--- /dev/null
+#include <QPainter>
+
+#include "correlation_meter.h"
+
+using namespace std;
+
+CorrelationMeter::CorrelationMeter(QWidget *parent)
+ : QWidget(parent)
+{
+}
+
+void CorrelationMeter::resizeEvent(QResizeEvent *event)
+{
+ on_pixmap = QPixmap(width(), height());
+ QPainter on_painter(&on_pixmap);
+ QLinearGradient on(0, 0, width(), 0);
+ on.setColorAt(0.0f, QColor(255, 0, 0));
+ on.setColorAt(0.5f, QColor(255, 255, 0));
+ on.setColorAt(0.8f, QColor(0, 255, 0));
+ on.setColorAt(0.95f, QColor(255, 255, 0));
+ on_painter.fillRect(0, 0, width(), height(), Qt::black);
+ on_painter.fillRect(1, 1, width() - 2, height() - 2, on);
+
+ off_pixmap = QPixmap(width(), height());
+ QPainter off_painter(&off_pixmap);
+ QLinearGradient off(0, 0, width(), 0);
+ off.setColorAt(0.0f, QColor(127, 0, 0));
+ off.setColorAt(0.5f, QColor(127, 127, 0));
+ off.setColorAt(0.8f, QColor(0, 127, 0));
+ off.setColorAt(0.95f, QColor(127, 127, 0));
+ off_painter.fillRect(0, 0, width(), height(), Qt::black);
+ off_painter.fillRect(1, 1, width() - 2, height() - 2, off);
+}
+
+void CorrelationMeter::paintEvent(QPaintEvent *event)
+{
+ QPainter painter(this);
+
+ float correlation;
+ {
+ unique_lock<mutex> lock(correlation_mutex);
+ correlation = this->correlation;
+ }
+
+ // Just in case.
+ correlation = std::min(std::max(correlation, -1.0f), 1.0f);
+
+ int pos = 3 + lrintf(0.5f * (correlation + 1.0f) * (width() - 6));
+ QRect off_rect(0, 0, width(), height());
+ QRect on_rect(pos - 2, 0, 5, height());
+
+ painter.drawPixmap(off_rect, off_pixmap, off_rect);
+ painter.drawPixmap(on_rect, on_pixmap, on_rect);
+}