Rework the ESC key to stop playback as an application event handler...

... So it does not depend on the focused window, and can work when selection
toolbar has focus.  But TrackPanel's escape handling may still take precedence
over it.

src/AudacityApp.cpp

@@ -113,6 +113,8 @@ It handles initialization and termination by subclassing wxApp.
 #include "effects/ScoreAlignDialog.h"
 #endif
 
+#include "tracks/ui/Scrubbing.h"
+
 #if 0
 #ifdef _DEBUG
     #ifdef _MSC_VER
@@ -766,6 +768,9 @@ BEGIN_EVENT_TABLE(AudacityApp, wxApp)
 
    // Handle AppCommandEvents (usually from a script)
    EVT_APP_COMMAND(wxID_ANY, AudacityApp::OnReceiveCommand)
+
+   // Global ESC key handling
+   EVT_KEY_DOWN(AudacityApp::OnKeyDown)
 END_EVENT_TABLE()
 
 // backend for OnMRUFile
@@ -1519,7 +1524,29 @@ void AudacityApp::OnReceiveCommand(AppCommandEvent &event)
    mCmdHandler->OnReceiveCommand(event);
 }
 
-// We now disallow temp directory name that puts it where cleaner apps will 
+void AudacityApp::OnKeyDown(wxKeyEvent &event)
+{
+   if(event.GetKeyCode() == WXK_ESCAPE) {
+      // Stop play, including scrub, but not record
+      auto project = ::GetActiveProject();
+      auto token = project->GetAudioIOToken();
+      auto &scrubber = project->GetScrubber();
+      if(scrubber.HasStartedScrubbing())
+         // ESC out of scrubbing
+         scrubber.StopScrubbing();
+      else if(token > 0 &&
+              gAudioIO->IsAudioTokenActive(token) &&
+              gAudioIO->GetNumCaptureChannels() == 0)
+         // ESC out of other play (but not record)
+         project->OnStop();
+      else
+         event.Skip();
+   }
+   else
+      event.Skip();
+}
+
+// We now disallow temp directory name that puts it where cleaner apps will
 // try to clean out the files.  
 bool AudacityApp::IsTempDirectoryNameOK( const wxString & Name ){
 #ifndef  __WXMSW__