diff --git a/src/Menus.cpp b/src/Menus.cpp
index b969785ce..2352113de 100644
--- a/src/Menus.cpp
+++ b/src/Menus.cpp
@@ -1770,10 +1770,10 @@ wxUint32 AudacityProject::GetUpdateFlags()
    if (mUndoManager.RedoAvailable())
       flags |= RedoAvailableFlag;
 
-   if (GetZoom() < gMaxZoom && (flags & TracksExistFlag))
+   if (ZoomInAvailable() && (flags & TracksExistFlag))
       flags |= ZoomInAvailableFlag;
 
-   if (GetZoom() > gMinZoom && (flags & TracksExistFlag))
+   if (ZoomOutAvailable() && (flags & TracksExistFlag))
       flags |= ZoomOutAvailableFlag;
 
    if ((flags & LabelTracksExistFlag) && LabelTrack::IsTextClipSupported())
@@ -4882,7 +4882,7 @@ void AudacityProject::ZoomInByFactor( double ZoomFactor )
 {
    // LLL: Handling positioning differently when audio is active
    if (gAudioIO->IsStreamActive(GetAudioIOToken()) != 0) {
-      Zoom(mViewInfo.zoom * ZoomFactor);
+      ZoomBy(ZoomFactor);
       mTrackPanel->ScrollIntoView(gAudioIO->GetStreamTime());
       mTrackPanel->Refresh(false);
       return;
@@ -4915,7 +4915,7 @@ void AudacityProject::ZoomInByFactor( double ZoomFactor )
             (mViewInfo.h + mViewInfo.screen - mViewInfo.selectedRegion.t0()) / 2;
 
       // Zoom in
-      Zoom(mViewInfo.zoom *= ZoomFactor);
+      ZoomBy(ZoomFactor);
 
       // Recenter on selCenter
       TP_ScrollWindow(selCenter - mViewInfo.screen / 2);
@@ -4925,7 +4925,7 @@ void AudacityProject::ZoomInByFactor( double ZoomFactor )
 
    double origLeft = mViewInfo.h;
    double origWidth = mViewInfo.screen;
-   Zoom(mViewInfo.zoom *= ZoomFactor);
+   ZoomBy(ZoomFactor);
 
    double newh = origLeft + (origWidth - mViewInfo.screen) / 2;
 
@@ -4957,7 +4957,7 @@ void AudacityProject::ZoomOutByFactor( double ZoomFactor )
    double origLeft = mViewInfo.h;
    double origWidth = mViewInfo.screen;
 
-   Zoom(mViewInfo.zoom *=ZoomFactor);
+   ZoomBy(ZoomFactor);
 
    double newh = origLeft + (origWidth - mViewInfo.screen) / 2;
    // newh = (newh > 0) ? newh : 0;
@@ -4965,6 +4965,8 @@ void AudacityProject::ZoomOutByFactor( double ZoomFactor )
 
 }
 
+// this is unused:
+#if 0
 static double OldZooms[2]={ 44100.0/512.0, 4410.0/512.0 };
 void AudacityProject::OnZoomToggle()
 {
@@ -4984,11 +4986,12 @@ void AudacityProject::OnZoomToggle()
    double newh = origLeft + (origWidth - mViewInfo.screen) / 2;
    TP_ScrollWindow(newh);
 }
+#endif
 
 
 void AudacityProject::OnZoomNormal()
 {
-   Zoom(44100.0 / 512.0);
+   Zoom(ZoomInfo::GetDefaultZoom());
    mTrackPanel->Refresh(false);
 }
 
