viewer: began waveformview widget

app/widget/viewer/waveformview.cpp

@@ -0,0 +1,24 @@
+#include "waveformview.h"
+
+#include <QPainter>
+#include <QtMath>
+
+WaveformView::WaveformView(QWidget *parent) :
+  TimeBasedWidget(parent)
+{
+  setAutoFillBackground(true);
+  setStyleSheet("background: black;");
+}
+
+void WaveformView::paintEvent(QPaintEvent *event)
+{
+  QWidget::paintEvent(event);
+
+  QPainter p(this);
+
+  p.setPen(Qt::green);
+
+  for (int i=0;i<width();i++) {
+    p.drawPoint(i, (height() / 2) + qSin(static_cast<double>(i) * 0.025) * (height() / 2));
+  }
+}