From 8886d1ba41fb3875535cab9f75d0868002c4760b Mon Sep 17 00:00:00 2001
From: James Crook <james.k.crook@gmail.com>
Date: Mon, 22 Aug 2016 13:25:05 +0100
Subject: [PATCH] Bug 1487 - Scrub and Seek are enabled when there is no audio
 to operate on

I added a new flag, HasWaveDataFlag that checks not only for the presence  of a WaveTrack but also for audio actually in it.  This is now applied to the Scrub and Seek menu items, with the result that they grey out in the menu, and their buttons are dulled on the toolbar, if there is no audio.
---
 src/AudacityApp.h           | 1 +
 src/Menus.cpp               | 2 ++
 src/tracks/ui/Scrubbing.cpp | 6 ++++--
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/AudacityApp.h b/src/AudacityApp.h
index ec888568a..4eacac2fc 100644
--- a/src/AudacityApp.h
+++ b/src/AudacityApp.h
@@ -97,6 +97,7 @@ enum CommandFlag : unsigned long long
    NotMinimizedFlag      = 0x100000000ULL, // prl
    PausedFlag            = 0x200000000ULL, // jkc
    NotPausedFlag         = 0x400000000ULL, // jkc
+   HasWaveDataFlag       = 0x800000000ULL, // jkc
 
    NoFlagsSpecifed        = ~0ULL
 };
diff --git a/src/Menus.cpp b/src/Menus.cpp
index 425120602..cfdfb9e8a 100644
--- a/src/Menus.cpp
+++ b/src/Menus.cpp
@@ -1736,6 +1736,8 @@ CommandFlag AudacityProject::GetUpdateFlags()
                flags |= WaveTracksSelectedFlag;
             }
          }
+         if( t->GetEndTime() > t->GetStartTime() )
+            flags |= HasWaveDataFlag; 
       }
 #if defined(USE_MIDI)
       else if (t->GetKind() == Track::Note) {
diff --git a/src/tracks/ui/Scrubbing.cpp b/src/tracks/ui/Scrubbing.cpp
index c32b61c26..310e195c5 100644
--- a/src/tracks/ui/Scrubbing.cpp
+++ b/src/tracks/ui/Scrubbing.cpp
@@ -233,12 +233,12 @@ namespace {
          "Seeking" is normal speed playback but with skips, ...
        */
       { wxT("Scrub"),       XO("&Scrub"),           XO("Scrubbing"),
-         CaptureNotBusyFlag,
+         CaptureNotBusyFlag | HasWaveDataFlag,
          &Scrubber::OnScrub,       false,      &Scrubber::Scrubs,
       },
 
       { wxT("Seek"),        XO("See&k"),            XO("Seeking"),
-         CaptureNotBusyFlag,
+         CaptureNotBusyFlag | HasWaveDataFlag,
          &Scrubber::OnSeek,        true,       &Scrubber::Seeks,
       },
 
@@ -859,6 +859,8 @@ Scrubber &ScrubbingOverlay::GetScrubber()
 
 void Scrubber::DoScrub(bool seek)
 {
+   if( !CanScrub() )
+      return;
    const bool wasScrubbing = HasStartedScrubbing() || IsScrubbing();
    const bool scroll = TracksPrefs::GetPinnedHeadPreference();
    if (!wasScrubbing) {