Use XDG_CONFIG_DIR for lock file path on Linux.

* With fixes from Adam Wolf.

common/common.cpp

 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2014 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 2008-2011 Wayne Stambaugh <stambaughw@verizon.net>
- * Copyright (C) 1992-2011 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2014-2015 Jean-Pierre Charras, jp.charras at wanadoo.fr
+ * Copyright (C) 2008-2015 Wayne Stambaugh <stambaughw@verizon.net>
+ * Copyright (C) 1992-2015 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -271,9 +271,9 @@ double RoundTo0( double x, double precision )
 
     int remainder = ix % 10;   // remainder is in precision mm
 
-    if ( remainder <= 2 )
+    if( remainder <= 2 )
         ix -= remainder;       // truncate to the near number
-    else if (remainder >= 8 )
+    else if( remainder >= 8 )
         ix += 10 - remainder;  // round to near number
 
     if ( x < 0 )
@@ -305,6 +305,46 @@ wxConfigBase* GetNewConfig( const wxString& aProgName )
     return cfg;
 }
 
+wxString GetKicadLockFilePath()
+{
+    wxFileName lockpath;
+    lockpath.AssignDir( wxGetHomeDir() ); // Default wx behavior
+
+#if defined( __WXMAC__ )
+    // In OSX use the standard per user cache directory
+    lockpath.AppendDir( wxT( "Library" ) );
+    lockpath.AppendDir( wxT( "Caches" ) );
+    lockpath.AppendDir( wxT( "kicad" ) );
+#elif defined( __UNIX__ )
+    wxString envstr;
+    // Try first the standard XDG_RUNTIME_DIR, falling back to XDG_CACHE_HOME
+    if( wxGetEnv( wxT( "XDG_RUNTIME_DIR" ), &envstr ) && !envstr.IsEmpty() )
+    {
+        lockpath.AssignDir( envstr );
+    }
+    else if( wxGetEnv( wxT( "XDG_CACHE_HOME" ), &envstr ) && !envstr.IsEmpty() )
+    {
+        lockpath.AssignDir( envstr );
+    }
+    else
+    {
+        // If all fails, just use ~/.cache
+        lockpath.AppendDir( wxT( ".cache" ) );
+    }
+
+    lockpath.AppendDir( wxT( "kicad" ) );
+#endif
+
+#if defined( __WXMAC__ ) || defined( __UNIX__ )
+    if( !lockpath.DirExists() )
+    {
+        // Lockfiles should be only readable by the user
+        lockpath.Mkdir( 0700, wxPATH_MKDIR_FULL );
+    }
+#endif
+    return lockpath.GetPath();
+}
+
 
 wxString GetKicadConfigPath()
 {

common/lockfile.cpp

 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2014 SoftPLC Corporation, Dick Hollenbeck <dick@softplc.com>
- * Copyright (C) 2014 KiCad Developers, see CHANGELOG.TXT for contributors.
+ * Copyright (C) 2014-2015 SoftPLC Corporation, Dick Hollenbeck <dick@softplc.com>
+ * Copyright (C) 2014-2015 KiCad Developers, see CHANGELOG.TXT for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -24,6 +24,7 @@
 
 #include <wx/filename.h>
 #include <wx/snglinst.h>
+#include <common.h>
 
 
 wxSingleInstanceChecker* LockFile( const wxString& aFileName )
@@ -41,7 +42,8 @@ wxSingleInstanceChecker* LockFile( const wxString& aFileName )
     // We can have filenames coming from Windows, so also convert Windows separator
     lockFileName.Replace( wxT( "\\" ), wxT( "_" ) );
 
-    wxSingleInstanceChecker* p = new wxSingleInstanceChecker( lockFileName );
+    wxSingleInstanceChecker* p = new wxSingleInstanceChecker( lockFileName,
+                                                              GetKicadLockFilePath() );
 
     if( p->IsAnotherRunning() )
     {

common/pgm_base.cpp

 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2004 Jean-Pierre Charras, jaen-pierre.charras@gipsa-lab.inpg.com
- * Copyright (C) 2008-2011 Wayne Stambaugh <stambaughw@verizon.net>
- * Copyright (C) 1992-2011 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2004-2015 Jean-Pierre Charras, jaen-pierre.charras@gipsa-lab.inpg.com
+ * Copyright (C) 2008-2015 Wayne Stambaugh <stambaughw@verizon.net>
+ * Copyright (C) 1992-2015 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -353,7 +353,7 @@ bool PGM_BASE::initPgm()
 
     wxInitAllImageHandlers();
 
-    m_pgm_checker = new wxSingleInstanceChecker( pgm_name.GetName().Lower() + wxT( "-" ) + wxGetUserId() );
+    m_pgm_checker = new wxSingleInstanceChecker( pgm_name.GetName().Lower() + wxT( "-" ) + wxGetUserId(), GetKicadLockFilePath() );
 
     if( m_pgm_checker->IsAnotherRunning() )
     {

include/common.h

 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2013 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 2007-2013 SoftPLC Corporation, Dick Hollenbeck <dick@softplc.com>
- * Copyright (C) 2008-2013 Wayne Stambaugh <stambaughw@verizon.net>
- * Copyright (C) 1992-2013 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2014-2015 Jean-Pierre Charras, jp.charras at wanadoo.fr
+ * Copyright (C) 2007-2015 SoftPLC Corporation, Dick Hollenbeck <dick@softplc.com>
+ * Copyright (C) 2008-2015 Wayne Stambaugh <stambaughw@verizon.net>
+ * Copyright (C) 1992-2015 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -278,7 +278,7 @@ bool EnsureTextCtrlWidth( wxTextCtrl* aCtrl, const wxString* aString = NULL );
  *               wxExecute())
  */
 int ProcessExecute( const wxString& aCommandLine, int aFlags = wxEXEC_ASYNC,
-                     wxProcess *callback = NULL );
+                    wxProcess *callback = NULL );
 
 
 /*******************/
@@ -433,6 +433,12 @@ const wxString PrePendPath( const wxString& aEnvVar, const wxString& aPriorityPa
  */
 wxConfigBase* GetNewConfig( const wxString& aProgName );
 
+/**
+ * Function GetKicadLockFilePath
+ * @return A wxString containing the path for lockfiles in Kicad
+ */
+wxString GetKicadLockFilePath();
+
 /**
  * Function GetKicadConfigPath
  * @return A wxString containing the config path for Kicad