Reimplement quick play indicator as an overlay like the cursor

src/TrackPanel.cpp

@@ -550,8 +550,6 @@ TrackPanel::TrackPanel(wxWindow * parent, wxWindowID id,
    mSnapLeft = -1;
    mSnapRight = -1;
 
-   mOldQPIndicatorPos = -1;
-
    // Register for tracklist updates
    mTracks->Connect(EVT_TRACKLIST_RESIZED,
                     wxCommandEventHandler(TrackPanel::OnTrackListResized),
@@ -1039,47 +1037,6 @@ void TrackPanel::ScrollDuringDrag()
    }
 }
 
-void TrackPanel::DrawQuickPlayIndicator(int x, bool snapped)
-{
-   wxClientDC dc(this);
-
-   // Erase the old indicator.
-   if (mOldQPIndicatorPos != x) {
-#if defined(__WXMAC__)
-      // On OSX, if a HiDPI resolution is being used, the line will actually take up
-      // more than 1 pixel (even though it is drawn as 1), so we restore the surrounding
-      // pixels as well.  (This is because the wxClientDC doesn't know about the scaling.)
-      dc.Blit(mOldQPIndicatorPos - 1, 0, 3, mBacking->GetHeight(), &mBackingDC, mOldQPIndicatorPos - 1, 0);
-#else
-      dc.Blit(mOldQPIndicatorPos, 0, 1, mBacking->GetHeight(), &mBackingDC, mOldQPIndicatorPos, 0);
-#endif
-
-      mOldQPIndicatorPos = -1;
-   }
-
-   if (x >= 0) {
-      snapped ? AColor::SnapGuidePen(&dc) : AColor::Light(&dc, false);
-
-      // Draw indicator in all visible tracks
-      VisibleTrackIterator iter(GetProject());
-      for (Track *t = iter.First(); t; t = iter.Next())
-      {
-         // Convert virtual coordinate to physical
-         int y = t->GetY() - mViewInfo->vpos;
-
-         // Draw the NEW indicator in its new location
-         AColor::Line(dc,
-                      x,
-                      y + kTopMargin,
-                      x,
-                      // Minus one more because AColor::Line includes both endpoints
-                      y + t->GetHeight() - kBottomMargin - 1 );
-      }
-
-      mOldQPIndicatorPos = x;
-   }
-}
-
 double TrackPanel::GetScreenEndTime() const
 {
    int width;

src/TrackPanel.h

@@ -229,8 +229,6 @@ class AUDACITY_DLL_API TrackPanel final : public wxPanel {
    virtual void UpdateTrackVRuler(Track *t);
    virtual void UpdateVRulerSize();
 
-   virtual void DrawQuickPlayIndicator(int x, bool snapped = false);
-
    // Returns the time corresponding to the pixel column one past the track area
    // (ignoring any fisheye)
    virtual double GetScreenEndTime() const;
@@ -566,9 +564,6 @@ protected:
      TrackPanel *parent;
    } mTimer;
 
-   // Quick-Play indicator postion
-   int mOldQPIndicatorPos;
-
    int mTimeCount;
 
    wxMemoryDC mBackingDC;

src/widgets/Ruler.cpp

@@ -66,6 +66,7 @@ array of Ruler::Label.
 #include <wx/menuitem.h>
 #include <wx/tooltip.h>
 
+#include "../AColor.h"
 #include "../AudioIO.h"
 #include "../Internat.h"
 #include "../Project.h"
@@ -75,6 +76,8 @@ array of Ruler::Label.
 #include "../Experimental.h"
 #include "../TimeTrack.h"
 #include "../TrackPanel.h"
+#include "../TrackPanelCellIterator.h"
+#include "../TrackPanelOverlay.h"
 #include "../Menus.h"
 #include "../NumberScale.h"
 #include "../Prefs.h"
@@ -1643,6 +1646,91 @@ void RulerPanel::DoSetSize(int x, int y,
    ruler.SetBounds(0, 0, w-1, h-1);
 }
 