@@ -5074,7 +5077,7 @@ void AudacityProject::OnZoomSel()
    //      where the selected region may be scrolled off the left of the screen.
    //      I know this isn't right, but until the real rounding or 1-off issue is
    //      found, this will have to work.
-   Zoom(((mViewInfo.zoom * mViewInfo.screen) - 1) / denom);
+   Zoom((mViewInfo.GetScreenWidth() - 1) / denom);
    TP_ScrollWindow(mViewInfo.selectedRegion.t0());
 }
 
diff --git a/src/Menus.h b/src/Menus.h
index ad0e47cc3..2b5fe80e0 100644
--- a/src/Menus.h
+++ b/src/Menus.h
@@ -259,7 +259,7 @@ void OnSelectAllTracks();
 
 void OnZoomIn();
 void OnZoomOut();
-void OnZoomToggle();
+// void OnZoomToggle();
 void OnZoomNormal();
 void OnZoomFit();
 void OnZoomFitV();
diff --git a/src/Project.cpp b/src/Project.cpp
index ad61d1e10..51b53a068 100644
--- a/src/Project.cpp
+++ b/src/Project.cpp
@@ -780,7 +780,7 @@ AudacityProject::AudacityProject(wxWindow * parent, wxWindowID id,
      mTimerRecordCanceled(false),
      mMenuClose(false)
      , mbInitializingScrollbar(false)
-     , mViewInfo(0.0, 1.0, (44100.0 / 512.0))
+     , mViewInfo(0.0, 1.0, ZoomInfo::GetDefaultZoom())
 {
    // Note that the first field of the status bar is a dummy, and it's width is set
    // to zero latter in the code. This field is needed for wxWidgets 2.8.12 because
@@ -1527,7 +1527,7 @@ void AudacityProject::FixScrollbars()
    double LastTime =
       std::max(mTracks->GetEndTime(), mViewInfo.selectedRegion.t1());
 
-   mViewInfo.screen = ((double) panelWidth) / mViewInfo.zoom;
+   mViewInfo.SetScreenWidth(panelWidth);
    const double halfScreen = mViewInfo.screen / 2.0;
 
    // If we can scroll beyond zero,
@@ -1551,9 +1551,9 @@ void AudacityProject::FixScrollbars()
       rescroll = true;
    }
 
-   mViewInfo.sbarTotal = (wxInt64) (mViewInfo.total * mViewInfo.zoom);
-   mViewInfo.sbarScreen = (wxInt64) (mViewInfo.screen * mViewInfo.zoom);
-   mViewInfo.sbarH = (wxInt64) (mViewInfo.h * mViewInfo.zoom);
+   mViewInfo.sbarTotal = (wxInt64) (mViewInfo.GetTotalWidth());
+   mViewInfo.sbarScreen = (wxInt64) (mViewInfo.GetScreenWidth());
+   mViewInfo.sbarH = (wxInt64) (mViewInfo.GetBeforeScreenWidth());
 
    int lastv = mViewInfo.vpos;
    // PRL:  Can someone else find a more elegant solution to bug 812, than
@@ -1574,7 +1574,7 @@ void AudacityProject::FixScrollbars()
 
    bool oldhstate;
    bool oldvstate;
-   bool newhstate = mViewInfo.screen < mViewInfo.total;
+   bool newhstate = !mViewInfo.ZoomedAll();
    bool newvstate = panelHeight < totalHeight;
 
 #ifdef __WXGTK__
@@ -1585,7 +1585,7 @@ void AudacityProject::FixScrollbars()
 #else
    oldhstate = mHsbar->IsEnabled();
    oldvstate = mVsbar->IsEnabled();
-   mHsbar->Enable(mViewInfo.screen < mViewInfo.total);
+   mHsbar->Enable(!mViewInfo.ZoomedAll());
    mVsbar->Enable(panelHeight < totalHeight);
 #endif
 
@@ -1595,7 +1595,7 @@ void AudacityProject::FixScrollbars()
       refresh = true;
       rescroll = false;
    }
-   if (mViewInfo.screen >= mViewInfo.total && mViewInfo.sbarH != 0) {
+   if (mViewInfo.ZoomedAll() && mViewInfo.sbarH != 0) {
       mViewInfo.sbarH = 0;
 
       refresh = true;
@@ -1638,7 +1638,7 @@ void AudacityProject::FixScrollbars()
                         panelHeight / mViewInfo.scrollStep, TRUE);
    mVsbar->Refresh();
 
