmap(int index);
+
     QAudioBuffer m_buffer;
-    double m_position{};
-    std::vector<QPixmap> m_graphCache;
+    std::size_t m_position{};
+    QCache<int, QPixmap> m_graphCache;
 };