+/**********************************************************************
+
+QuickPlayIndicatorOverlay.
+Graphical helper for AdornedRulerPanel.
+
+**********************************************************************/
+
+class QuickPlayIndicatorOverlay final : public TrackPanelOverlay
+{
+public:
+   QuickPlayIndicatorOverlay(AudacityProject *project)
+      : mProject(project)
+      , mOldQPIndicatorPos(-1)
+      , mNewQPIndicatorPos(-1)
+      , mOldQPIndicatorSnapped(false)
+      , mNewQPIndicatorSnapped(false)
+   {
+   }
+
+   virtual ~QuickPlayIndicatorOverlay()
+   {
+   }
+
+   void Update(int x, bool snapped = false)
+   {
+      mNewQPIndicatorPos = x;
+      mNewQPIndicatorSnapped = snapped;
+
+      // Not strictly needed, but this reduces the lag in updating
+      // track panel causing momentary mismatch between the triangle
+      // in the ruler and the white line.
+
+      mProject->GetTrackPanel()->DrawOverlays(false);
+   }
+
+private:
+   std::pair<wxRect, bool> DoGetRectangle(wxSize size) override;
+   void Draw
+      (wxDC &dc, TrackPanelCellIterator begin, TrackPanelCellIterator end) override;
+
+   AudacityProject *mProject;
+   int mOldQPIndicatorPos;
+   int mNewQPIndicatorPos;
+   bool mOldQPIndicatorSnapped;
+   bool mNewQPIndicatorSnapped;
+};
+
+std::pair<wxRect, bool> QuickPlayIndicatorOverlay::DoGetRectangle(wxSize size)
+{
+   wxRect rect(mOldQPIndicatorPos, 0, 1, size.GetHeight());
+   return std::make_pair(
+      rect,
+      (mOldQPIndicatorPos != mNewQPIndicatorPos ||
+      mOldQPIndicatorSnapped != mNewQPIndicatorSnapped)
+   );
+}
+
+void QuickPlayIndicatorOverlay::Draw
+(wxDC &dc, TrackPanelCellIterator begin, TrackPanelCellIterator end)
+{
+   mOldQPIndicatorPos = mNewQPIndicatorPos;
+   mOldQPIndicatorSnapped = mNewQPIndicatorSnapped;
+
+   if (mOldQPIndicatorPos >= 0) {
+      mOldQPIndicatorSnapped ? AColor::SnapGuidePen(&dc) : AColor::Light(&dc, false);
+
+      // Draw indicator in all visible tracks
+      for (; begin != end; ++begin)
+      {
+         TrackPanelCellIterator::value_type data(*begin);
+         Track *const pTrack = dynamic_cast<Track*>(data.first);
+         if (!pTrack)
+            continue;
+         const wxRect &rect = data.second;
+
+         // Draw the NEW indicator in its NEW location
+         AColor::Line(dc,
+            mOldQPIndicatorPos,
+            rect.GetTop(),
+            mOldQPIndicatorPos,
+            rect.GetBottom());
+      }
+   }
+}
+
 /**********************************************************************
 
   Implementation of AdornedRulerPanel.
@@ -2525,6 +2613,16 @@ void AdornedRulerPanel::DoDrawIndicator(wxDC * dc)
    dc->DrawPolygon( 3, tri );
 }
 
+QuickPlayIndicatorOverlay *AdornedRulerPanel::GetOverlay()
+{
+   if (!mOverlay) {
+      TrackPanel *tp = mProject->GetTrackPanel();
+      mOverlay = std::make_unique<QuickPlayIndicatorOverlay>(mProject);
+      tp->AddOverlay(mOverlay.get());
+   }
+   return mOverlay.get();
+}
+
 // Draws the vertical line and green triangle indicating the Quick Play cursor position.
 void AdornedRulerPanel::DrawQuickPlayIndicator(wxDC * dc)
 {
@@ -2532,7 +2630,7 @@ void AdornedRulerPanel::DrawQuickPlayIndicator(wxDC * dc)
 
    double latestEnd = std::max(mTracks->GetEndTime(), mProject->GetSel1());
    if (dc == NULL || (mQuickPlayPos >= latestEnd)) {
-      tp->DrawQuickPlayIndicator(-1);
+      GetOverlay()->Update(-1);
       mLastQuickPlayX = -1;
       return;
    }
@@ -2564,7 +2662,7 @@ void AdornedRulerPanel::DrawQuickPlayIndicator(wxDC * dc)
    AColor::IndicatorColor( dc, true);
    dc->DrawPolygon( 3, tri, x );
 
-   tp->DrawQuickPlayIndicator(x, mIsSnapped);
+   GetOverlay()->Update(x, mIsSnapped);
 }
 
 void AdornedRulerPanel::SetPlayRegion(double playRegionStart,

src/widgets/Ruler.h

@@ -11,6 +11,7 @@
 #ifndef __AUDACITY_RULER__
 #define __AUDACITY_RULER__
 
+#include "../MemoryX.h"
 #include <wx/bitmap.h>
 #include <wx/dc.h>
 #include <wx/dcmemory.h>
@@ -269,6 +270,8 @@ private:
     DECLARE_EVENT_TABLE()
 };
 
+class QuickPlayIndicatorOverlay;
+
 // This is an Audacity Specific ruler panel which additionally
 // has border, selection markers, play marker.
 // Once TrackPanel uses wxSizers, we will derive it from some
@@ -320,6 +323,7 @@ private:
    void DoDrawCursor(wxDC * dc);
    void DoDrawSelection(wxDC * dc);
    void DoDrawIndicator(wxDC * dc);
+   QuickPlayIndicatorOverlay *GetOverlay();
    void DrawQuickPlayIndicator(wxDC * dc /*NULL to DELETE old only*/);
    void DoDrawPlayRegion(wxDC * dc);
 
@@ -398,6 +402,8 @@ private:
    int mLastMouseX;  // Pixel position
    bool mIsDragging;
 
+   std::unique_ptr<QuickPlayIndicatorOverlay> mOverlay;
+
    DECLARE_EVENT_TABLE()
 };