-   if (refresh || (rescroll && mViewInfo.screen < mViewInfo.total)) {
+   if (refresh || (rescroll && !mViewInfo.ZoomedAll())) {
       mTrackPanel->Refresh(false);
    }
 
@@ -1821,15 +1821,8 @@ void AudacityProject::OnScroll(wxScrollEvent & WXUNUSED(event))
    mViewInfo.sbarH =
       (wxInt64)(mHsbar->GetThumbPosition() / mViewInfo.sbarScale) - offset;
 
-   if (mViewInfo.sbarH != hlast) {
-      mViewInfo.h = mViewInfo.sbarH / mViewInfo.zoom;
-
-      if (mViewInfo.h > mViewInfo.total - mViewInfo.screen)
-         mViewInfo.h = mViewInfo.total - mViewInfo.screen;
-
-      if (mViewInfo.h < lowerBound)
-         mViewInfo.h = lowerBound;
-   }
+   if (mViewInfo.sbarH != hlast)
+      mViewInfo.SetBeforeScreenWidth(mViewInfo.sbarH, lowerBound);
 
 
    if (mScrollBeyondZero) {
@@ -4117,12 +4110,14 @@ void AudacityProject::SelectNone()
 // Utility function called by other zoom methods
 void AudacityProject::Zoom(double level)
 {
-   if (level > gMaxZoom)
-      level = gMaxZoom;
-   if (level <= gMinZoom)
-      level = gMinZoom;
+   mViewInfo.SetZoom(level);
+   FixScrollbars();
+}
 
-   mViewInfo.zoom = level;
+// Utility function called by other zoom methods
+void AudacityProject::ZoomBy(double multiplier)
+{
+   mViewInfo.ZoomBy(multiplier);
    FixScrollbars();
 }
 
diff --git a/src/Project.h b/src/Project.h
index c741eac83..bd9b1fa12 100644
--- a/src/Project.h
+++ b/src/Project.h
@@ -152,7 +152,8 @@ class AUDACITY_DLL_API AudacityProject:  public wxFrame,
    sampleFormat GetDefaultFormat() { return mDefaultFormat; }
 
    double GetRate() { return mRate; }
-   double GetZoom() { return mViewInfo.zoom; }
+   bool ZoomInAvailable() const { return mViewInfo.ZoomInAvailable(); }
+   bool ZoomOutAvailable() const { return mViewInfo.ZoomOutAvailable(); }
    double GetSel0() { return mViewInfo.selectedRegion.t0(); }
    double GetSel1() { return mViewInfo.selectedRegion.t1(); }
 
@@ -308,6 +309,7 @@ class AUDACITY_DLL_API AudacityProject:  public wxFrame,
    void SelectNone();
    void SelectAllIfNone();
    void Zoom(double level);
+   void ZoomBy(double multiplier);
    void Rewind(bool shift);
    void SkipEnd(bool shift);
    void EditByLabel( WaveTrack::EditFunction action, bool bSyncLockedTracks );
diff --git a/src/Screenshot.cpp b/src/Screenshot.cpp
index 890416132..94fc80c33 100644
--- a/src/Screenshot.cpp
+++ b/src/Screenshot.cpp
@@ -661,7 +661,7 @@ void ScreenFrame::TimeZoom(double seconds)
 {
    int width, height;
    mContext.GetProject()->GetClientSize(&width, &height);
-   mContext.GetProject()->mViewInfo.zoom = (0.75 * width) / seconds;
+   mContext.GetProject()->mViewInfo.SetZoom((0.75 * width) / seconds);
    mContext.GetProject()->RedrawProject();
 }
 
diff --git a/src/TrackPanel.cpp b/src/TrackPanel.cpp
index 4b790b268..5027100f6 100644
--- a/src/TrackPanel.cpp
+++ b/src/TrackPanel.cpp
@@ -4568,15 +4568,11 @@ void TrackPanel::DragZoom(wxMouseEvent & event, int trackLeftEdge)
    double left = PositionToTime(mZoomStart, trackLeftEdge);
    double right = PositionToTime(mZoomEnd, trackLeftEdge);
 
