Improve responsiveness of drag seek during click-scrub...

.. by refreshing the TrackPanel window less often.

src/SelectedRegion.h

@@ -256,6 +256,19 @@ private:
    }
 #endif
 
+   friend inline bool operator ==
+   (const SelectedRegion &lhs, const SelectedRegion &rhs)
+   {
+      return
+            lhs.mT0 == rhs.mT0
+         && lhs.mT1 == rhs.mT1
+#ifdef EXPERIMENTAL_SPECTRAL_EDITING
+         && lhs.mF0 == rhs.mF0
+         && lhs.mF1 == rhs.mF1
+#endif
+      ;
+   }
+
    double mT0;
    double mT1;
 #ifdef EXPERIMENTAL_SPECTRAL_EDITING
@@ -265,4 +278,9 @@ private:
 
 };
 
+inline bool operator != (const SelectedRegion &lhs, const SelectedRegion &rhs)
+{
+   return !(lhs == rhs);
+}
+
 #endif

src/TrackPanel.cpp

@@ -944,6 +944,9 @@ void TrackPanel::OnTimer(wxTimerEvent& )
       //ANSWER-ME: Was DisplaySelection added to solve a repaint problem?
       DisplaySelection();
    }
+   if (mLastDrawnSelectedRegion != mViewInfo->selectedRegion) {
+      UpdateSelectionDisplay();
+   }
 
    // Notify listeners for timer ticks
    {
@@ -1045,6 +1048,8 @@ double TrackPanel::GetScreenEndTime() const
 ///  completing a repaint operation.
 void TrackPanel::OnPaint(wxPaintEvent & /* event */)
 {
+   mLastDrawnSelectedRegion = mViewInfo->selectedRegion;
+
 #if DEBUG_DRAW_TIMING
    wxStopWatch sw;
 #endif
@@ -2764,7 +2769,9 @@ void TrackPanel::SelectionHandleDrag(wxMouseEvent & event, Track *clickedTrack)
 #endif
 
    ExtendSelection(x, rect.x, clickedTrack);
-   UpdateSelectionDisplay();
+   // Don't do this at every mouse event, because it slows down seek-scrub.
+   // Instead, let OnTimer do it, which is often enough.
+   // UpdateSelectionDisplay();
 }
 
 #ifdef EXPERIMENTAL_SPECTRAL_EDITING

src/TrackPanel.h

@@ -790,6 +790,8 @@ protected:
    // The screenshot class needs to access internals
    friend class ScreenshotCommand;
 
+   SelectedRegion mLastDrawnSelectedRegion {};
+
  public:
    wxSize vrulerSize;