Waveform: fix shifted pixmap markers with odd scale factors

src/waveform/renderers/waveformrendermark.cpp

@@ -149,14 +149,20 @@ void WaveformRenderMark::generateMarkImage(WaveformMarkPointer pMark) {
     float devicePixelRatio = m_waveformRenderer->getDevicePixelRatio();
     if (!pMark->m_pixmapPath.isEmpty()) {
         QString path = pMark->m_pixmapPath;
-        QImage image = *WImageStore::getImage(path, scaleFactor());
+        // Dse devicePixelRatio to properly scale the image
+        QImage image = *WImageStore::getImage(path, devicePixelRatio);
         //QImage image = QImage(path);
         // If loading the image didn't fail, then we're done. Otherwise fall
         // through and render a label.
         if (!image.isNull()) {
             pMark->m_image =
                     image.convertToFormat(QImage::Format_ARGB32_Premultiplied);
             //WImageStore::correctImageColors(&pMark->m_image);
+            // Do this in order to get a truely scaled image, not just a blurry one.
+            // See https://doc.qt.io/qt-5/qimage.html#setDevicePixelRatio
+            // Without this some Qt internal issue results in an offset image
+            // when calculating the center line in draw()
+            pMark->m_image.setDevicePixelRatio(devicePixelRatio);
             return;
         }
     }