+   double multiplier = mViewInfo->screen / (right - left);
    if (event.ShiftDown())
-      mViewInfo->zoom /= mViewInfo->screen / (right - left);
-   else
-      mViewInfo->zoom *= mViewInfo->screen / (right - left);
+      multiplier = 1.0 / multiplier;
 
-   if (mViewInfo->zoom > gMaxZoom)
-      mViewInfo->zoom = gMaxZoom;
-   if (mViewInfo->zoom <= gMinZoom)
-      mViewInfo->zoom = gMinZoom;
+   mViewInfo->ZoomBy(multiplier);
 
    mViewInfo->h = left;
 }
@@ -4588,13 +4584,13 @@ void TrackPanel::DoZoomInOut(wxMouseEvent & event, int trackLeftEdge)
 {
    double center_h = PositionToTime(event.m_x, trackLeftEdge);
 
-   if (event.RightUp() || event.RightDClick() || event.ShiftDown())
-      mViewInfo->zoom = wxMax(mViewInfo->zoom / 2.0, gMinZoom);
-   else
-      mViewInfo->zoom = wxMin(mViewInfo->zoom * 2.0, gMaxZoom);
+   const double multiplier =
+      (event.RightUp() || event.RightDClick() || event.ShiftDown())
+      ? 0.5 : 2.0;
+   mViewInfo->ZoomBy(multiplier);
 
    if (event.MiddleUp() || event.MiddleDClick())
-      mViewInfo->zoom = 44100.0 / 512.0;        // AS: Reset zoom.
+      mViewInfo->SetZoom(ZoomInfo::GetDefaultZoom()); // AS: Reset zoom.
 
    double new_center_h = PositionToTime(event.m_x, trackLeftEdge);
 
@@ -5301,7 +5297,7 @@ void TrackPanel::UpdateViewIfNoTracks()
    {
       // BG: There are no more tracks on screen
       //BG: Set zoom to normal
-      mViewInfo->zoom = 44100.0 / 512.0;
+      mViewInfo->SetZoom(ZoomInfo::GetDefaultZoom());
 
       //STM: Set selection to 0,0
       //PRL: and default the rest of the selection information
@@ -6322,8 +6318,7 @@ void TrackPanel::HandleWheelRotation(wxMouseEvent & event)
             center_h = audioEndTime;
       }
 
-      // Constrain maximum as well as minimum zoom.
-      mViewInfo->zoom = wxMax( gMinZoom, wxMin(mViewInfo->zoom * pow(2.0, steps), gMaxZoom));
+      mViewInfo->ZoomBy(pow(2.0, steps));
 
       double new_center_h = PositionToTime(xx, trackLeftEdge);
       mViewInfo->h += (center_h - new_center_h);
@@ -8007,11 +8002,14 @@ void TrackPanel::OnToggle()
 // Make sure selection edge is in view
 void TrackPanel::ScrollIntoView(double pos)
 {
+   const int screenWidth = rint(mViewInfo->GetScreenWidth());
+
    int w, h;
    GetTracksUsableArea( &w, &h );
+   // Or should we just set w = screenWidth ?
 
-   if( ( pos < mViewInfo->h ) ||
-       ( pos > mViewInfo->h + ( ( w - 1 ) / mViewInfo->zoom ) ) )
+   int pixel = mViewInfo->TimeToPosition(pos);
+   if (pixel < 0 || pixel >= screenWidth)
    {
       mListener->TP_ScrollWindow( pos - ( ( w / 2 ) / mViewInfo->zoom ) );
       Refresh(false);
@@ -8620,7 +8618,7 @@ void TrackPanel::OnTrackClose()
    if( mTracks->IsEmpty() )
    {
       //BG: Set zoom to normal
-      mViewInfo->zoom = 44100.0 / 512.0;
+      mViewInfo->SetZoom(ZoomInfo::GetDefaultZoom());
 
