Bug977: Enable new scrolling limits as a Tracks preference, default off.

src/Project.cpp

@@ -767,6 +767,7 @@ AudacityProject::AudacityProject(wxWindow * parent, wxWindowID id,
      mIsDeleting(false),
      mTracksFitVerticallyZoomed(false),  //lda
      mShowId3Dialog(true),               //lda
+     mScrollBeyondZero(false),
      mLastFocusedWindow(NULL),
      mKeyboardCaptured(NULL),
      mImportXMLTagHandler(NULL),
@@ -1060,6 +1061,9 @@ AudioIOStartStreamOptions AudacityProject::GetDefaultPlayOptions()
 
 void AudacityProject::UpdatePrefsVariables()
 {
+#ifdef EXPERIMENTAL_SCROLLING_LIMITS
+   gPrefs->Read(wxT("/GUI/ScrollBeyondZero"), &mScrollBeyondZero, false);
+#endif
    gPrefs->Read(wxT("/AudioFiles/ShowId3Dialog"), &mShowId3Dialog, true);
    gPrefs->Read(wxT("/AudioFiles/NormalizeOnLoad"),&mNormalizeOnLoad, false);
    gPrefs->Read(wxT("/GUI/AutoScroll"), &mViewInfo.bUpdateTrackIndicator, true);
@@ -1457,10 +1461,7 @@ void AudacityProject::OnScrollRightButton(wxScrollEvent & event)
 
 void AudacityProject::SetHorizontalThumb(double scrollto)
 {
-   double timeOffset = 0;
-#ifdef EXPERIMENTAL_SCROLLING_LIMITS
-   timeOffset = mViewInfo.screen / 2.0;
-#endif
+   const double timeOffset = mScrollBeyondZero ? mViewInfo.screen / 2.0 : 0;
    int pos = (int) (
       (scrollto + timeOffset) * mViewInfo.zoom * mViewInfo.sbarScale
    );
@@ -1536,20 +1537,18 @@ void AudacityProject::FixScrollbars()
 
    mViewInfo.screen = ((double) panelWidth) / mViewInfo.zoom;
    const double halfScreen = mViewInfo.screen / 2.0;
-   double additional, lowerBound;
-#ifdef EXPERIMENTAL_SCROLLING_LIMITS
+
+   // If we can scroll beyond zero,
    // Add 1/2 of a screen of blank space to the end
    // and another 1/2 screen before the beginning
    // so that any point within the union of the selection and the track duration
    // may be scrolled to the midline.
    // May add even more to the end, so that you can always scroll the starting time to zero.
-   additional = halfScreen + std::max(halfScreen, mViewInfo.screen - LastTime);
-   lowerBound = - halfScreen;
-#else
-   // Formerly just added 1/4 screen at the end
-   additional = mViewInfo.screen / 4.0;
-   lowerBound = 0.0;
-#endif
+   const double additional = mScrollBeyondZero
+      ? halfScreen + std::max(halfScreen, mViewInfo.screen - LastTime)
+      : mViewInfo.screen / 4.0;
+   const double lowerBound = mScrollBeyondZero ? -halfScreen : 0.0;
+
    mViewInfo.total = LastTime + additional;
 
    // Don't remove time from total that's still on the screen
@@ -1822,17 +1821,14 @@ void AudacityProject::OnODTaskComplete(wxCommandEvent & WXUNUSED(event))
 
 void AudacityProject::OnScroll(wxScrollEvent & WXUNUSED(event))
 {
-   wxInt64 hlast = mViewInfo.sbarH;
+   const wxInt64 hlast = mViewInfo.sbarH;
+
+   const wxInt64 offset = mScrollBeyondZero
+      ? (0.5 + (mViewInfo.zoom * mViewInfo.screen / 2.0))
+      : 0.0;
+   const double lowerBound = mScrollBeyondZero
+      ? -mViewInfo.screen / 2.0 : 0.0;
 
-   double lowerBound;
-   wxInt64 offset;
-#ifdef EXPERIMENTAL_SCROLLING_LIMITS
-   offset = (0.5 + (mViewInfo.zoom * mViewInfo.screen / 2.0));
-   lowerBound = -mViewInfo.screen / 2.0;
-#else
-   offset = 0.0;
-   lowerBound = 0.0;
-#endif
    mViewInfo.sbarH =
       (wxInt64)(mHsbar->GetThumbPosition() / mViewInfo.sbarScale) - offset;
 
