Method OnPaint

src/TrackPanel.cpp:485–532

AS: OnPaint( ) is called during the normal course of completing a repaint operation.

/// AS: OnPaint( ) is called during the normal course of
///  completing a repaint operation.
void TrackPanel::OnPaint(wxPaintEvent & /* event */)
{
   // If the selected region changes - we must repaint the tracks, because the
   // selection is baked into track image
   if (mLastDrawnSelectedRegion != mViewInfo->selectedRegion)
   {
      mRefreshBacking = true;
      mLastDrawnSelectedRegion = mViewInfo->selectedRegion;
   }

   auto sw =
      FrameStatistics::CreateStopwatch(FrameStatistics::SectionID::TrackPanel);

   {
      wxPaintDC dc(this);

      // Retrieve the damage rectangle
      wxRect box = GetUpdateRegion().GetBox();

      // Recreate the backing bitmap if we have a full refresh
      // (See TrackPanel::Refresh())
      if (mRefreshBacking || (box == GetRect()))
      {
         // Reset (should a mutex be used???)
         mRefreshBacking = false;

         // Redraw the backing bitmap
         DrawTracks(&GetBackingDCForRepaint());

         // Copy it to the display
         DisplayBitmap(dc);
      }
      else
      {
         // Copy full, possibly clipped, damage rectangle
         RepairBitmap(dc, box.x, box.y, box.width, box.height);
      }

      // Done with the clipped DC

      // Drawing now goes directly to the client area.
      // DrawOverlays() may need to draw outside the clipped region.
      // (Used to make a NEW, separate wxClientDC, but that risks flashing
      // problems on Mac.)
      dc.DestroyClippingRegion();
      DrawOverlays(true, &dc);
   }
}

void TrackPanel::MakeParentRedrawScrollbars()
{