       //STM: Set selection to 0,0
       //PRL: and default the rest of the selection information
diff --git a/src/ViewInfo.cpp b/src/ViewInfo.cpp
index 33b2ad78e..fbd4e8d46 100644
--- a/src/ViewInfo.cpp
+++ b/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"));
diff --git a/src/ViewInfo.h b/src/ViewInfo.h
index 013006b3d..b9bffac91 100644
--- a/src/ViewInfo.h
+++ b/src/ViewInfo.h
@@ -13,8 +13,6 @@
 
 #include "SelectedRegion.h"
 
-const double gMaxZoom = 6000000,
-             gMinZoom = 0.001;
 
 class Track;
 
@@ -34,6 +32,52 @@ public:
 
    double screen;               // screen width in secs
    double zoom;                 // pixels per second
+
+public:
+
+   // do NOT use this once to convert a pixel width to a duration!
+   // Instead, call twice to convert start and end times,
+   // and take the difference.
+   // origin specifies the pixel corresponding to time h
+   double PositionToTime(wxInt64 position,
+      wxInt64 origin = 0
+      ) const;
+
+   // do NOT use this once to convert a duration to a pixel width!
+   // Instead, call twice to convert start and end positions,
+   // and take the difference.
+   // origin specifies the pixel corresponding to time h
+   wxInt64 TimeToPosition(double time,
+      wxInt64 origin = 0
+      ) const;
+
+   double OffsetTimeByPixels(double time, wxInt64 offset) const
+   {
+      return PositionToTime(offset + TimeToPosition(time));
+   }
+
+   bool ZoomInAvailable() const;
+   bool ZoomOutAvailable() const;
+
+   // Return pixels, but maybe not a whole number
+   double GetScreenWidth() const
+   { return screen * zoom; }
+
+   void SetScreenWidth(wxInt64 width)
+   { screen = width / zoom; }
+
+   static double GetDefaultZoom()
+   { return 44100.0 / 512.0; }
+
+   // There is NO GetZoom()!
+   // Use TimeToPosition and PositionToTime and OffsetTimeByPixels!
+
+   // Limits zoom to certain bounds
+   void SetZoom(double pixelsPerSecond);
+
+   // Limits zoom to certain bounds
+   // multipliers above 1.0 zoom in, below out
+   void ZoomBy(double multiplier);
 };
 
 class AUDACITY_DLL_API ViewInfo
@@ -42,6 +86,18 @@ class AUDACITY_DLL_API ViewInfo
 public:
    ViewInfo(double start, double screenDuration, double pixelsPerSecond);
 
+   double GetBeforeScreenWidth() const
+   {
+      return h * zoom;
+   }
+   void SetBeforeScreenWidth(wxInt64 width, double lowerBoundTime = 0.0);
+
+   double GetTotalWidth() const
+   { return total * zoom; }
+
+   bool ZoomedAll() const
+   { return screen >= total; }
+
    // Current selection
 
    SelectedRegion selectedRegion;
diff --git a/src/import/ImportLOF.cpp b/src/import/ImportLOF.cpp
index 9bd2d999f..fb1d0ad1c 100644
--- a/src/import/ImportLOF.cpp
+++ b/src/import/ImportLOF.cpp
@@ -70,6 +70,7 @@
 *//*******************************************************************/
 
 #include "../Audacity.h"
+#include "ImportLOF.h"
 
 #include <wx/string.h>
 #include <wx/utils.h>
@@ -78,7 +79,6 @@
 #include <wx/msgdlg.h>
 #include <wx/tokenzr.h>
 
-#include "ImportLOF.h"
 #ifdef USE_MIDI
 #include "ImportMIDI.h"
 #endif // USE_MIDI
@@ -485,8 +485,7 @@ void LOFImportFileHandle::doDuration()
    if (callDurationFactor)
    {
       double longestDuration = mProject->GetTracks()->GetEndTime();
-      double realZoomValue = ((longestDuration/durationFactor)*(mProject->GetZoom()));
-      mProject->Zoom(realZoomValue);
+      mProject->ZoomBy(longestDuration / durationFactor);
       callDurationFactor = false;
    }
 }
diff --git a/src/toolbars/EditToolBar.cpp b/src/toolbars/EditToolBar.cpp
index b314388d9..16237ed01 100644
--- a/src/toolbars/EditToolBar.cpp
+++ b/src/toolbars/EditToolBar.cpp
@@ -32,6 +32,7 @@
 