@@ -1846,14 +1842,15 @@ void AudacityProject::OnScroll(wxScrollEvent & WXUNUSED(event))
          mViewInfo.h = lowerBound;
    }
 
-#ifdef EXPERIMENTAL_SCROLLING_LIMITS
-   enum { SCROLL_PIXEL_TOLERANCE = 10 };
-   if (fabs(mViewInfo.h * mViewInfo.zoom) < SCROLL_PIXEL_TOLERANCE) {
-      // Snap the scrollbar to 0
-      mViewInfo.h = 0;
-      SetHorizontalThumb(0.0);
+
+   if (mScrollBeyondZero) {
+      enum { SCROLL_PIXEL_TOLERANCE = 10 };
+      if (fabs(mViewInfo.h * mViewInfo.zoom) < SCROLL_PIXEL_TOLERANCE) {
+         // Snap the scrollbar to 0
+         mViewInfo.h = 0;
+         SetHorizontalThumb(0.0);
+      }
    }
-#endif
 
    int lastv = mViewInfo.vpos;
    mViewInfo.vpos = mVsbar->GetThumbPosition() * mViewInfo.scrollStep;

src/Project.h

@@ -576,6 +576,9 @@ class AUDACITY_DLL_API AudacityProject:  public wxFrame,
    bool mNormalizeOnLoad;  //lda
    bool mShowId3Dialog; //lda
    bool mEmptyCanBeDirty;
+
+   bool mScrollBeyondZero;
+
    bool mSelectAllOnNone;
 
    bool mIsSyncLocked;

src/TrackPanel.cpp

@@ -830,6 +830,9 @@ void TrackPanel::UpdateVirtualStereoOrder()
 
 void TrackPanel::UpdatePrefs()
 {
+#ifdef EXPERIMENTAL_SCROLLING_LIMITS
+   gPrefs->Read(wxT("/GUI/ScrollBeyondZero"), &mScrollBeyondZero, false);
+#endif
    mdBr = gPrefs->Read(wxT("/GUI/EnvdBRange"), ENV_DB_RANGE);
    gPrefs->Read(wxT("/GUI/AutoScroll"), &mViewInfo->bUpdateTrackIndicator,
                true);
@@ -1488,10 +1491,9 @@ void TrackPanel::OnPaint(wxPaintEvent & /* event */)
          // at higher magnifications, and keeps the green line still in the middle.
          indicator = gAudioIO->GetStreamTime();
          mViewInfo->h = indicator - mViewInfo->screen / 2.0;
-#if !defined(EXPERIMENTAL_SCROLLING_LIMITS)
-         // Can't scroll too far left
-         mViewInfo->h = std::max(0.0, mViewInfo->h);
-#endif
+         if (!mScrollBeyondZero)
+            // Can't scroll too far left
+            mViewInfo->h = std::max(0.0, mViewInfo->h);
       }
 #endif
 

src/TrackPanel.h

@@ -766,6 +766,7 @@ protected:
    enum MouseCaptureEnum mMouseCapture;
    virtual void SetCapturedTrack( Track * t, enum MouseCaptureEnum MouseCapture=IsUncaptured );
 
+   bool mScrollBeyondZero;
    bool mAdjustSelectionEdges;
    bool mSlideUpDownOnly;
    bool mCircularTrackNavigation;

src/prefs/TracksPrefs.cpp

@@ -18,13 +18,13 @@
 *//*******************************************************************/
 
 #include "../Audacity.h"
+#include "TracksPrefs.h"
 
 #include <wx/defs.h>
 
+#include "../Experimental.h"
 #include "../ShuttleGui.h"
 
-#include "TracksPrefs.h"
-
 ////////////////////////////////////////////////////////////////////////////////
 
 TracksPrefs::TracksPrefs(wxWindow * parent)
@@ -116,6 +116,11 @@ void TracksPrefs::PopulateOrExchange(ShuttleGui & S)
       S.TieCheckBox(_("Editing a clip can &move other clips"),
                     wxT("/GUI/EditClipCanMove"),
                     true);
+#ifdef EXPERIMENTAL_SCROLLING_LIMITS
+      S.TieCheckBox(_("Enable scrolling left of &zero"),
+                    wxT("/GUI/ScrollBeyondZero"),
+                    false);
+#endif
 
       S.AddSpace(10);