Waveform: avoid QPaitner glitch with ranges < 1 px

src/waveform/renderers/waveformrendermarkrange.cpp

@@ -64,6 +64,13 @@ void WaveformRenderMarkRange::draw(QPainter *painter, QPaintEvent * /*event*/) {
 
         double startPosition = m_waveformRenderer->transformSamplePositionInRendererWorld(startSample);
         double endPosition = m_waveformRenderer->transformSamplePositionInRendererWorld(endSample);
+        double span = endPosition - startPosition;
+        // If span is < 1 painter would extend the rectangle to width() as long as
+        // startPosition is in view.
+        // TODO(xxx) Figure what's wrong with QPainter / the renderer
+        if (span < 1.0) {
+            span = 1.0;
+        }
 
         //range not in the current display
         if (startPosition > m_waveformRenderer->getLength() || endPosition < 0) {
@@ -78,9 +85,9 @@ void WaveformRenderMarkRange::draw(QPainter *painter, QPaintEvent * /*event*/) {
         // this shouldn't involve *any* scaling it should be fast even in software mode
         QRectF rect;
         if (m_waveformRenderer->getOrientation() == Qt::Horizontal) {
-            rect.setRect(startPosition, 0, endPosition - startPosition, m_waveformRenderer->getHeight());
+            rect.setRect(startPosition, 0, span, m_waveformRenderer->getHeight());
         } else {
-            rect.setRect(0, startPosition, m_waveformRenderer->getWidth(), endPosition - startPosition);
+            rect.setRect(0, startPosition, m_waveformRenderer->getWidth(), span);
         }
         painter->drawImage(rect, *selectedImage, rect);
     }