 
 #include "../Audacity.h"
+#include "EditToolBar.h"
 
 // For compilers that support precompilation, includes "wx/wx.h".
 #include <wx/wxprec.h>
@@ -44,8 +45,6 @@
 #include <wx/tooltip.h>
 #endif
 
-#include "EditToolBar.h"
-
 #include "../AllThemeResources.h"
 #include "../AudioIO.h"
 #include "../ImageManipulation.h"
@@ -308,8 +307,8 @@ void EditToolBar::EnableDisableButtons()
 
    bool tracks = (!p->GetTracks()->IsEmpty());
 
-   mButtons[ETBZoomInID]->SetEnabled(tracks && (p->GetZoom() < gMaxZoom));
-   mButtons[ETBZoomOutID]->SetEnabled(tracks && (p->GetZoom() > gMinZoom) );
+   mButtons[ETBZoomInID]->SetEnabled(tracks && (p->ZoomInAvailable()));
+   mButtons[ETBZoomOutID]->SetEnabled(tracks && (p->ZoomOutAvailable()) );
 
    #if 0 // Disabled for version 1.2.0 since it doesn't work quite right...
    mButtons[ETBZoomToggleID]->SetEnabled(tracks);
diff --git a/src/widgets/AttachableScrollBar.cpp b/src/widgets/AttachableScrollBar.cpp
index 241201254..5ffb2fefd 100644
--- a/src/widgets/AttachableScrollBar.cpp
+++ b/src/widgets/AttachableScrollBar.cpp
@@ -28,9 +28,9 @@ internally, not ints, allowing for (external) control of zooming.
 *//*******************************************************************/
 
 #include "../Audacity.h"
+#include "AttachableScrollBar.h"
 
 #include <wx/wxprec.h>
-#include "AttachableScrollBar.h"
 #include "../ViewInfo.h"
 
 
@@ -58,9 +58,9 @@ void AttachableScrollBar::SetScrollBarFromViewInfo()
 {
    ViewInfo & mViewInfo = *mpViewInfo;
 
-   mViewInfo.sbarTotal = (int) (mViewInfo.total * mViewInfo.zoom);
-   mViewInfo.sbarScreen = (int) (mViewInfo.screen * mViewInfo.zoom);
-   mViewInfo.sbarH = (int) (mViewInfo.h * mViewInfo.zoom);
+   mViewInfo.sbarTotal = (int) (mViewInfo.GetTotalWidth());
+   mViewInfo.sbarScreen = (int) (mViewInfo.GetScreenWidth());
+   mViewInfo.sbarH = (int) (mViewInfo.GetBeforeScreenWidth());
 
    SetScrollbar(mViewInfo.sbarH, mViewInfo.sbarScreen,
                         mViewInfo.sbarTotal, mViewInfo.sbarScreen, TRUE);
@@ -75,14 +75,8 @@ void AttachableScrollBar::SetViewInfoFromScrollBar()
 
    mViewInfo.sbarH = GetThumbPosition();
 
-   if (mViewInfo.sbarH != hlast) {
-      mViewInfo.h = mViewInfo.sbarH / mViewInfo.zoom;
-
-      if (mViewInfo.h > mViewInfo.total - mViewInfo.screen)
-         mViewInfo.h = mViewInfo.total - mViewInfo.screen;
-      if (mViewInfo.h < 0.0)
-         mViewInfo.h = 0.0;
-   }
+   if (mViewInfo.sbarH != hlast)
+      mViewInfo.SetBeforeScreenWidth(mViewInfo.sbarH);
 }
 
 // Used to associated a ViewInfo structure with a scrollbar.