Stubs needed to eliminate remaining direct uses of ViewInfo::zoom ...

... and anticipate a problems fisheye will introduce with time ruler display
and horizontal scrolling past zero.

Will be used in waveform and spectrogram drawing, and in hit-test for sample
editing.  Those things will no longer make the assumption of uniform zoom
level across the width of the screen, though that does remain true without the
rest of the fisheye project.

src/ViewInfo.cpp

@@ -37,7 +37,8 @@ ZoomInfo::~ZoomInfo()
 /// the track as an additional parameter.
 double ZoomInfo::PositionToTime(wxInt64 position,
    wxInt64 origin
-   ) const
+   , bool // ignoreFisheye
+) const
 {
    return h + (position - origin) / zoom;
 }
@@ -46,7 +47,8 @@ double ZoomInfo::PositionToTime(wxInt64 position,
 /// STM: Converts a project time to screen x position.
 wxInt64 ZoomInfo::TimeToPosition(double projectTime,
    wxInt64 origin
-   ) const
+   , bool // ignoreFisheye
+) const
 {
    return floor(0.5 +
       zoom * (projectTime - h) + origin
@@ -73,6 +75,23 @@ void ZoomInfo::ZoomBy(double multiplier)
    SetZoom(zoom * multiplier);
 }
 
+void ZoomInfo::FindIntervals
+   (double /*rate*/, Intervals &results, wxInt64 origin) const
+{
+   results.clear();
+   results.reserve(2);
+
+   const wxInt64 rightmost(origin + (0.5 + screen * zoom));
+   wxASSERT(origin <= rightmost);
+   {
+      results.push_back(Interval(origin, zoom, false));
+   }
+
+   if (origin < rightmost)
+      results.push_back(Interval(rightmost, 0, false));
+   wxASSERT(!results.empty() && results[0].position == origin);
+}
+
 ViewInfo::ViewInfo(double start, double screenDuration, double pixelsPerSecond)
    : ZoomInfo(start, screenDuration, pixelsPerSecond)
    , selectedRegion()