Add and use some ZoomInfo and ViewInfo member functions, so we can eliminate...

... miscellaneous direct uses of ZoomInfo::zoom to test and set zoom level.

This includes all the remaining assignments to it.

But moving TrackInfo::PositionToTime and TrackInfo::TimeToPosition into
ZoomInfo and using them is needed to eliminate many more uses.

Also #if'd out the unused AudacityProject::OnZoomToggle().

src/ViewInfo.cpp

@@ -10,9 +10,16 @@ Paul Licameli
 
 #include "ViewInfo.h"
 
+#include <algorithm>
+
 #include "Internat.h"
 #include "xml/XMLWriter.h"
 
+namespace {
+static const double gMaxZoom = 6000000;
+static const double gMinZoom = 0.001;
+}
+
 ZoomInfo::ZoomInfo(double start, double screenDuration, double pixelsPerSecond)
    : vpos(0)
    , h(start)
@@ -25,6 +32,46 @@ ZoomInfo::~ZoomInfo()
 {
 }
 
+/// Converts a position (mouse X coordinate) to
+/// project time, in seconds.  Needs the left edge of
+/// the track as an additional parameter.
+double ZoomInfo::PositionToTime(wxInt64 position,
+   wxInt64 origin
+   ) const
+{
+   return h + (position - origin) / zoom;
+}
+
+
+/// STM: Converts a project time to screen x position.
+wxInt64 ZoomInfo::TimeToPosition(double projectTime,
+   wxInt64 origin
+   ) const
+{
+   return floor(0.5 +
+      zoom * (projectTime - h) + origin
+   );
+}
+
+bool ZoomInfo::ZoomInAvailable() const
+{
+   return zoom < gMaxZoom;
+}
+
+bool ZoomInfo::ZoomOutAvailable() const
+{
+   return zoom > gMinZoom;
+}
+
+void ZoomInfo::SetZoom(double pixelsPerSecond)
+{
+   zoom = std::max(gMinZoom, std::min(gMaxZoom, pixelsPerSecond));
+}
+
+void ZoomInfo::ZoomBy(double multiplier)
+{
+   SetZoom(zoom * multiplier);
+}
 
 ViewInfo::ViewInfo(double start, double screenDuration, double pixelsPerSecond)
    : ZoomInfo(start, screenDuration, pixelsPerSecond)
@@ -40,6 +87,14 @@ ViewInfo::ViewInfo(double start, double screenDuration, double pixelsPerSecond)
 {
 }
 
+void ViewInfo::SetBeforeScreenWidth(wxInt64 width, double lowerBoundTime)
+{
+   h =
+      std::max(lowerBoundTime,
+         std::min(total - screen,
+            width / zoom));
+}
+
 void ViewInfo::WriteXMLAttributes(XMLWriter &xmlFile)
 {
    selectedRegion.WriteXMLAttributes(xmlFile, wxT("sel0"), wxT("sel1"));