audacity/src/widgets/OverlayPanel.cpp

//
//  OverlayPanel.cpp
//  Audacity
//
//  Created by Paul Licameli on 5/7/16.
//
//

#include "../Audacity.h"
#include "OverlayPanel.h"

#include "Overlay.h"
#include <algorithm>
#include <wx/dcclient.h>

OverlayPanel::OverlayPanel(wxWindow * parent, wxWindowID id,
             const wxPoint & pos,
             const wxSize & size,
             long style)
: BackedPanel(parent, id, pos, size, style)
{}

void OverlayPanel::AddOverlay( const std::weak_ptr<Overlay> &pOverlay)
{
   if (pOverlay.expired())
      return;
   Compress();
   auto iter = std::lower_bound( mOverlays.begin(), mOverlays.end(),
      pOverlay.lock()->SequenceNumber(),
      []( const OverlayPtr &p, unsigned value ) {
         return p.expired() || p.lock()->SequenceNumber() < value;
      }
   );
   mOverlays.insert(iter, pOverlay);
}

void OverlayPanel::ClearOverlays()
{
   mOverlays.clear();
}

void OverlayPanel::DrawOverlays(bool repaint_all, wxDC *pDC)
{
   size_t n_pairs = mOverlays.size();

   using Pair = std::pair<wxRect, bool /*out of date?*/>;
   std::vector< Pair > pairs;
   pairs.reserve(n_pairs);

   // First...
   Compress();
   // ... then assume pointers are not expired

   // Find out the rectangles and outdatedness for each overlay
   wxSize size(GetBackingDC().GetSize());
   for (const auto pOverlay : mOverlays)
      pairs.push_back( pOverlay.lock()->GetRectangle(size) );

   // See what requires redrawing.  If repainting, all.
   // If not, then whatever is outdated, and whatever will be damaged by
   // undrawing.
   // By redrawing only what needs it, we avoid flashing things like
   // the cursor that are drawn with invert, and also avoid
   // unnecessary work.

   // But first, a quick exit test.
   bool some_overlays_need_repainting =
      repaint_all ||
      std::any_of( pairs.begin(), pairs.end(),
         []( const Pair &pair ){ return pair.second; } );

   if (!some_overlays_need_repainting) {
     // This function (OverlayPanel::DrawOverlays()) is called at
     // fairly high frequency through a timer in TrackPanel. In case
     // there is nothing to do, we exit early because creating the
     // wxClientDC below is expensive, at least on Linux.
     return;
   }

   if (!repaint_all) {
      // For each overlay that needs update, any other overlay whose
      // rectangle instersects it will also need update.
      bool done;
      do {
         done = true;
         for (size_t ii = 0; ii < n_pairs - 1; ++ii) {
            for (size_t jj = ii + 1; jj < n_pairs; ++jj) {
               if (pairs[ii].second != pairs[jj].second &&
                   pairs[ii].first.Intersects(pairs[jj].first)) {
                  done = false;
                  pairs[ii].second = pairs[jj].second = true;
               }
            }
         }
      } while (!done);
   }

   Maybe<wxClientDC> myDC;
   auto &dc = pDC ? *pDC : (myDC.create(this), *myDC);

   // Erase
   auto it2 = pairs.begin();
   for (auto pOverlay : mOverlays) {
      if (repaint_all || it2->second)
         pOverlay.lock()->Erase(dc, GetBackingDC());
      ++it2;
   }

   // Draw
   it2 = pairs.begin();
   for (auto pOverlay : mOverlays) {
      if (repaint_all || it2->second) {
         // Guarantee a clean state of the dc each pass:
         ADCChanger changer{ &dc };

         pOverlay.lock()->Draw(*this, dc);
      }
      ++it2;
   }
}

void OverlayPanel::Compress()
{
   // remove any expired pointers
   auto begin = mOverlays.begin();
   auto end = mOverlays.end();
   auto newEnd = std::remove_if( begin, end,
      []( const std::weak_ptr<Overlay> &pOverlay ){
         return pOverlay.expired(); } );
   if ( end != newEnd )
      mOverlays.resize( newEnd - begin );
}

BEGIN_EVENT_TABLE(OverlayPanel, BackedPanel)
END_EVENT_TABLE()

// Maybe this class needs a better home
void DCUnchanger::operator () (wxDC *pDC) const
{
   if (pDC) {
      pDC->SetPen(pen);
      pDC->SetBrush(brush);
      pDC->SetLogicalFunction(wxRasterOperationMode(logicalOperation));
   }
}

ADCChanger::ADCChanger(wxDC *pDC)
   : Base{ pDC, ::DCUnchanger{ pDC->GetBrush(), pDC->GetPen(),
      long(pDC->GetLogicalFunction()) } }
{}